Transcript Modern Humans

Modern Humans
Homo sapiens
Origin Theories
Time Line
Homo sapiens
(ca. 200 kya…)
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Fully modern humans
Upper Paleolithic tool technology
Elaborate Cave Art
Homo sapiens sites in Europe
Transformation
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Reduced robusticity-everything gets
smaller
Back teeth continue to reduce, so do front
teeth
Cranial buttresses much less in evidence
• loss of brow ridge
• development of chin
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Sexual dimorphism reduces to modern
levels
Homo sapiens
What causes this overall reduction?
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Teeth and cranial
buttresses: food
processing
• Especially cooking
technology
• Earth ovens
• Reduced selection for big
molars
What causes this overall reduction?
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Skel. robust. & sex. dimorph.: projectiles
& string
• With modern humans, first projectile weapons
• Atlatl (spear-thrower)
• No close quarter killing of big-game
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Selection reduced for maintaining big
bones
Sex. dimorph: males get relatively smaller
Atlatl
http://www.crt.state.la.us/archaeology/POVERPOI/food.htm
Cro Magnon
Species:
Homo sapiens
Age:
~30,000 years
Date of
Discovery:
March 1868
Location:
Les Eyzies,
Dordongne,
France
Discovered
by:
Louis Lartet
Skuhl 5
Species:
Age:
Date of
Discovery:
Homo sapiens
~ 90,000 years
May 2, 1932
Location:
Mount Carmel,
Israel
Discovered by:
T. McCown and
H. Moivus,
Jr.
Upper Paleolithic Tools
Upper Paleolithic Tools
Multiregional Theory
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H. erectus left Africa, spread to other
areas of the world, and evolved into
modern humans.
Human populations linked throughout the
world were linked by gene flow.
• Caused modern humans to evolve as a single
species from H. erectus to H. sapiens all over
the world.
• Also separated by distance and environment so
had considerable regional variation in
morphology.
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All genes arose in many parts of the world
and were mingled together as people from
different regions mated.
Replacement Theory
(Eve Hypothesis)
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Hominid populations genetically separated
during the Middle Pleistocene (before
200,000 B.P.), evolving independently.
• Between 100,000 and 200,000 years ago
modern humans evolved in Africa and spread
out, replacing archaic H. sapiens.
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Little or no gene flow as modern humans
replaced local populations, all genes
necessary for moderns assembled in Africa.
“Mostly” Out of Africa
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Modern Humans evolved in Africa around
150,000 years ago.
Spread to Asia, Middle East and Europe
and replaced earlier settlers.
In Europe, with Neanderthals, this may
have been complicated by absorption of
Neanderthals into the Modern gene pool.
• This allowed a very few Neanderthal traits to
persist in living populations in very small
percentages.
Lagar Velho 1 Skeleton
Neanderthal/Human Hybrid??
•Analysis of the skeletal remains
of this four-year-old boy has
revealed that he may be a
Neandertal-Cro-Magnon hybrid.
•Found in a Portuguese rockshelter and dating to 25,000 to
24,500 years ago has yielded
startling evidence that early
modern humans and Neandertals
may have interbred.
•While the boy's prominent chin,
tooth size, and pelvic
measurements marked him as a
Cro-Magnon, or fully modern
human, his stocky body and short
legs indicate Neandertal heritage,
according to Erik Trinkaus, a
paleoanthropologist at
Washington University in St.
Louis.
Lagar Velho 1 Skeleton
Presence of artifacts in burial also a modern trait.
Chin-on Lagar Velho Specimen,
not on Neanderthals
Lagar Velho 1
Evidence: Fossils
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Evidence from Europe and Middle
East is inconsistent with Multiregional
model.
• long period of overlap between
Neanderthal and moderns in this area.
• anatomically modern people appeared
60,000 years before Neanderthals
disappeared.
Evidence: Archaeological
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Cave sites in Israel, most notably Qafzeh
and Skhul date to nearly 100,000 years
and contain skeletons of anatomically
modern humans.
Qafzeh Cave
Amud and Kebara
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The presence of Neanderthals at two other
caves in Israel, Amud and Kebara, dated
to roughly 55,000 years means that
Neanderthals and Homo sapiens
overlapped in this region for at least
45,000 years.
Therefore, if Homo sapiens were in this
region for some 45,000 years prior to the
disappearance of the Neanderthals, there
is no reason to assume that Neanderthals
evolved into modern humans.
Amud Cave, Israel
Evidence: Tools/Culture
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Tools associated with moderns are not found
with Neanderthals.
A remarkable diversity in stone tool types for
moderns.
• tool types showed significant change over time and
space
• artifacts were regularly fashioned out of bone,
antler and ivory, in addition to stone
• stone artifacts were made primarily on blades and
were easily classified into discrete categories,
presumably reflecting specialized use
Bone
Tools
Upper Paleolithic tools
Aurignacian
blades
Dufour bladelet
Bone point
Tools/Culture con’d
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Burials were accompanied by ritual
or ceremony and contained a rich
diversity of grave goods
Living structures and well-designed
fireplaces were constructed
Raw materials such as flint and shells
were traded over some distances
Double Burial from Skuhl (adult
female and young child)
Genetic Evidence
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Contemporary patterns of genetic
variation provide clues to origins of
modern humans
Mitochondrial DNA (mtDNA) passed
from mother to her children, an exact
copy of genetic material.
Humans are less genetically variable
than other populations-suggests
population explosion.
Genetic Evidence, con’d
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The high degree of similarity
between human populations stands
in strong contrast to the condition
seen in our closest living relatives,
the chimpanzees.
In fact, there is significantly more
genetic variation between two
individual chimpanzees drawn from
the same population than there is
between two humans drawn
randomly from a single population.
Genetic Evidence
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In support of an African origin for Homo
sapiens the work of Cann and Wilson has
demonstrated that the highest level of genetic
variation in mtDNA occurs in African
populations.
This implies that Homo sapiens arose first in
Africa and has therefore had a longer period of
time to accumulate genetic diversity.
Using the genetic distance between African
populations and others as a measure of time,
Homo sapiens arose between 100,000 and
200,000 years ago in Africa.
Genetic Evidence
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The low amount of genetic variation
in modern human populations
suggests that our origins may reflect
a relatively small founding population
for Homo sapiens.
Analysis of mtDNA by Rogers and
Harpending supports the view that a
small population of Homo sapiens,
numbering perhaps only 10,000 to
50,000 people, left Africa somewhere
between 100,000 and 200,000 years
ago.
Neanderthal mtDNA
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Scientists recently succeeded in extracting
DNA from several Neanderthal skeletons.
• After careful analysis of particularly the
mtDNA, but now also some nuclear DNA, it is
apparent that Neanderthal DNA is very distinct
from our own.
• In assessing the degree of difference between
DNA in Neanderthals and modern humans, the
authors suggest that these two lineages have
been separated for more than 400,000 years.
Implications
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Suggestions from mtDNA
• Human populations spread out across
the globe well before any major
population expansion took place.
• Size of pop before expansion was
between 10 and 50,000 people.
• Major expansion of people beginning
around 100,000-200,000 years ago in
Africa and 50,000 years ago in the rest
of the world.
Why important?
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Resolution of this controversy because it affects
our view of contemporary human variation.
Affects our perspective about the significance of
genetic differences and modern human
populations.
If replacement model correct, then all humans
descended from a lineage that arose around
100,000-200,000 years ago.
If multiregional correct then humans related as
long as 1 million years ago and arose separately
from there.