Transcript Molecular Genetics - University of Florida

ANG 6930
Proseminar in
Anthropology IIA:
Bioanthropology
Day 5
ANG 6930
Prof. Connie J. Mulligan
Department of Anthropology
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This week
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Hominoid to hominin
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Dating the ape-human split
Australopiths
Early hominin subsistence and social organization
Origins of genus Homo
Homo erectus
Neanderthals and other archaic humans
Reading
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The Human Species, Chpts 9 (Primate origins and evolution), 10
(Beginnings of human evolution), 11 (Origin/evolution of genus Homo)
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Course packet
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“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 106:1600716009.
“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.
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Optional– Noonan JP. Neanderthal genomics and the evolution of modern humans.
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Next week
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Origin of modern humans/Human biodiversity and race
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Homo floresiensis
Anatomically modern Homo sapiens
African replacement or multiregional evolution?
Global patterns of human genetic variation
Anthropological critique of race
Reading
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The Human Species, Chpts 12 (Origin of modern humans), 13 (Human
variation), 14 (Genetics, history and ancestry)
Course packet
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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. Mulligan, Copyright 2011
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Hominoid to Hominin
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Overview
• Origin of hominins in late Miocene
– Ardipithecus
– Orrorin
– Sahelanthropus
• Plio-pleistocene hominin adaptive radiation
– Australopithecus
– Paranthropus
– Kenyanthropus
• Hominin phylogenies
• Evolution of bipedalism
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Overview of hominid evolution
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Climate change in late Miocene/Pliocene
Hominids evolved ~6 mill yrs ago
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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
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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
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Shared, derived traits of hominids
• Habitual bipedalism
• Chewing apparatus
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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
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Major discoveries of hominids
Mainly South Africa and East Africa
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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
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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 humanchimp 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
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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
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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
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Ardipithecus ramidus
First 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)
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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
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Unexpected anatomy
White, Gibbons (2009) A new kind of ancestor: Ardipithecus unveiled.
Science
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White, Gibbons (2009) A new kind of ancestor: Ardipithecus unveiled.
Science
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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
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since bipedalism predates tool use by 3.5 my Mulligan,
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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
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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
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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
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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 chimpanzeelike
• Primitive characters suggest A.
anamensis may be ancestral to later
australopithecines
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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
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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
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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
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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
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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
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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 Mulligan, Copyright 2011
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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
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Known dates for hominid species
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Hominid phylogenies
Gibbons, Ann. 2002. "In Search of the First Hominids." Science 295:1214-1219.
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Science online extras
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Hominid to Homo
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Genus Homo
• Increased brain size
• Reduction in size of face and teeth
• Increased reliance on cultural adaptations
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Evolution of brain size
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Brain size in fossil hominids
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Proposed species of Homo
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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
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H. erectus/ergaster sites
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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
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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
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Oldowan tool industry
• Mode 1 technology
• Simple tools made
from rounded stones,
flaked to produce
sharp edge
• Variable form
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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
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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
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Bone tools used to dig up bulbs, tubers,
excavate termite mounds
Swartkrans
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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
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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
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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
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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
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Chimpanzee and Human Foraging
Patterns
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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
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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
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Sexual division of labor in
contemporary foragers
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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
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The Neander Valley, east of Dusseldorf in Germany, was the location for the
discovery of Neandertal 1, the original Neandertal type specimen, in 1856, Mulligan, Copyright 2011
during the removal of deposits from the Kleine Feldhofer Grotte.
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H. heidelbergensis sites
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Early H. sapiens sites
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Skull morphology of Homo
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Skeletal features of Neandertals
and modern humans
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Taxonomic troubles
Number of Species
Relethford
Minimum
Current Maximum
Early Homo sapiens
Homo erectus
Homo ergaster
Archaic humans
Archaic Homo sapiens
Homo antecessor
Homo heidelbergensis
Homo
neanderthalensis
Modern humans
Recent Homo sapiens
Homo sapiens
Homo erectus
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Hominid phylogenies
Milford Wolpoff
G. Phillip Rightmire
Richard Klein
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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
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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
Cro-Magnon
Neanderthal
Caramelli et al. 2003
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Inconsistencies between the two Neanderthal
nuclear genome draft sequences
Noonan 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 EuropeanNeanderthal population split
time of 325 kya
Green et al. 2006
• 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 EuropeanNeanderthal population split
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time of 35 kya
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New in Science last week
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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
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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/331/601
6/394
– 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.”
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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
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