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Human Evolution
The Oxford debate 1860
Thomas Henry Huxley, nicknamed 'Darwin's bulldog', was championing Charles Darwin's
revolutionary concept of evolution by natural selection, published less than a year before
...
Both sides claimed victory, and the debate
continues to this very day
...
Who
made so ill a use of his wonderful speaking powers to try and burke, by a display of
authority, a free discussion on what was, or was not, a matter of truth”
Paleoanthropological story – Lucy
During the 1960s and 1970s, hundreds of fossils were found, particularly in East
Africa in the regions of the Olduvai gorge and Lake Turkana
...
They found "Lucy", the most complete fossil member of the species Australopithecus
afarensis
...
All arisen from a single ancestral type that once lived on a continent now submerged
beneath the Indian Ocean
...
Single dispersal?
2
...
Dispersal from North or South?
OR a multiregional origin of modern humans which allows for a much greater role for
hybridisation
...
Roughly 100,000 years ago, the Old World was occupied by a morphologically diverse group
of hominids
...
However, by 30,000 years ago this taxonomic diversity vanished and humans everywhere
had evolved into the anatomically and behaviorally modern form
...
Understanding the issue
Multiregional theory: homo erectus left Africa 2 mya to become homo sapiens in different
parts of the world
...
This model contains the following components:
-‐ Some level of gene flow between geographically separated populations prevented
speciation, after the dispersal
-‐ All living humans derive from the species Homo erectus that left Africa nearly two
million-‐years-‐ago
-‐ Natural selection in regional populations, ever since their original dispersal, is
responsible for the regional variants (sometimes called races) we see today
-‐ The emergence of Homo sapiens was not restricted to any one area, but was a
phenomenon that occurred throughout the entire geographic range where humans
lived
In contrast, the Out of Africa Model asserts that modern humans evolved relatively recently
in Africa, migrated into Eurasia and replaced all populations which had descended
from Homo erectus
...
-‐ After Homo erectus migrated out of Africa the different populations became
reproductively isolated, evolving independently, and in some cases like the
Neanderthals, into separate species
-‐ Homo sapiens arose in one place, probably Africa (geographically this includes the
Middle East)
-‐ Homo sapiens ultimately migrated out of Africa and replaced all other human
populations, without interbreeding
Modern human variation is a relatively recent phenomenon
The multiregional view posits that genes from all human populations of the Old World
flowed between different regions and by mixing together, contributed to what we see today
as fully modern humans
...
As these peoples migrated they replaced all other
human populations with little or no interbreeding
...
What’s wrong with mitochondrial Eve?
• Africa has greater genetic diversity because its prehistoric population was probably
larger
• Assumes genetic diversity reflects age of a population rather than population size
• Differences in ancient population size could mimic a recent African origin of modern
humans