Aht#wHotl5MUSEUM OF NATURAL HISTORY PUBLICATION FOR EDUCATORS ?VOLUME 31 NO. 1 SPRING 2010WHAT DOES IT MEAN TO BE HUMAN?A BEHAVIORAL PERSPECTIVE
by Alison S. Brooks MAR 1 9 Z013
"...// would be impossible tofix on anypointwhen the term "man"ought to be used " (Darwin 1 871 : 230)Anew permanent exhibit at the Smithsonian's Na-tional Museum ofNatural History asks the ques-tion "What does it mean to be human?" Beforethere were any fossils to inform us about the roads takenand not taken on our evolutionary journey, 18 th and 19 thcentury scholars wresded with the anatomical similaritiesbetween humans and apes, especially, as Darwin noted,the African apes. Many of the human distinctions theseearly scholars cited were behavioral, including language,tool-making and technology-dependence, culture, use offixe, a sense of shame, burial of the dead, and a sense ofthe sacred. Even today, our anatomy alone may not suf-fice to define our genus Homo. Indeed in 1 964 one of theoldest members of our genus, Homo babilis, was definedas Homo to a large extent on the basis of the tools foundin association with its bones; the evolutionary or genericstatus of the bones themselves remains controversial. Asin the museum's new exhibit, new approaches to under-standing our past and defining our species emphasize the
role of changing human behavior and its relationship toand possible role in changing our anatomy.This paper offers a brief summary of key discover-ies in the fossil record followed by a discussion of be-havioral characteristics defining modern humans and theiremergence through time. This is followed by a descrip-tion of the evidence documenting the development ofarchaic, Neanderthal, and modern humans, tracing theevolution ofkey behaviors from 600 kya to 40 kya (thou-sands of years ago). Finally, the evidence for the role ofAfrica in the gradual evolution of distincdy modern hu-man behaviors is argued as the paper concludes.The Fossil Record of Human EvolutionCharles Darwin in his 1871 book, The Descent ofMan,located the likely origination ofhumans in Africa due tothe geographic distribution and comparable anatomy ofthe chimpanzee and gorilla. Other early scholars, how-ever, thought that our two most distinctive anatomicalfeatures, our large brains and our two-legged gait, hadevolved together and that these changes had happened inEurope. In Darwin's time, only a few fossils of Nean-
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derthals, our closest extinct relatives, had been recoveredfrom European sites. The 1 891 finding inJava of Pithecan-thropus erectus (now Homo erectus), an upright biped with acranial capacity of only 900cc, argued that both of theseideas were false; bipedalism came first and not in Europe.Only much later in 1924 were the first African fossils ofhuman ancestors recovered at Singa (Sudan) and Taung(South Africa). The ca. 2-2.5 million-year-old Taung speci-men of a small child with a chimpanzee-sized brain be-came the type fossil ofAustralopithecus (Dart 1925), a genusthat is probably ancestral to our own {Homo). Like the Pith-ecanthropus discovery, the Taung child's human-like teeth,small brain but upright posture, as indicated by the posi-tion of the skull on top of the spine, suggested that braindevelopment lagged behind new ways of getting around.Most scholars in the 1 920s, and some much more re-cently, continued to argue that major changes in the humanevolutionary past occurred in Eurasia. But since the 1920s,Pliocene and Pleistocene age (5.3 ? 0.01 million years agoor mya) fossil specimens belonging in the hominin lin-eage?representing more than 6,000 individuals?havebeen recovered at an accelerating pace from Europe, Asia,Africa, and Australia. Africa has yielded the oldest mem-bers of the human lineage ("hominins"), the oldest stonetools, the oldest members of our genus Homo, and theoldest members of our species Homo sapiens. Multiple ge-netic studies of modern human mitochondrial Y-chromo-some and nuclear DNA conclude that the greatest vari-
ability, the most ancestral lineages, and the likely region oforigin are all African, proving that Darwin was right inassigning us an African origin.The emergence of a richer fossil record raises anewthe question, what do we mean by human? Are the earliesthominin fossils from 7-3 mya whose skeletons reflect somelevel of bipedal locomotion human? (See accompanying
article on the development of bipedalism.) Does the ge-nus Homo begin with the appearance of stone tools 2.6mya, or with the first reduction in molar size around 2.3mya, or with the first signs of brain enlargement in Ethio-pian and Kenyan fossils from 1.9 mya? Should we onlybestow the word "human" (or the generic/evolutionarystatus of Homo) on fossils with the human-like suite ofcharacteristics reflected in the relatively complete skeletonof the 1 .5 mya "Turkana Boy." Found in northern Kenya,this fossil had a brain almost 2/3 the size of ours, smaller
teeth than in previous hominins, and modern body sizeand limb proportions reflecting fully-committed bipedalwalking and running. Should we limit the definition of "fullyhuman" only to members of the species Homo sapiens, de-fined morphologically by large brains in relation to body
size, small teeth, gracile skeletons, chins, minimal browridges, vertical foreheads, and faces tucked under brain-cases in such a way as to facilitate speech? Or perhaps onlyto those members of our species who demonstrated ad-vanced abilities for symbolic behavior, innovation, and socialcomplexity?A Behavioral PerspectiveLike the expanding fossil record, studies of great apes inthe wild have documented many human-like behaviors,blurring humans' behavioral distinctiveness. All the greatapes make and use simple tools, and their tool use andother behaviors vary among populations, suggesting thatgroups invent and hand down different behaviors fromone generation to the next, a rudimentary form of 'cul-ture.' While spoken language is still a major defining featureof humans, many humans use other forms of communi-cation, and some apes have proven capable of learningfrom humans or even from each other to communicateusing elements of sign language. Psychologists focus onthe expression, in humans, of such characters as "empa-thy" and "problem-solving abilities." However, in almostevery case, at least one of the great apes (or some otheranimal) has shown this feature in some form. An absolutedistinction between humans and non-human animals hasthus far proved elusive.What can the fossil and archaeological records tell usabout the evolution ofhuman behavior? Even before thereare any tools or archaeological sites, the fossils themselvesreflect behavior in the shape of bones, the position andstrength of muscle markings, the form of the teeth, thepatterning of reinforcing structure inside the bone and itschemical composition, as well as in signs oftrauma over alifetime. The long arms, curved fingers and toes, and up-wardly-oriented shoulder joint ofAustralopithecus reflect alife still lived partially in the trees. Small canines suggest anew, less confrontational approach to male-male relation-ships and social organization, whilechemical studies oftheteeth suggest that later ones may have begun to exploit thesame foods that make up large parts of the human diet ?meat and tubers. The reconstructed environments of the
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sites themselves also tell a story?of early use by homininsof a wide range of environments both in and out of theforest.Between 2.6 and 2.3 million years ago in Ethiopia andKenya, along with Australopithecus and some fossils withslightly smaller teeth and shorter faces attributed on thatbasis to Homo, we begin to find material remains in theform of flaked stone tools and bones that were cut andbroken open to access meat and marrow. Such archaeo-logical sites are formed through human activities, althoughit has been shown that chimpan2ees also leave archaeologi-cal traces of their behavior.The fossil and archaeological records are limited in whatthey can say about the origins of humans, as they requiredefinitions ofhumanness that are amenable to recovery inthe material record. For example, one cannot recover fos-
sil languages, at least not until the development of writing.But one can recover traces of symbolic behavior, or mor-phological traces of changes in brain or vocal tract mor-phology that suggest an ability for language. Ideologies orthe capacity for abstract thought are not preserved, butone can recover traces of practices that seem to conformto ideas about spirituality?burial of the dead and cave art.Problem solving and creative innovation cannot be directlyobserved in the past, but one can document increases intechnological sophistication and rates ofinnovation. Socialnetworks and societies in which humans live are abstrac-tions that must be inferred from physical evidence even inliving populations. But through geochemical analysis ofwhere raw materials came from, one can trace the move-ment of materials like stone and beads over very long dis-tances and thereby infer human networks' size and distance.In addition, from patterns ofvariability in the materialrecord, it is possible to infer whether or not people distin-guished themselves from their neighbors through theirmaterial culture, and what the size ofthe distinctive group-ings might have been. Signs of empathy may also be evi-dent in the survival of individuals with crippling injuries ormajor deficits, who could not have survived long on theirown.Defining Human BehaviorFrom the perspective ofmodern humans, behavioral defi-nitions ofhumanness include what can be considered "liv-ing in our heads," enabling us to transform the natural world.
Multipurpose tools, such as hand axes, used to chopwood, butcher animals, and make other tools , dominatedearly human technology for more than a million years. Leftto right: Africa (1.6 million years old), Asia (1.1 millionyears old), and Europe (250,000 years old). Photo courtesyHuman Origins Program.Humans think up cultural solutions to scarcity, risk, and thequest for food, shelter and mates, resulting in an astound-ing diversity of cultural forms and the transformation ofvast areas of the earth's surface. Since humans' teeth andtheir two-legged gait are utterly inadequate for defenseagainst natural predators, humans are totally dependent oninvented technologies. Rather than living in a physical herdor a pack, humans live in what have been called "imaginedcommunities," populated by individuals never physicallyencountered?distant relatives, compatriots, ancestors, and
spiritual beings. Humans use symbols extensively to repre-sent themselves, their social groups, and their thoughts. Hu-mans have the ability to imagine the feelings and lives ofothers as both separate from and similar to their own?ina way that leads to extraordinary capacities for altruismand sympathy, even for individuals they may never meet.One way to describe the capabilities of modern hu-mans is to separate out at least six different faculties:Abstract thinking, the ability to act with reference toconcepts not limited in time and space. A chimpanzee canbe taught to use symbols correctly to solicit a reward, butnot to go to the grocery store with a shopping list andremember that she forgot to write down the bananas.
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Planning depth: the ability to strategize in a group con-text. Social carnivores share this ability in the immediatefuture, but lack our ability to plan for next year, or forcontingencies that may never happen.Problem-solving through behavioral, economic, and technologi-
cal innovation: Many animals are good problem solvers, butmodern humans solve problems that have not yet arisenand devise entirely new ways of living in the process.Imagined communities: Our present communities, fromfamily to nation, may include people we have never met,
spirits, animals, and people who have died and the not-yet-born. These communities exist in our heads and never meetface-to-face as a group.Symbolic thinking: Especially with regard to informa-tion storage, this involves the ability to reference both physi-cal objects/beings and ideas with arbitrary symbols, and toact on the symbol even if the person who planted it is nolonger present. It is both the arbitrariness of such symbolsand their freedom from time and space constraints thatdistinguish our symbolic behavior from that of animalsand constitute the foundations ofhuman language.Theory of mind: The ability to recognize oneself as aseparate intelligence but at the same time to read the emo-tions and thoughts of others (empathy). Apes and evendomestic carnivores possess this to a degree, but onlymodern humans can respond to humanity in individualsthey will never meet.The Early Record: 2.6 - 0.6 mya
If all these are key human abilities, when did they first ap-pear? It is difficult to say, not only because the record issparse and patchy, but because the capability may or maynot be expressed for hundreds or thousands of years afterit appears and may depend on the development of otherfactors or historical events. The capability for inventing com-puters may have existed in the late Pleistocene, but couldnot be expressed without the appropriate cultural and tech-nological milieu. The limited evidence for these character-istics' early expression suggests, however, that the total pack-age was not assembled over a short period.
Problem-solving and technologicalinnovation. The first stonetools date to 2.6 mya from Ethiopia, slightly later in Kenya.There is little evidence for abstract thinking in these arti-facts as they consist of simple flakes directly related to theform of the raw material, although the ability to chooseappropriate raw materials and to derive multiple flakes from
a single block is far beyond what even the smartest apescan be taught to do. The rate of change or innovation isinitially very slow; new forms such as bifacially workedsymmetrical handaxes appear only after the first 900,000years; and tools remain static for more than 1 mya afterthat. Nevertheless, such tools made it possible for earlyhumans to shift from the largely frugivorous diet of thegreat apes to a diet with substantial carnivory and exploita-tion of new foods such as underground tubers. By 1.9-1.6mya, our early ancestors also could expand into the NearEast, Indonesia, and China, far beyond their original rangeand adapt to the new environments and faunas there. Tech-nology also seems to have made possible a shift in foodpreparation from teeth to tools, so that teeth became smallerwhile body size increased. Early human diets were prob-ably omnivorous, with meat obtained largely by scaveng-ing. Fire was controlled by 0.8 mya or earlier, facilitating anew diet, the use of caves, hunting, new technologies, andsocial time at night.There is no evidence from this time for imaginedcommu-
nities or symbolic thinking. Stone and other materials appearto have largely derived from within about 15 miles (25km) of the site. Technologies are very similar from Indiato England and from France to South Africa.Empathy, which appears very early in modern childrenbefore competent speech, may already be reflected in avery early human skull from Dmanisi in the Caucasus at1 .9 mya. The individual had lost almost all his teeth a consid-erable time before death, a condition rarely found in wildprimates. Survival of this toothless individual required ei-ther a new, very soft diet or the assistance of others.The early appearance of these features does not meanthey were as fully expressed as in modern humans or eventhat the full capacity existed as in ourselves. But it doesindicate that the human capacities do not arise suddenly infull-blown form but rather develop over time from lesshuman antecedents.Late Archaic Humans and Neanderthals:600 kya to 40 kyaBeginning before 600 kya (thousands of years ago), mostfossils in Africa, Europe, and the Near East present essen-tially modern brain sizes, although their teeth and faces are
still large. In Africa, this shift may coincide with a new stonetechnology (Levallois), requiring a greater degree of ab-
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stract thought to imagine the flakes whose shapes werepredetermined by the shaping of the cores. Evidence ofan increase in technological innovation, larger social net-works or symbolic behavior, however, is minimal until ca.400 leva, although new evidence ofan occupation of south-ern England ca. 700 kya years ago suggests the ability tomeet the challenges of a much more temperate environ-ment. Ocher's increased use in Africa by 240 kya or earliermay suggest body painting or alternatively a more utilitar-ian function. Wooden spears or javelins from Germanyand numerous remains of large animals imply a more com-plex hunting technology, which may have facilitated theoccupation of much higher temperate latitudes.Neanderthals, who occupied Eurasia as far east asUzbekistan between ca. 250 and ca. 35 kya (or even later ina few 'refuge' areas) were significantly more like modernhumans in their behavior than their predecessors. Theyburied their dead, but without clear evidence of gravegoods or associated symbols, used black and red mineralpigments found as powder, lumps and "crayons," madestone-tipped spears, and were competent hunters of largegame. Their fossil remains bear traces of both interper-sonal aggression, in the form of a knife wound, and em-pathy, as elderly and handicapped individuals survived formuch longer periods than previously. Although Neander-thals occupied Europe for at least 200 kya, their technol-ogy shows very little innovation or regional differentiationuntil the last 15 to 20,000 years of this time. The Neander-thal brain was similar in size to ours when adjusted fortheir larger body mass, but the relationship of the tongueand soft palate to the laryngeal space suggest that they may
still not have been capable of all the complex speech soundsmade by modern humans. Personal ornaments are onlyfound at the most recent Neanderthal sites, after 50 kya,dating to a time when anatomically modern humans werealready on the periphery of Europe. Does this mean theNeanderthals possessed a capacity for innovation and sym-bolic behavior, or only a facility for imitation?Modern Humans, Homo sapiens:An African OriginInto the 1 970s itwas thought that modern humans evolvedin Europe. But with the advent of new fossils and betterdating techniques, it has become clear that the oldest ana-tomically 'Homo sapiens'fossils were African. The oldest fossil
These 30,000-year-old shells from Cro-Magnon, France,represent some of the earliest evidence of humans wearingjewelry. Some shells have traces of ocher, a clue they werecolored with pigment. Photo courtesy Human OriginsProgram.
attributed to Homo sapiens in Africa is more than five timesas old as the oldest Homo sapiens in Europe. At the sametime, genetic studies demonstrate that all living humans sharea 'recent' African common ancestor who lived between100 and 200 kya. One group of African genetic lineagesshares a common ancestor with all non-Africans that isconsiderably younger, perhaps 40-80,000 years ago. Al-though at first these results were disputed, repeated geneticanalyses have confirmed our African origin. DNA sequenceshave been recovered from Neanderthals who lived as farapart as Spain and Siberia. The resulting sequences sharesimilarities with one another but indicate at least three re-gional populations and contain many sequences not sharedwith living humans, suggesting at least 400 kya of separateevolution.The rapid appearance of modern-looking people inEurope was not a punctuated "human revolution" or "greatleap forward." It was an invasion of people with longtropical limb proportions. Asia has a more complicatedbut equally punctuated history, also suggesting invasion andultimate dominance by outsiders. Indeed the first "out-of-Africa" migrations ofHomo sapiensv/ere, to the Near East,with modern humans appearing first at Skhul and Qafzehin Israel between ca. 110 and 90 kya, an initial wave thatdoes not appear to have spread beyond this region until50-60 kya. Modern humans then disappear from the Le-vant, as Levantine fossils from 90-50 kya are all Neander-thals. Modern humans expand again at or before ca. 50kya.
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II
'*?l?
1 i
"Rapid appearance of modern-looking people in Europe wasnot a great leap forward."
Modern Humans: Revolution or GradualEvolution?The earliest Homo sapiens in Europe and Asia, ca. 40kya and later, were almost certainly capable of the samerange of behaviors as we are, as indicated by their cavepaintings, sculptures, musical instruments, beads and otherjewelry, trade networks, technological innovations, regionaldiversity, economic flexibility, and ability to colonize theentire globe. There is considerable debate about earlierhumans in Africa who were physically similar to us in manyways. Some scholars argue that they were physically mod-ern but behaviorally primitive. To these scholars, modernbehavior came about suddenly, a "Human Revolution" tiedto a rapidly spreading genetic mutation for language.In a 2000 paper, Sally McBrearty and I argued other-wise, that the capabilities for these behaviors began to beexpressed and therefore existed even before modern physicalappearance, with a gradual assembly of the kinds of be-haviors we see later. This assembly was not unilineal butgeographically and temporally sport}7, with many reversals.Archaeologists look especially for technological in-novation and complexity as proxies for problem solving;for long-distance exchange and economic intensification asproxies for both planning depth and imagined communi-
ties; for regional styles that change over time as proxies forsymbolic thinking and/or imagined communities; and forbeads, images, and notational pieces along with burial ofthe dead as proxies for abstract and symbolic thinking andtheory of mind. For all of these material expressions ofbehavioral capabilities, there are modern, even living groupswithout them. While demonstrably capable of producingsuch items, these groups clearly lack the impetus or thehistory to do so, so absence may not be a good marker ofnon-modernity. But absence of all of these over long ar-chaeological stretches of time cannot be characterized as
"modern behavior."Since 2000, the rapidly accumulating record of hu-man behavioral evolution in Africa has confirmed, ratherthan contradicted, our basic model ofan earlier and moregradual accumulation of complex behaviors expressed inmaterial culture. Beads, decorated ocher and ostrich egg-
shell, innovative technologies involving hafted projectiles,and even the possibility of complex projectile weaponssystems, have all been argued for Middle Stone Age (MSA)peoples predating 60 kya. Furthermore, new dating andstudy of previously excavated materials have shown thatburials of H. sapiens with grave goods are found both inSouth Africa and in the Near East, dating to 66-90 kya and90-100 kya, respectively. These burials suggest that sym-bolic behavior characterized at least some of the earlymembers of our species long before the main "Out ofAfrica" event suggested by genetic dating.But after more than a million years with little change intechnology, the African record suggests that well beforethe first appearance ofHomo sapiens, even before 285 kya,behavior had begun to change. New technologies producedstandardized stone flakes and long thin blades, ocher pro-cessing increased, and many sites have small quantities
?
up to 5%?of stone material derived from sources a con-siderable distance away, as much as 125 miles (200 or morekm)? the first sign of an expanded social network. Thebehavioral changes reflected in these finds are not suddenor directional. The evidence for them is interspersed with
sites containing the old symmetrical large cutting tools, orsimple flake technologies, or lacking evidence for ocher orexotic stone. But the general trend is towards more com-plex behaviors with time. Importantly, by ca. 267 kya, sev-eral sites in South and East Africa include carefully madestone points, designed for hafting onto spear shafts.
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New TechnologiesMore dramatic changes in behavior occur after the ap-pearance of Homo sapiens. From South Africa to Egyptand from the western Sahara to Ethiopia, evidence forcomplex technologies and new tools increases especiallyafter 100 kya. In Ethiopia, the first Homo sapiens at about195 kya are associated with advanced flake technologiesbut the older symmetrical large cutting tools continue atsome sites in the Horn of Africa. Before 90 kya, stonepoints are large or thick, and were likely hafted onto thrust-ing spears used in close encounters with prey. But after 90kya, the points become tiny and light. Possibly these verysmall later points, which could not have delivered a lethalblow to a large animal, were hafted on the ends of spearthrower darts or arrows, and even associated with the useof poison.As earlv as 130 kya, another set of technological inno-vations appears to have focused on fishing. In the easternDemocratic Republic of Congo (Zaire) our team discov-ered a series of what appeared to be Middle Stone Agelocalities along the river. Excavations at three sites revealedmammalian fauna and lithic artifacts but also a series ofbarbed bone points associated with thousands of fishbones. The dates for these sites have varied, but lumines-cence dating suggests an age of 80-90 kya, and there is noevidence for an age less than 60 kya. Again, this is a com-plex technology that appears to have been outside Nean-derthal competency.Small projectile armatures in a complex weapons sys-tem could have given the edge to later modern humans,allowing populations to expand both within and outsideAfrica at the expense of the Neanderthals and other ar-chaic populations. Neanderthals had many injuries frompersonal encounters with large dangerous animals, but latermoderns had very few. Neanderthals also had many moresigns of dietary stress in their bones and teeth than the earlymoderns who succeeded them.Long-Distance ExchangeAt several sites in East and Central Africa, some stone toolsmade by early modern humans use stone that does notcome from the local area. Throughout East Africa there isa preference in many sites for obsidian, a fine black volca-nic glass with very specific chemical characteristics. In manyareas, such as the Aduma area in the Mddle Awash region
of Ethiopia, obsidian sources do not occur in the immedi-ate vicinity of the sites, and the obsidians themselves arevaried and appear to derive from multiple sources. Whenthe chemistry of the obsidian can be matched to specificsources, as at Mumba in Tanzania, it suggests that obsidianwas being moved more than 125 miles (200 km) in somecases. This suggests the existence of trading networks, or
"imagined communities." Distant trading networks wouldbenefit from the use of symbols to identify members ofsuch a community, so it is not surprising that ocher andother minerals were also processed for pigment at some
sites such as Twin Rivers in Zambia, as early as 240 kya.Other indicators ofimagined communities are the regional
"styles" of projectile points that possibly identify social
entities in space.Symbolic BehaviorSo far, we have demonstrated the presence of technologi-cal innovation, economic intensification, long distance ex-change, and regional styles in the behavioral repertoire ofearly modern humans. But is there hard evidence for sym-bolic behavior? In 2002, an extraordinary piece ofengravedocher was described from Blombos cave in South Africa.It and a second similar piece clearly suggest that ocher hadmore than a utilitarian function. Many other pieces ofocher,bone, and eggshell with engraved geometric or linear de-signs are known both from this site and from other south-ern African sites, including fragments of decorated ostricheggshell containers from ca. 65 kya at the Atlantic coastal
site of Diepkloof.Beads and other body ornaments are unequivocal evi-dence for symbolic behavior and for fully human status, asthey have little utilitarian function. In traditional huntingsocieties, beads provide the basis of exchange networksthat served to tie distant people together in a mutual sup-port network, particularly useful when times are bad. Indi-viduals deliberately build these networks up as they growinto middle age and acquire major responsibilities for rais-ing and marrying off children or for supporting elderlyparents. As they age and their needs decrease, individualsbegin to reduce the size of these networks.Beads and personal ornaments such as rings or head-pieces also serve as markers of social identity or statusworldwide. Examples include wedding bands, the color-ful collars of the Maasai, and diamond necklaces of soci-
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ety women (or men). Despite extensive excavation, nobeads are known from Europe before ca. 50 kya. EarlyAfrican sites have yielded a few ostrich eggshell beads inearly sites?an unfinished one from South Africa(Boomplaas) dated to ca. 60-80 kya, and several from Tan-zania (Mumba) dated direcdy to between 45 and 52 kya.In 2004, a series of perforated shell beads from the coastof South Africa, dated to 76 kya, made headlines as theoldest evidence for personal ornaments. Even older shellbeads have been described from sites in North and EastAfrica, as well as in sites of early modern humans in theNear East.The evidence for human burial practices with graveofferings indicative of symbolic behavior within Africa islimited, due in part to the relative dominance of open airexcavations where bone preservation is poor, and in partto probable cultural practices of burial away from living
sites. Two relatively elaborate cave burials at early dates,however, confirm the antiquity of this practice among mod-ern humans at opposite ends of their early geographicrange: an elaborate modern human burial at Qafzeh inIsrael dated to 100-130 kya, a time when both modernhumans and African faunas expanded into the Levant andthe burial of a child at Border Cave in South Africa datedto 66-90 kya. The child burial is associated with what ap-pears to be ocher and has a large perforated Conns shell inits chest area. The nearest source for the shell is the IndianOcean ca. 50 miles or 80 km away. The Qafzeh individualwas associated with 71 pieces of red ocher, and also witha perforated bivalve shell. These two sites constitute theearliest clear evidence for symbolic burial with grave goodsand red ocher, practices that suggest a belief in the survivalof a spirit after death.Emergence of Humanness: A Gradual ProcessThe accelerating rate of technological innovation was astepwise process, not a sudden event related to language.By 70 to 60 kya, well before the out-of-Africa event thatled to Neanderthal extinction, anatomically modern hu-mans in Africa, and occasionally in the Levant, had lightcomplex projectile weaponry, fishing and bone fishingspears, long distance exchange networks, ocher, deliberateburial with grave goods, regionally distinctive point styles,symbolic engravings and personal ornaments. Within Af-
rica, there was probably a complex web of inter-regionalmigration and local extinction that makes the record patchy
and discontinuous. In addition, demographic and climaticfactors may affect the degree to which any of these mod-ern human capabilities are expressed. Ethnographic stud-ies suggest, for example, that symbolic expression, subsis-tence practices, and regional networks intensify under con-dition of resource stress.Neanderthals, on the other hand, before 50 kya, hadhafted spear points, used a large amount of black coloringmaterials, and practiced simple burials without offeringsor ocher. There is little evidence in this early time range forNeanderthal fishing and none for bone tools, musical in-struments, cave art, or personal ornaments. After 40-50kya, when modern humans were already on the Neander-thals' periphery or perhaps in their midst, Neanderthalsdeveloped or adopted some of the same traits?particu-larly the beads and stone technologies. But they still lackedsmall light projectile armatures (points) and rarely if everwent fishing. And the really long distance raw materials areonly marginally present towards the end of their existenceat the northeast edge of their range in Eastern Europe andCentral Asia. In both regions we would expect human ter-
ritories to be very large and populations sparse.Why was Howo sapiens able to replace Neanderthals inEurasia after 50 kya but not before? There seem to bethree possibilities: 1) a sudden genetic mutation, 2) techno-logical superiority, or 3) more sophisticated social networks.These networks, supported by a greater use of symbols oreven language, would have buffered humans against risks.A fourth hypothesis is that invading Africans brought withthem epidemic diseases to which the Neanderthals had no
resistance.In any event, Neanderthals survived long enough toleave archaeological and/or fossil traces in several sites insouthern Europe that are contemporary with sites of earlymodern humans in Europe over a period of at least 6000-7000 years. Co-existence in the Near East may have oc-curred over an even longer period. New work on the nuclearDNA genome of Neanderthals even suggests that mod-ern populations in Eurasia (but not in Africa) carry a smallpercentage (1-4%) of Neanderthal genes, implying thatNeanderthals and modern humans interbred in the NearEast, before modern humans expanded to the rest ofEurasia. (This and other new genetic studies bearing onhuman evolution and migration will be covered in a futureAnthroNotes article)
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^"hile the answer to the question ofwhy Homo sapienswas able to replace Neanderthals is almost certainly morecomplicated than any of these three simple hypotheses of-fered above, and may involve combinations of them andothers, the evidence against a revolutionary genetic event isstrongwhen you consider Africa. That continent is charac-terized by the earlier appearance oftechnological and eco-nomic complexity, as well as of complex symbolic behav-ior. The patterning of change both during and at the endof the Middle Stone Age period of early Homo sapiens isalso very different from that consistent with a genetic revo-lution, as it is both spotty and gradual. Such gradual pat-terning is much better explained in earlier anatomicallymodern humans bv assuming the existence in earlier ana-tomically modern humans ofmodern behavioral capabili-ties that are variably expressed when conditions call forthem. NXTien either climate change or population growthcreated effective crowding, in an otherwise sparsely inhab-ited landscape, such pre-adaptation could have becomeexpressed in modern behavioral capabilities.ConclusionCurrently available data suggest that our ancestors pos-sessed some basic capacities for technological innovationand symbolic behavior before the line leading to Neander-thals in Europe diverged from the line leading to Ana-tomically Modern Humans (AMH) in Africa, a split whichgenetics and archaeology concur in dating to between 400and 800 kya. These more human capacities became moreelaborately expressed earlier in Africa because of its largerpopulation, more diversified landscape, and greater po-tential for interregional interaction. As a result, by 60 kya,AMH entering Eurasia were able to expand and replaceNeanderthals, who responded initially with increased ex-pression of some of these capabilities on their own, butwere ultimately unable to prevail. In the future, new datafrom the fossil and archaeological records but also fromthe evolutionary history ofthe brain, its faculties, and genesthat affect behavior may shed further light on the questionofwhat it means to be human.
Alison Brooks at Olorgesailie, Kenya.
ReferencesAmbrose, S. 2001. "Paleolithic Technology and HumanEvolution." Science 299 (5509): 1748-53.Anton, S.C., and C.C. Swisher III. 2004. "Early Dispersalsof Homo from Africa." Annual Review of Anthropology 33:271-96.Barham, L.S. 1998. "Possible Early Pigment Use in South-Central Africa." CurrentAnthropology'39: 703-20.Bouzouggar, A., etal. 2007. "82,000-Year-Old Shell Beadsfrom North Africa and Implications for the Origin ofModern Human Behavior." Proceedings of the NationalAcad-emy ofSciences 104: 9964-69.Brooks, A.S. 2010. "What is a Human? AnthropologicalPerspectives on the Origins of Humanness." In M. Jeeves,
ed., RethinkingHuman Nature. Eerdmans. In press.
(continued on next page)
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Brooks, A.S., eta/. 2006. "Projectile Technologies of theAfrican MSA: Implications for Modern Human Origins."In E. Hovers and S. Kuhn eds., Transitions before the Transi-tion: Evolution and Stability in the Middle Paleolithic andMiddleStoneAge, pp. 233-55. Kluwer Academics/Plenum.Green, R.E. etal. 2010. 'A draft sequence of the Neandertalgenome." Science'328: 710-722.Henshilwood, C.S., etal. 2004. "Mddle Stone Age beadsfrom South Africa." Science 304: 404. (See supporting onlinematerial for pictures). See also Journal of Human Evolution48, no. 1 (2005): 3-25.Henshilwood, C.S,et al. 2002. "Emergence of ModernHuman Behavior: Engravings from South Africa." Science295: 1278-80.Lieberman, P., and R. C. McCarthy. 2007. "Tracking theevolution of language and speech: Comparing vocal tractsto identify speech capabilities." Expedition 49 (2): 1 5-20.Lordkipanize D, etal. 2005. "Anthropology: The EarliestToothless Hominin Skull." Nature 434: 717-18.Marean C.W., et al 2007. "Early Human Use of MarineResources and Pigment in South Africa during the MddlePleistocene." Nature 449: 905-08.McBrearty, S., and A. Brooks. 2000. "The Revolution ThatWasn't: A New Interpretation of the Origin of ModernHuman Behavior." Journal of Human Evolution 39: 453-563.McDougall, L, F. H. Brown, and J. G. Fleagle. 2005. "Strati-graphic Placement and Age of Modern Humans fromKibish, Ethiopia." Nature 433: 733-36.Mercader, Julio, etal. 2007. "4,300-Year-Old ChimpanzeeSites and the Origins of Percussive Stone Technology."Proceedings of'the National'Academy ofSciences 104 (9): 3043-48.Pearson, Osbjorn M. 2001 . Postcranial Remains and Mod-ern Human Origins. EvolutionaryAnthropology 9 (6): 229-47.
Pettitt, Paul A. 2001. "The Neanderthal Dead: ExploringMortuary Variability in Mddle Paleolithic Eurasia." BeforeFarming 1: 1-19.
Potts, Richard and Christopher Sloan. 2010. What does itMean to be Human?National Geographic.
Roche, H.A., etal. 1999. "Early Hominid Stone Tool Pro-duction and Technical Skill 2.34 Mya in West Turkana,Kenya. Nature 399: 57-60.Semaw, S., M. etal. 2003. "2.6 Million-Year-Old Stone Toolsand Associated Bones from OGS-6 and OGS-7, Gona,Afar, Ethiopia." Journal of Human Evolution 45:
1
69-11
.
Sherwood, C. C, E Subiaul, and T Zawidzki. 2008. "ANatural History of the Human Mnd: Tracing Evolution-ary Changes in Brain and Cognition." Journal of Anatomy212 (4): 426-54.Vanhaeren, M., etal. 2006. "Mddle Paleolithic Shell Beadsin Israel and Algeria." Science 312: 1785-88.
For a more complete list of references, emailanthroutreach@si.edu.
Alison S. Brooks is Professor of Anthropology at GeorgeWashington University and Editor of 'AnthroNotes."
Australopithecus afarensis. Starting with a cast skull, artistJohn Gurche builds layers of muscle, fat, and skin to createhyper-realistic busts of human ancestors featured in thenew David H. Koch Hall ofHuman Origins at theSmithsonian's National Museum of Natural History.
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PRESENTING HUMANEVOLUTION TO THE PUBLIC:THE SMITHSONIAN'S HALL OFHUMAN ORIGINSby Rick PottsAt twelve o'clock noon, on March 17, 1910, theSmithsonian's newly built National Museum ofNatural History opened its doors to the public forthe first time. Exacdv one hundred years later the museumchose to celebrate this auspicious occasion with the open-ing of the long-awaited exhibition, The DavidH. Koch Hallof Human Origins. This major exhibition opened at exactlynoon on March 17, 2010 to hundreds of visitors eager tosee the widely publicized human origins hall.The exhibition presents nearly 300 objects, includingoriginal fossils and artifacts, along with exact replicas offragile and unique specimens that must be kept and pro-tected in the countries where they were found. The mainpurpose of the Hall ofHuman Origins is to show the evi-dence of humanity's evolution over time; how the devel-opment of human features helps us understand who weare as a species today; and why knowing about this pro-cess is important. Not just based on Smithsonian research,the exhibit is an international effort built on Smithsonianpartnerships with more than 60 research institutions andmore than 100 scientists and educators from around thewrorld.
What Does It Mean To Be Human?The exhibition and its companion website offers the pub-lic an opportunity to explore the scientific finds that shedlight on one of the significant sparks to human curiosity?our own origins. The primary theme of the exhibition isnot an answer, but rather a question: What Does itMean to beHuman?This central question goes to the heart ofhumancuriosity: who are we as human beings, how did we get here,and where are we going? By choosing a question for ourexhibition theme, the goal is to invite each museum visitorto explore the scientific discoveries about human originsand to connect their lives and personal perspectives to theevidence of how our species evolved.In the central area of the L-shaped exhibition, visitors areinvited to type in their answers to this central question Whatdoes it mean to be human?' Their responses, which areposted on our web site, www.HumanOrigins. si.edu . helpinform us of the immense diversity of thoughts our mu-seum and web visitors have as they encounter the evidenceof human evolution. Answers to this question are informedby many perspectives drawn from philosophy, religion, the
arts, the sciences, and every-day life experiences.The Story Unfolds
Fossils and archeological finds highlighted both in the exhi-bition and website reflect, for example, the roots ofwalk-ing upright, transitions in technology, enlargement of thebrain, changes in the face and the body, and the diversityof species that are part of our evolutionary tree as re-flected in our biological ancestors and nearest relatives that
Exhibit hallphotos,courtesyChip Clarkand HumanOriginsProgram.
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science has so far uncovered. The hall's interactive displaystake our visitors back through time to see how these earlypredecessors lived, the survival challenges they faced, andthe elements of humanness they had accumulated at cer-tain points in time.Every fossil has a story to tell because each one wasonce part of a living, breathing individual whose specieshad evolved some combination of the features that definehuman beings today. As a baseline, each of these specieswalked upright and had small eye teeth (canine teeth).Bipedality and small canines define all members of ourfamily tree back to at least 6 million years ago. The earliestof these species walked upright and had long, powerfularms?a union of features that persisted for about 4 mil-lion years and enabled these oldest ancestors and evolu-tionary cousins to walk on the ground and climb trees tofind food and safety.Later species abandoned their expertise in the trees asthey developed stone toolmaking skills and somewhat en-larged brains. Still later species, like Homo heidelbergensis, werethe first we know of to build hearths and shelters, and tohunt using wooden spears. Later in time, the Neanderthals{Homo neandeiihalensis) were very clever at making tools andusing local food and stone resources; they even buried theirdead on occasion and created symbolic artifacts of un-known meaning to us today. However, all of these species,includingmam side branches, are no longer around; theirways of life now extinct, they leave our own species, Homo
sapiens, as the last survivor of a once diverse evolutionarytree.
In 1910, the scientific record of human origins con-sisted of a few dozen fossils, mostly the bones ofthe famedNeanderthals of Europe. Nearly all of the fossils, archeo-logical remains, and genetic findings that a natural historymuseum can offer on this subject have been found overthe past century. Now, in 2010, the science of human ori-gins is informed by more than 6,000 fossil individuals, rang-ing from isolated teeth to well-preserved skeletons, spreadout over the past 6 million years. These fossils along withhundreds of thousands of archeological remains, whichecho the ways of life of early human species, offer a re-markable record of the accumulation of features that makethe human species unique.Milestones in Becoming HumanHumans evolved over millions of years in response to achanging world. The 6 million years of human evolutionhave comprised one of the most dramatic eras of envi-ronmental change in Earth's history, with large swings be-tween warm and cold, and between wet and dry. The HallofHuman Origins is the first exhibition on human evolutionto explore the drama of climate change and the survivalchallenges it presented to our early ancestors. These chal-lenges set the stage for the changes ? the adaptations ? thatevolved over time.The exhibition is organized around a series of displaysthat present the key milestones in human evolution. In onearea, adults and children alike enjoy stepping in an exactreproduction of the oldest known bipedal footprints, 3.6million years old, made by the species Australopithecus afarensis
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(the most famous fossil ofwhich is known as Lucy). An-other area shows that, by about 2 million years ago, ourancestors began to delay eating their food, carrying it toplaces where meat could be butchered and bones withnutritious marrow could be smashed open. Later in time,between 800,000 and 400,000 years ago, there is ampleevidence of hearths where food was cooked and of well-made shelters indicating that our ancestors made camp-
sites. Still later, by about 130,000 years ago, early groups ofour own species exchanged stone materials across vast dis-tances ofmore than 100 km. This evidence shows the be-ginning of social networks that stretched across those an-cient landscapes. They didn't have Twitter or Facebook,that's for sure?but thev kept track of one another from
afar, and they knew who had what to offer!The exhibition is filled with intriguing highlights alongthe milestone trail. The fastest pace of brain enlargementbegan around 800,000 years ago, and led to the evolutionby about 200,000 years ago of the two largest-brainedspecies, the Neanderthals and ourselves. By this time, chil-dren took a long time to grow up, since large brains takemany years to mature. Adults were faced with significantdemands to find nutritious food to feed the brain of eachchild as he or she grew. Challenges, of course, still echoprominently in our lives today and can be traced to theevolution of the big human brain over hundreds of thou-sands of years and the prolonged growth of the brain inevery living person.
The exhibition also explores the oldest stone technolo-gies, which remained largely unchanged for more than amillion years. The exhibition shows how the long-livedhandaxe tradition eventually gave way to smaller and moreinnovative technologies: for example, projectile points by100,000 years ago, used to catch fast and dangerous prey;and sewing needles by about 25,000 years ago, enablingearly members of our species to make snug- fitting cloth-ing. Clothing made the difference between life and deathas populations moved into ice-age habitats.Among the most interesting of human capabilities isour use of symbolic language. The oldest clues concerningcomplex symbols are pieces of pigment?faceted sticksand lumps of ocher (yellowish, redish, brownish in color)and limonite (yellowish-brown color), essentially the world'soldest crayons, dated to 250,000 years old. The use ofcolor to mark objects, or perhaps even the body to createa sense of personal or group identity, is the best evidencewe have for when language, the most complex of oursymbolic abilities, first emerged.As visitors explore the Hall and website, there are ampleopportunities to learn about our own species, Homo sapiens,which evolved around 200,000 years ago. By about 17,000years ago, all species of early humans except our own hadbecome extinct. Despite our prevalence today, even ourspecies had its endangered moments. Between 90,000 and70,000 years ago, as African environments oscillated be-tween drought and moist times, the population that gave
rise to almost all of the genetic diversity among the world's
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peoples today had dwindled dramatically to somewherebetween 10,000 and 600 reproducing adults. We almostbecame extinct. However, by that time, Homo sapiens haddeveloped a certain resilience in the face of millions ofyears of survival challenges.By about 12,000 years ago, pockets of people in sev-
eral regions began domesticating some plants and animals.These activities ultimately gave rise to the agriculture onwhich modern societies depend. The exhibition providesan opportunity to contemplate the enormous pace ofpopulation growth since that time, our deep influence onthe planet, and how our species became a turning point inthe history of life. Among the Hall's many interactive dis-plays, one of the most intriguing is a game called 'KeepYour Species Alive,' in which the players imagine the sig-nificance of key decisions for the future.ReflectionsAs the curator of the HallofHuman Origins, I began todevelop an environmental approach to the exhibition soonafter arriving at the Smithsonian in 1 985. Twenty-five yearsago, it was a difficult decision to leave Yale University, where
I was a young assistant professor, working in a setting withgreat potential for developing my research career. Eventu-
ally, I saw the move to the U.S. National Museum as aspecial opportunity not only to lead digs and expeditionsbut also to make sure that the profound questions of hu-man origins and the scientific finds that illuminate thesequestions would not be confined to a university classroom.My transition to the Smithsonian meant an opportunity tobring research discoveries on human evolution to the wid-est public audience.
It did not happen all at once, though. In fact, it tooknearly 20 years to assemble the best combination ofpeople.John Gurche, to name just one early member ofour team,is the foremost artist-anatomist in the lifelike reconstruc-tion of early human species. John is responsible for theastonishing reconstructions of the heads and statues ofseveral early human species that are featured in the Hall.The 20 years also gave me time to explore new scien-tific avenues, which ultimately shaped the exhibition. Afterseveral years of digging in the Great Rift Valley of south-ern Kenya, at the stone handaxe site of Olorgesailie, I real-ized that what I thought we knew about the ancient settingofhuman evolution?long assumed to have been the Af-rican savanna grassland?was by no means a single, con-sistent environment. The geological clues indicated, instead,that the climate kept changing.As I delved into the environmental sciences, the more
I realized that rather than any one environment or trend,the continual shifting of the landscapes where early hu-mans lived characterized the period of human evolution.This was a story worth telling?and a huge area of scien-tific investigation that had not yet been presented in a pub-lic exhibition.By 2005, it became one of the museum's top prioritiesto present this environmental theme along with the vastnumber of fossils found over the previous two decades.Byjanuary 2007, our exhibition core team began to meet,and a three-year period for developing the entire Hall wasplaced on a fast track to develop all its interactive displays,the many objects for people to see, and the state-of-the-artreconstructions of our early ancestors.
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Back to the BeginningOn the evening of March 17, the Smithsonian hosted agala dinner to commemorate the opening of the Hall ofHuman Origins and our museum's Centennial. The dinnerhonored Mr. David Koch and Dr. Peter Buck, theexhibition's two principal benefactors. Meave and RichardLeakey among other notable scientists attended, as didmembers of Congress, the Smithsonian leadership, keymembers of our exhibition team, and many other fasci-nating people.
I had dreamed of this exhibit off and on for 25 yearsand then almost miraculously I had the opportunity to workon it nearly even* day with incredibly talented exhibit de-signers, writers, tech experts, educators, and fellow scien-tists. I had not thought much about the final day actuallyarriving. Still, as the long-awaited day unfolded, I couldnot help think that it was passing way too quickly!In many conversations that evening, I kept mentioningthe exhibition tours we were to give in the coming days,the lecture series that would start in a couple ofweeks, andthe network of educators and scientists eager to help bringthe exhibition's ideas and messages to the American andinternational public. Gradually, it dawned on me that theopening of the Hall was not the end of the road, but thestart of an ongoing endeavor of great responsibility.
I am eager to return to the field and continue our digsin Kenya, China, and other countries. But now there is moreto it than that. Our Smithsonian team can hardly wait fornew- discoveries by researchers all over the world that willmake the updates to our exhibition, additions to our newwebsite, and our educational events for the public excitingpossibilities for the future. As with science itself, where eachnew significant discovery leads to new ideas and explora-tions, I now- see that our efforts to present the science ofhuman origins to the public will lead to new ways ofmak-ing the science as exciting and as relevant to as many peopleas possible.The opening of the exhibition has become in retrospectthe signal of a terrific beginning. If there is any answer theexhibition gives to the question "What does it mean to behuman?' it is that "being human' has been, in part, a matter
Rick Potts in his Smithsonian office.
of 'becoming human'?a wondrous process of changeover time, an ancestry that connects all people to one an-other and our species to every form of life on planet Earth.Every day this hall and its rich website will continue to helppeople explore and learn about this amazing scientific quest.
For further information about the exhibit and theSmithsonian's Human Origins Program, consult its com-panion publication and website:
Potts, Richard and Christopher Sloan. 2010. What Does ItMean to be Human'? National Geographic.Human Origins Website: http://humanorigins.si.edu/
Rick Potts is Director, Human Origins Program, and Curator,
"The DavidH Koch Hall ofHuman Origins. "
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TEACHERS CORNER:RESOURCES FROM THE SIHUMAN ORIGINS PROGRAMby Briana Pobiner
In the previous article, Curator Rick Potts discussed thenew David H. Koch Hall of Human Origins. He notedthat, not unlike scientific inquiry itself, the exhibition'stheme is a question rather than an answer: What does itmean
to be hnman?This theme is even more prevalent on the newweb site, www.HumanC )rigins.si.edu . On this site, we havethe opportunity to share the wealth of evidence for, andcurrent research about, human evolution with millions ofpeople from around the world. While the website was cre-ated with diverse audiences in mind, one of the primaryaudiences is teachers. This Teachers Corner summarizes theresources currently on the human origins website of inter-
est to teachers and other educators. The website is designedto be easily expandable as we continue to add new contentand features. We welcome feedback on the website; pleaseemail your suggestions and comments toHumanC )ngins(a;si.eduHUMAN ORIGINS WEBSITE:
EducationA variety of teacher and educator-specific resources areassembled in the Education section of the web site: http://humanorigins.si.edu/education . These include:
1) A downloadable, PDF 'Educators Guide" to theexhibition hall, specifically designed for class fieldtrips. In lieu of offering tours for school groups,the Educators Guide is designed with pre-, dur-ing, and post-visit activities for students in grades5-12. There are data collection sheets for studentsto fill out during a visit and hot links within the
PDF connecting to other areas of the website.These sections correct common misconceptionsabout human evolution and offer further readings(books and websites).
2) Links to lesson plans on human evolution for usein the classroom. Borrowed from the "Under-standing Evolution" website (University of Cali-fornia Museum of Paleontology), all these planshave been tested and vetted by teachers.
3) A private discussion forum for educators, whereteachers can discuss ways to best use the websitein the classroom, exchange ideas about teachinghuman evolution, etc.
4) Information about the HopEdNet (Human Ori-gins Program Education Network), a nascentlarge-scale, long-term effort to bring educators and
scientists together to focus on teaching and learn-ing about human origins.
5) A section for college-age students with links tosummer field schools.
6) Fun Facts? short tidbits about human evolutionthat are great ways to get students thinking aboutthe topic.ResourcesThe resources section of the web site http://humanorigins.si.edu/resources also has a variety of useful
areas:
1) A general introduction to human evolution.
2) A human evolution glossary. Definitions of termsalso are available by hovering a mouse over thoseterms anywhere on the website.
3) A section on "What's Hot in Human Origins?"keeps visitors up-to-date with the latest key dis-coveries in this dynamic field of research.
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4) Links to all the site's multimedia resources?podcasts (audio), videos, and photograph
slideshows.
5) A "How Do We Know?" section, which usesmaterial from the exhibition to outline some ex-amples of how we know what we know in thescience ofhuman origins (a great example of sci-
entific knowledge in general).FAQ (Frequently Asked Questions)Hidden in the top right corner of the website is a FAQsection http://humanorigins.si.edu/faq . which features agrowing list of Frequently Asked Questions about humanevolution?and their answers. Some examples include "Howdo scientists know the age of fossils?" "How does evolu-tion explain complex organisms like humans?" "How arehumans and monkeys related?" and "Can the concept ofevolution co-exist with religious faith?" In adding to thislist over time, we will be drawing from the Evolution FAQkiosk in the Hall of Human Origins, where visitors cantype in their questions about human evolution.Human Evolution Evidence
\X"hile many of this section's resources will likely be useful,including a lightbox feature for large format photographsof fossils and artifacts, three particular sections can be high-lighted:
1) Human Evolution Evidence is one of the most uniqueand popular features of the website with a 3D Collectionhttp://humanorigins.si.edu/evidence/3d-collection.This
collection features rotatable, 3-dimensional scans ofhun-dreds of fossils and artifacts, most ofwhich are found inthe Hall of Human Origins. One of the most useful featuresof this teaching collection is that each object is available in
a 3D PowerPoint slide. These rotatable objects can be used
as part ofyour own presentation!
"~~^^^S ?>??. Hall of Human Origins mm*
^? =1Hot in What Does It Mean '-48S&igins? To Be Human?
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2) Building on this 3D collection is our Mystery Skull In-teractive http://humanorigins.si.edu/evidence/human-fos-
sils /mystery-skull-interactive , where students become sci-
entists! A mystery skull is presented. Comparison to otherknown skulls can help determine what species it belongsto?in 3D. Hints for each mystery skull are available to helpstudents learn how to look at skulls and make compari-sons among them. (continued on next page)
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3) Also in this area of the website are detailed summariesof each early human species. (Please note that the term
"early human" is used instead of "hominin," following onthe terminology used in the exhibition.) http://humanorigins.si.edu/evidence/human-fossils/species in-cludes an audio pronunciation guide, a reconstruction ofwhat the species may have looked like, information aboutwhen and where fossils of that species have been found(and when it was first discovered), estimated height and
weight, and information about the species' unique adapta-tions. Short bibliographies are available for students writ-ing reports or papers.Human Evolution Research
This section goes into more detail about the research thatthe Human Origins Program team is undertaking. Overtime this section will feature research by some of our re-search associates and other interesting projects. Similar tothe Human Evolution Evidence section, some pages fea-ture more concise information, while others have moredetail, including bibliographies. There are also threeinteractives in this section:
1) Olorgesailie: Adventures in the Rift Valley http://humanorigins.si.edu/research/east-african-research/adven-tares-rift-valley-interactive . In this interactive, students againget to be the scientists ? this time, on a field expedition toOlorgesailie, the Smithsonian's research site in southernKenya. Students search for evidence across the landscape
at Olorgesailie to answer a variety of research questions,keeping a notebook to track their findings along the way.
2) Fossil Forensics http://humanorigins.si.edu/research / fossil-forensics-interactive . where students cansee how scientists 'read' bones for forensic-style clues.3)Timeline Interactive http://humanorigins.si.edu/re-search/climate-research/timeline-interactive . which featuresclickable links to early human species, fossils specimens,human evolution milestones, and climate change evidence,
all in the context of a timeline with a zoom feature sostudents can explore particular times in human evolutionthat they find most interesting.
Broader Social Impacts CommitteeOn the Home Page is a section called "Human Evolution:Religious Perspectives," which links to the pages about theBroader Social Impacts Committee http://humanorigins.si.edu/about/bsic . Recognmngthe challengesposed by evolution, and especially the topic ofhuman evo-lution for some people, the Human Origins Program hasassembled this committee, comprised of people from di-verse religious and philosophical communities from aroundthe United States. The committee is assisting in public com-munication and dialogue surrounding the exhibition WhatDoes ItMean To Be Human? and helping promote outreachefforts in human origins. The committee also is continuingto develop web-based resources, which teachers may finduseful in the classroom.SOCIAL MEDIA:Become a fan of the Smithsonian's Human Origins Pro-gram on Facebook http://www.facebook.com/smithy >nian.luiman<>riirins and follow us on Twitter http://twdtter.com/HumanOrigins to keep up with even moreof the latest discoveries in, and conversations about, hu-man origins research.
Briana Pobiner is Education & Outreach Specialist, Hu-man Origins Program.
[See the article, "Teaching Human Evolution: Websites," byB. Pobiner in the Fall 2008 issue of AnthroNotes, p. 14.]
PLEASE SIGN UP FOR THEELECTRONIC VERSION.HELP US REDUCE PAPERAND PRINTING COSTS.ANTHRONOTES IS GOINGGREEN! EMAILANTHROUTREACH@SI.EDU
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AnthroNotes Volume 31 No. 1 Spring 2010NEW PERSPECTIVES ON THEEVOLUTION OF BIPEDALISMby A.lison S. BrooksE^ arly scholars of natural history recognized that bi-pedalism, tool use, and language were among the^nost important defining characteristics ofour spe-
cies. In 1780, Blumenbach actually classified humans in aseparate order, the "Bimana" or two-handed animals, im-plying only two limbs used for locomotion. Even as late asthe 1950s, many thought that large brains and bipedalismhad evolved together, an impression supported by the largebrain of the "Piltdown Man" forgery. But as recent fossilevidence makes clear, bipedalism actually developed longbefore there was any sign of enlarged brains, tool-making,or any kind of symbolic behavior that would suggest lan-guage abilities.Why did our lineage adopt such an unusual way ofgetting around, a way that is exceedingly rare among mam-mals? There are other bipeds, but kangaroos move byhopping on their hind legs, balanced by a long heavy tail,and many birds such as ostriches run on the ground withbent knees, also balanced by a tail. Humans are the onlystriding, tailless bipeds. Because we started out as taillessapes, our bodies had to change in many ways to balancethe body oy^er that one leg during walking and running.Our head is balanced atop the spine rather than out in frontof it, and our spine itself is S-curved, to balance the massof the upper body over the legs. This alone causes us agreat deal of griefby putting strain on the lower back andneck. Our pelvis changed from a long linear shape withflat blades (ilia) extending up the back to a basin shape thatcradled the abdominal organs but created problems lateron in evolution for birthing a large-brained baby. The newshape of the pelvis changed the position of the musclesattached to those blades, which were used to pull the legback but now extend to the side over the hip joint to keepyou from falling over when you pick up one leg and standon the other. Otherwise (or if those muscles aren't func-tioning well) you would have to walk the way chimpan-zees and some other four-footed animals do?leaning side-ways over the leg you stand on to keep your balance and
prevent falling towards the leg you are lifting. The hipjoints are bigger than in apes of comparable body weightsince they carry our full weight whenever we are movingor standing. To make it easier to balance on one leg, ourknees are positioned directly under the body, which makesthe thigh bone (femur) slant inwards from hip to knee.Finally our foot changed from a grasping appendage to apropulsive one, with a bigger, straighter and stronger bigtoe in line with the shorter lateral toes for pushing off, andwith both a longitudinal and transverse arch to stiffen thefoot for toe-off. This literally puts a spring in our stepswhen we run.Fossil Evidence for BipedalismEven the very fragmentary fossil remains from early inhuman evolution suggest that adaptation for bipedalismwas an early and essential step, so to speak, on the road tobecoming human. At 6-7 million years ago (mya), two earlyancestors represented by the fossils Sahelanthropus tchadensisfrom Chad and Orrorin tugenensis from Kenya appear tohave already changed their way of getting around. Thehole in the base of Sahelanthropus\ skull for its spinal cordhad become reoriented so it points downward rather thanbackward, and it is positioned a little further forward sug-gesting that the head was becoming more balanced on topof a vertical upper spine. The cross-section and width ofthe femur of Orrorin suggests that it was already bearingmore weight, although the hip joint would have beensmaller than in modern humans. In addition, the long nar-row neck of the femur, which joins it to the hip socket,indicates that the pelvis (which is missing) was already muchbroader than in apes. The curved toe and finger bones andthe muscle markings and shape of the upper arm bonesuggest that Orrorin also spent a lot of time climbing aroundin trees, to sleep, eat, or escape from predators.An almost complete skeleton of Krdipithecus ramidusfrom Ethiopia, dating to 4.4 mya and published in Octo-ber 2009, has an even more curious combination of traits.The upper blades of the pelvis (ilia) are shorter and broaderthan in apes, and the pelvis as a whole apparently has abasin shape, suggesting a degree of adaptation for uprightwalking. But the foot retains a fully opposable big toe forgrasping and climbing in trees, and it does not have eithera longitudinal or a transverse arch.
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From 4.4 to ca. 1.9 mya, members of the genusAustralopithecus, whose most complete skeletons so far areLucy and the recently reported skeletons ofAustralopithecus
sediba {Science 4/9/201 0), were more committed to habitualbipedal walking, with an S-curved spine, a very wide ba-sin-shaped pelvis, an inward-slanting femur, a large big toeclose to the other shorter toes, an expanded heel, and somedegree of arch in the foot. That Australopithecus walkedupright is also demonstrated by the footprint trail at Laetoli,(near Olduvai Gorge in northern Tanzania), where a largerand a smaller Australopithecuswalked together through wetmuddy ash 3.6 mya. Their stride may have been differentfrom ours, however, as their toes were still long and curvedfor climbing in the trees, and their legs were short com-pared to their arms.Only with Homo erectus at ca. 1.8 mya do we see a full-commitment to life on the ground and reduction or elimi-nation of many of the features that made it easier to getaround in the trees: longer arms, an upwardly orientedshoulder joint for hanging, and grasping toes with a lim-ited arch. The "Turkana bov" skeleton of an adolescentdated to 1 .5 mya has the long legs and basin-shaped pelvisof a fully bipedal human, while a slightly earlier foot skel-eton from Olduvai Gorge has short toes and a human-likearch. A recendy published set of footprint tracks in Kenyafrom 1.5 mya suggests real "toe-off" striding and a fully-
human arch. Variations in the pelvis after Homo erectus ap-parently have more to do with providing space for a larger-brained infant than with perfection of bipedal locomo-tion.Why Walk on Two Legs?Why did our lineage adopt this peculiar mode of gettingaround? It would not have made it any easier to escapefrom predators?most chimpanzees and all monkeys canoutrun us over short distances. An early argument held thatbipedalism developed to free the hands to make tools. Butas there is no sign of elaborate tool-making for a least thefirst 3-4 million years after the first bipedal members ofour lineage such as Sahelanthropus and Orrorin, it seems morelikely that later tool-makers took advantage of hands thatwere already partly freed. Another argument suggests thatbipedalism developed to facilitate moving between widely-spaced feeding trees, but Ardipithecus seems to have inhab-ited fairly dense woodland. Did we become bipedal to seeover the tall grass? (My own experience in the western RiftValley suggests that the grass in many places is more thansix feet high, and Lucy was about 3.5 feet tall.) Two othertheories that are plausible but difficult to demonstrate are1) that bipedalism makes a primate appear larger and morethreatening to potential challengers and predators (malegorillas run short distances on their hind legs to threatenintruders) or 2) that bipedalism makes it easier to carry
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food and infants to a safe place to feed (but see the com-ment on Ardi's likely closed woodland habitat, above). Andeven ifwe initially became capable of bipedal walking forone of the above reasons, why abandon the safety of thetrees altogether after 1.8 million years ago, since by thenour ancestors had lost their climbing toes, short legs, longarms and upwardly mobile shoulders for hanging frombranches?Born to Run?A new theory proposed by Bramble, Lieberman and col-leagues in a series of papers from 2004 on, is that it is notabout bipedal walking at all. Ratherwe were "born to run,"and it is running that constitutes one of several major ad-aptations that helped shape our bipedal morphology afterAustralopithecus. How can this be, as human runners are rela-tively slow. Human legs and feet are well-adapted, how-ever to endurance running. In jogging or "marathon-mode," the long spring-like tendons in our legs (such as theAchilles tendon) and the arches in our feet store and thenrelease energy like a spring during one part of the runningstep for later release. Our shorter toes are well-adapted forpushing off, while long legs make it possible to cover agiven distance in fewer steps. Finally our long waist andother structures allowed the upper body to counteract thetwisting forces generated by running and stabilize the body.This is why runners feel compelled to pump their armsback and forth in opposite directions to the correspondinglegs when they run. Also, a new (in H. erectus) ligament tothe back of the head stabilizes the head on the spine. Run-ning also makes maximum use ofour large gluteal muscles,which first become enlarged in the genus Homo, while walk-ing uses them only minimally.In addition to these adaptations in our lower limbs,specializations for heat loss allow us to run for exception-
ally long distances even in the middle of the day. Theseadaptations include our elongated bodies compared to apes,hair loss, increased number of sweat glands, mouth-breath-ing while running, and possibly adaptations of the circula-tory system to better cool the brain.Bramble and Lieberman compare our endurancerunning to trotting, which several running mammals areable to maintain for considerable periods of time. Well-conditioned humans, however, "trot" faster than dogs and
can even out trot horses in hot conditions. Mammals canmove faster when galloping than trotting, but they cannotpant and gallop at the same time. Since non-human mam-mals cool mostly by panting, they can die of heat exhaus-tion (hyperthermia) when forced to gallop for extendedperiods of time in the heat. The authors argue that ourhuman ability to run with long strides, sweating, and otherheat-loss adaptations account for why so many humans,even into their 70's and 80's, are able to run marathons.An ability to run long distances in the heat of the daywould have conferred considerable advantages on earlyhumans, who incorporated increasing amounts of meatinto their diets but seem to have lacked sophisticated weap-onry for hunting or for challenging other carnivores at kill
sites. In 2006, Liebenberg published a study of so-calledpersistence hunting by modern San peoples in the KalahariDesert in Botswana. (One of these hunts can be viewed at(http://www.youtube.com/watch?v=fUpo mA5RP8 .)Hunts in the heat of the day last from two to eight hoursof running after the animal through sand and brush overdistances of 25-35 km. at average speeds of 6-10 km/hour, which is not especially fast even by marathon stan-dards. At this point, the animal collapses from heat exhaus-tion, sometimes not even requiring the hunter to finish itoff. Since persistence hunting requires considerable track-ing abilities, has a risk of dehydration, and is rare amongmodern hunters, Pickering and Bunn challenged Brambleand Lieberman's scenarios. Did early humans who lived insavanna woodlands rather than in desert bushlands havethe ability to track animals as the San do? Lieberman andothers replied that even non-human carnivores have the
ability to follow prey, that following a wounded animalalso would have required tracking skills, and that persis-tence hunting even today is often more successful than hunt-ing with a bow and arrow. Further, hunters can carry waterin an ostrich eggshell or a skin bag. Did they actually rundown animals? We can only ask how they might have ac-quired large prey otherwise, without sophisticated weap-onry. Running may have developed out of an earlier adap-tation to bipedal walking as a way to cope with increasingaridity and use of open environments by our ancestorsafter 1.8 mya.
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Further work on running, much of it by Lieberman,his colleagues and students, has demonstrated that shortertoes lower the energetic cost of running but not of walk-ing, and that habitual barefoot runners (studied in Americaand Kenya) land on the balls of their feet (or sometimeson the mid-foot) rather than on the heel. Even with a highlycushioned modern running shoe, landing on the heel gen-erates more "shock" or force that travels up the leg, whilelanding on the forefoot almost entirely eliminates any colli-sional force on impact, making barefoot running comfort-able and easy to do on even the hardest surfaces. Studieson the developmental history of these adaptations in child-hood and on physiological effects of hormones on bonegrowth have also added to our understanding of this fun-damental and unique human adaptation.
ReferencesBennett, M.R., etal. 2009. Early Hominin Foot Morphol-ogy Based on 1 .5 Million-Year-Old Footprints from Ileret,Kenya. Science 323: 1 197-1201
.
Berger, L.R., eta/. 2010. Australopithecus sediba: A New Spe-cies of Homo-Like Australopith from South Africa. Science328: 195-204.Bramble, D.M., and Lieberman, D.E. 2004. EnduranceRunning and the Evolution of Homo. Nature 432: 345-352.Devlin, M. J., and D.E. Lieberman. 2007. Variation in Es-tradiol Level Affects Cortical Bone Growth in Responseto Mechanical Loading in Sheep. Journal of Experimental Bi-ology 2 10: 602-613.Liebenberg, L. 2006. Persistence Hunting by ModernHunter-Gatherers. CurrentAnthropology 47 (6): 1017-1025.Lieberman, D.E., and DM. Bramble. 2007. The Evolu-tion of Marathon Running Capabilities in Humans. SportsMedicine 37(4-5): 288-290.Lieberman D.E., eta/. 2007. The Evolution of EnduranceRunning and the Tyranny of Ethnography: A Reply toPickering and Bunn. Journal of Human Evolution 53: 439-442.Lieberman D.E., et a/. 2006. The Human Gluteus Maxi-mus and Its Role in Running. Journal of ExperimentalBiology209:2143-2155.
Lieberman, D.E. etal. 2010. Foot Strike Patterns and Col-lision Forces in Habitually Barefoot Versus Shod Runners.Nature 463: 531-535.
Pickering, T.R., and H.T Bunn. 2007. The Endurance Run-ning Hypothesis and Hunting and Scavenging in Savanna-Woodlands. Journalof Human Evolution 53: 434-438.Richmond, B.G, and W.L. Jungers. 2008. Orrorin tugenensisFemoral Morphology and the Evolution of Hominin Bi-pedalism. Science 318: 1662-1665,
Rolian, C, etal. 2009. Walking, Running and the Evolutionof Short Toes in Humans. Journal of Experimental Biology212:713-721.White, T.D., et al. 2009. Ardipithecus ramidus and thePaleobiology of Early Hominids. Science 326: 75-86. (Seealso articles in the same issue by Lovejoy, O. et al?)ZollikoferC.P.E., et al. 2005. Virtual Cranial Reconstruc-tion of Sahelanthropus tcbadensis. Nature 434: 755-759.
Alison S. Brooks is professor of anthropology at GeorgeWashington University and editor of 'AnthroNotes"
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