ANG 6930 Proseminar in Anthropology IIA: Bioanthropology

Mulligan, Copyright 2011 All rights reserved

ANG 6930Proseminar in

Anthropology IIA: Bioanthropology

Day 5

ANG 6930

Prof. Connie J. Mulligan

Department of Anthropology


This week• Hominoid to hominin

• Dating the ape-human split• Australopiths• Early hominin subsistence and social organization• Origins of genus Homo• Homo erectus• Neanderthals and other archaic humans

• Reading– The Human Species, Chpts 9 (Primate origins and evolution), 10 (Beginnings of

human evolution), 11 (Origin/evolution of genus Homo)

– Course packet• “A new kind of ancestor: Ardipithecus unveiled”, Science, 326:36-40.• “Candidate human ancestor from South Africa sparks praise and debate”, Science• Klein RG. 2009. Darwin and the recent African origin of modern humans. PNAS 106:16007-

16009.• “New statistical model moves human evolution back three million years” ScienceDaily,

11/9/2010.• Teaford MR and Ungar PS. 2000. Diet and the evolution of the earliest human ancestors. PNAS

97:13506-13511.• Conroy GC. 2002. Speciosity in the early Homo lineage: Too many, too few, or just about right?

Journal of Human Evolution 43:759-766.• Premo LS and Hublin J-J. 2009. Culture, population structure, and low genetic diversity in

Pleistocene hominins. PNAS 106:33-37.• Hublin JJ. 2009. The origin of Neanderthals. PNAS 106:16022-16027.• “Tales of a prehistoric human genome” Science 2009, 323:866-871.• Optional– Noonan JP. Neanderthal genomics and the evolution of modern humans.


Next week• Origin of modern humans/Human biodiversity and race

• Homo floresiensis• Anatomically modern Homo sapiens• African replacement or multiregional evolution?• Global patterns of human genetic variation• Anthropological critique of race

• Reading– The Human Species, Chpts 12 (Origin of modern humans), 13 (Human

variation), 14 (Genetics, history and ancestry)

– Course packet• Tattersall I. 2009. Human origins: Out of Africa. Proceedings of the National

Academy of Sciences 106:16018-16021.• Powledge TM. 2006. What is the Hobbit? PLoS Biology. 4:2186-2189.• Scheinfeldt L et al. 2010. Working toward a synthesis of archaeological,

linguistic, and genetic data for inferring African population history. Proceedings of the National Academy of Sciences 107:8931-8938.

• Serre D and Pääbo S. 2004. Evidence for gradients of human genetic diversity within and among continents. Genome Research 14:1679-1685.

• Haak W. 2008. Ancient DNA, strontium isotopes, and osteological analyses shed light on social and kinship organization of the Later Stone Age. PNAS. 105:18226-18231.

• “On the origin of art and symbolism” Science 2009, 323:709-711.


Hominoid to Hominin


Overview

• Origin of hominins in late Miocene– Ardipithecus– Orrorin– Sahelanthropus

• Plio-pleistocene hominin adaptive radiation– Australopithecus– Paranthropus– Kenyanthropus

• Hominin phylogenies

• Evolution of bipedalism


Overview of hominid evolution


Climate change in late Miocene/PlioceneHominids evolved ~6 mill yrs ago


Late Miocene to Early Pliocene• Apes flourished in Miocene, but most genera became extinct

• Falling temperatures changed climate in African tropics– Rain fall declined, became more seasonal– Tropical forests shrank; woodlands, grasslands expanded

• Ecological pressures led to evolution of first hominids about 6-8 mya


What makes a hominid?• Human uniqueness long defined in terms of

brain evolution

• Now clear that bipedalism predates big brains by several million years

• Bipedalism associated with morphological changes

• Dietary changes associated with new habitats, also reflected in different chewing apparatus


Shared, derived traits of hominids

• Habitual bipedalism

• Chewing apparatus– Wide parabolic dental arcade– Thick enamel– Reduced canines– Larger molars in relation to other teeth

• Much larger brains relative to body size

• Slow development with long juvenile period

• Elaborate, highly variable material and symbolic culture, transmitted in part through spoken language


Major discoveries of hominidsMainly South Africa and East Africa


New discoveries of hominids 5-7 mya

• (Ardipithecus ramidus– 1992– Middle Awash in Ethiopia– Previously thought to be older than 5

mya, now 4.4 mya)

• Orrorin tugenensis– 2001– Tugen Hills in Kenya

• Sahelanthropus tchadensis– 2002– Toros-Menalla in Chad

• Ardipithecus kadabba– 2004– Middle Awash in Ethiopia


Sahelanthropus tchadensis

• Discovered in 2002 by Michel Brunet and colleagues

• New dental and mandibular specimens reported in 2005

• Estimated 6-7 mya in Chad, not securely dated– Fits with humans if older human-

chimp divergence is used

• Unique mix of humanlike and apelike features– Relatively flat face and massive

brow ridge– Small brain, primitive teeth, back

of skull very apelike• No postcranial fossils known• Could be hominoid, not hominid

Toumaï


Orrorin tugenensis

• Announced in 2001 by Senut and Pickford

• 6 mya at Tugen Hills in Kenya

• No cranial fossils recovered– Keep controversy alive (could be

ardipithecus)

• Mixture of apelike-humanlike– Incisors, canines, premolars,

arm and fingers like chimpanzees

– Thick enamel, femur humanlike

• Bipedalism inferred from femur anatomy


Ardipithecus kadabba

• 1st designated as subspecies, then promoted to full species in 2004

• Even older - 5.8 – 5.2 Ma• Ethiopia (Middle Awash)• Similar to Sahelanthropus in

mix of features• Slightly smaller Canine• Wooded habitat

Yohannes Haile-Selassie


Ardipithecus ramidusFirst identified and named in 1994 – thought to be older than 5 mya

15 years to excavate >100 fragments and reassemble them, e.g. >1000 hours on skull (Gen Suwa) – 4.4 mya

Nature 371: 306-312 (1994)



Ardipithecus ramidus – “ARDI”• 4.4 mya• Discovered in Middle Awash

– Aramis (Ethiopia)• Most complete skeleton

older than Lucy• Not Homo and not

Australopithecus• Similarities to

Sahelanthropus– Very early stage of human

evolution


Unexpected anatomy

White, Gibbons (2009) A new kind of ancestor: Ardipithecus unveiled. Science


White, Gibbons (2009) A new kind of ancestor: Ardipithecus unveiled. Science


Significance of late Miocene hominids• Pushes back fossil record of hominids by 2-3 million

years– Until early 1990s, earliest hominids were < 4 mya

– Now appears that multiple, diverse hominids may date to late Miocene

• Forces rethinking of bipedalism– Early hominids appear to have inhabited forested

environments, not open savannas

– Challenges some scenarios for adaptive value of bipedalism

• Having hand free to use tools doesn’t seem important since bipedalism predates tool use by 3.5 my


Diversification of hominids

• Hominid lineage proliferated 4–2 mya, likely with multiple species living in Africa at a time

• Taxonomic classification of these hominids hotly contested– Lumpers and splitters– Linear and bushy family trees

• Bernard Wood and Mark Collard advocate three genera– Australopithecus, Paranthropus, Kenyanthropus


Australopithecus

• Debate about how many species belong to genus

• Two major points of disagreement– Robust australopithecines– Early Homo

• Wood and Collard’s scheme narrows definition of Australopithecus and of Homo

• Taxonomic debates reflect limitations of data, philosophical differences, and politics


Primitive and later hominids

• Primitive hominids– Australopithecus anamensis– Australopithecus afarensis– Kenyanthropus platyops

• Later hominids– Paranthropus or robust Australopithecus– Australopithecus africanus– Australopithecus garhi– Australopithecus habilis, A. rudolfensis


Australopithecus anamensis

• Earliest species of genus to be found• Dated to 4.2-3.8 mya near Lake Turkana in

Kenya (Leakey et al. 1995, 1998)

• Bipedalism inferred from knee and ankle joints– Thick enamel and smaller canines– Arm bone suggests primitive arboreal

adaptations– Dental arcade and chin chimpanzee-like

• Primitive characters suggest A. anamensis may be ancestral to later australopithecines


Australopithecus afarensis• Most well-known australopithecine =

Lucy– Most complete skeleton (40%)

• Dates to 3.5-2.3 mya in East Africa (Don Johanson, 1970s)

• Bipedalism– Shape of pelvis, femur, foot, Laetoli footprints– May not have been fully modern gait

• Derived characters intermediate between humans and chimps– Dental arcade– Canines– Premolar cusps


Laetoli footprints

• Formed and preserved by a chance combination of events -- a volcanic eruption, a rainstorm, and another ashfall– Tanzania

• Two individuals, possibly three– Fainter of two clear trails is unbalanced,

individual possibly burdened on one side w/ an infant?

• A. afarensis– No other hominid near this age, 3.6 mya


Kenyanthropus platyops

• Dated to 3.5-3.2 mya on western side of Lake Turkana (Leakey et al. 2001)

• Mosaic of features– Small ear hole (like early

Australopithecus)– Thick enamel (like later

Australopithecus)– Relatively flat face (like later

hominids)– Apart from brain size, is similar to

Homo rudolfensis

KNM-WT 40000


Robust hominids• Robust early hominids have crania

and teeth specialized for heavy chewing– Sagittal crest– Flared zygomatic arches– Massive mandibles and molars

• Debate over proper genus (Australopithecus or Paranthropus)

– Paranthropus aethiopicus– Paranthropus robustus– Paranthropus boisei

KNM-ER 17000


Who became Homo?

• General agreement that the robust australopithecines became extinct ~1 mya and did not give rise to modern humans

• Who did?– Three major candidates

• Australopithecus africanus• Australopithecus garhi• Australopithecus sebida


Australopithecus africanus• First known australopithecine (Dart

1925)

• Dated to 3-2.2 mya in South Africa

• More apelike physique than A. afarensis– Arms longer than legs – arboreality

– Some adaptations for heavy chewing

• Probably like other australopiths, matured rapidly like chimpanzees

• One candidate for immediate ancestor to Homo

Taung Child


Australopithecus garhi• Dated to around 2.5 mya in East Africa

(Asfaw et al. 1999)

• Small brains like A. afarensis and A. africanus

• Very prognathic face, larger teeth, sagittal crest

• Some evidence that made stone tools and used to cut meat from bones, extract marrow

• Other candidate for immediate ancestor to Homo

BOU-VP-12/130


Known dates for hominid species


Hominid phylogenies

Gibbons, Ann. 2002. "In Search of the First Hominids." Science 295:1214-1219.


Science online extras


Hominid to Homo


Genus Homo

• Increased brain size

• Reduction in size of face and teeth

• Increased reliance on cultural adaptations


Evolution of brain size


Brain size in fossil hominids


Proposed species of Homo


Homo erectus

• “upright walking human”• Appeared in Africa 1.7-1.8 mya

– Possibly as young as 50kya = co-existence w/ moderns

• First hominid to migrate out of Africa into temperate parts of Eurasia 1.8 Ma – 500 kya

• Primitive cranial traits include large brow ridges, postorbital constriction, flat cranial vault

• Derived traits include less prognathism, higher skull vault, smaller teeth, larger brain, modern limb proportions


H. erectus/ergaster sites


KNM-WT 15000

• Most complete H erectus skeleton

• “Turkana boy”• ~ 12 years of age• Evidence of modern limb

proportions• Tall• Large brain• Appears to be juvenile,

not adolescent


Origins of stone tools• Earliest evidence for intentionally modified stone tools is 2.5

mya in East Africa

• Earliest stone tools in South Africa ~ 2 mya

• Bone tools appear 2-1 mya at Olduvai Gorge (Tanzania) and in South Africa

• Oldowan tool technology

– H habilis and H rudolfensis

• Acheulean tool technology

– H erectus


Oldowan tool industry

• Mode 1 technology

• Simple tools made from rounded stones, flaked to produce sharp edge

• Variable form


Importance of Oldowan hominids

• Plausible candidates for link between early apelike hominids and later hominids

• Studying Oldowan archaeological sites yields insight in processes shaping human evolution

• Combining archaeology, ethnography, and biological anthropology informs understanding of transition to modern humans


Oldowan hominids relied on hunting and extractive foraging

• Kathy Schick and Nicholas Toth (Indiana)

• Experimental studies of Oldowan tool use

• Flakes, not cores, may be most important tools

• Useful for many functions, including butchering


Bone tools used to dig up bulbs, tubers, excavate termite mounds

Swartkrans


Archaeological evidence for meat eating

• Oldowan sites at Olduvai Gorge littered with fossilized animal bone from many species

• Taphonomic studies suggest most fossils not accumulated by natural processes

• Taphonomic studies also show evidence that Oldowan hominids processed carcasses


Taphonomy shows hominids used Oldowan tools to process carcasses

Cut marks made by carnivore teeth Cut marks made by stone tools

Electron micrographs of 1.8 mya fossil bones from Olduvai Gorge


Hunters or scavengers?• Controversy over whether Oldowan hominids

were hunters or scavengers• Comparative perspective

– Most large mammalian carnivores practice both hunting and scavening

– No mammalian carnivore subsists entirely by scavenging

• Taphonomic studies provide evidence of both hunting and scavenging– Cut marks on meaty limb bones not usually left to

scavengers


Types of Food Resources

• Collected foods are simply collected and eaten (e.g., ripe fruit or leaves)

• Extracted foods must be processed (e.g., fruits in hard shells, tubers, or termites)

• Hunted foods must be caught or trapped (e.g., vertebrate prey)

Vary in amount of knowledge and skill required to obtain


Chimpanzee and Human Foraging Patterns


Contemporary foraging patterns

• Contemporary human foragers get most calories from extracted or hunted resources

• Provide high nutritional quality, but require difficult and time-consuming skills– Aché men reach peak hunting efficiency at age 35– Hadza women achieve maximum efficiency in root

acquisition at 35-40 years old

• Shapes human life history and division of labor


Hunting and foraging favors food sharing and division of labor

• In contemporary foragers, extensive food sharing and sexual division of labor

• Division of labor– Difficult skills require time to learn – Child care more compatible with

gathering

• Meat eating favors food sharing


Sexual division of labor in contemporary foragers


Neanderthals

• Neander Valley• H sapiens neanderthalensis or

H neanderthalensis– Closest to modern humans other

than Cro Magnon

• Lived throughout Europe and the Middle East, 150-28 kya– Overlapped with modern humans

in space and time


The Neander Valley, east of Dusseldorf in Germany, was the location for the discovery of Neandertal 1, the original Neandertal type specimen, in 1856, during the removal of deposits from the Kleine Feldhofer Grotte.


H. heidelbergensis sites



Early H. sapiens sites


Skull morphology of Homo


Skeletal features of Neandertals and modern humans


Taxonomic troublesNumber of Species

Relethford Minimum Current Maximum

Homo erectus Early Homo sapiensHomo erectusHomo ergaster

Archaic humans Archaic Homo sapiens

Homo antecessorHomo heidelbergensisHomo neanderthalensis

Modern humans Recent Homo sapiens Homo sapiens


Hominid phylogenies

Milford Wolpoff G. Phillip Rightmire Richard Klein


Molecular genetic data on the Neanderthals and implications for

gene flow with modern humans

• > 15 Neanderthal mtDNA genome sequences

• 2 Cro-Magnon mtDNA control region sequences

• 2 (low coverage) Neanderthal nuclear genome sequences

• 1 Denisova mtDNA genome sequence


Multidimensional scaling of HVRI sequences of 60 modern Europeans (filled squares), 20 modern non-Europeans (filled circles), 4

Neanderthals (open diamonds), Lake Mungo specimen (open circle), and Paglicci specimens (open squares)

Conclusion - Modern humans clearly group w/ Cro-Magnon and show no shared ancestry with Neanderthal

Caramelli et al. 2003

Neanderthal

Cro-Magnon


Inconsistencies between the two Neanderthal nuclear genome draft sequences

Noonan et al. 2006 Green et al. 2006

• Human-Neanderthal DNA sequence divergence time approximately 706 kya

• 0% contribution of Neanderthals to human gene pool

• Neanderthal sequence carries derived allele for 3% contribution to modern human SNPs

• Modern European-Neanderthal population split time of 325 kya

• Human-Neanderthal DNA sequence divergence time approximately 516 kya

• Significant evidence of Neanderthal-human gene flow

• Neanderthal sequence carries derived allele for 30% contribution to modern human SNPs

• Modern European-Neanderthal population split time of 35 kya


New in Science last week• New genomic data are settling an old argument about how our species evolved.

http://www.sciencemag.org/cgi/content/summary/331/6016/392 – Two instances of interbreeding

• w/ Neanderthal• w/ Denisova populationNew DNA data suggest not one but at least two instances of interbreeding

between archaic and modern humans, raising the question of whether Homo sapiens at that point was a distinct species

– Refutes complete replacement– Doesn’t prove classic multiregionalism– Suggests a small amount of interbreeding, presumably at the margins where invading moderns

met archaic groups, the ‘assimilation’ model

Modern humans from Africa interbred with Neandertals (pink). Then one group mixed with Denisovans (green) on the way to Melanesia.

Gibbons, Science 2011


New in Science last week

• The Species Problem Our ancestors are now thought to have mated with at least two kinds of archaic humans at two different times and places. Were they engaging in interspecies sex, or does the fact that they were able to produce offspring mean they were all members of the same species? http://www.sciencemag.org/cgi/content/summary/331/6016/394– Paabo says such a discussion is a “sterile academic endeavor”– John Hawks – “They mated with each other. We'll call them the

same species”– Hublin says Mayr's concept doesn't hold up: “There are about

330 closely related species of mammals that interbreed, and at least a third of them can produce fertile hybrids.”


Bottom line

• Most likely, some low level of interbreeding between Neanderthals (and other archaics?) with modern humans

• Evidence of this genetic contribution will be present at low frequency and patchily distributed geographically

Documents

ANG 6930 Proseminar in Anthropology IIA: Bioanthropology