
DNA extracted from ancient African skeleton shows mixing with Eurasians - okfine
http://news.sciencemag.org/evolution/2015/10/first-dna-extracted-ancient-african-skeleton-shows-widespread-mixing-eurasians
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themgt
More support for the "Out of Arabia" scenario [1], the implications of which
are enormous and potentially awkward.

[1] [http://dienekes.blogspot.com/2015/08/rethinking-dispersal-
of...](http://dienekes.blogspot.com/2015/08/rethinking-dispersal-of-homo-
sapiens.html)

~~~
meric
How so could it be awkward?

~~~
themgt
(as a layman) The original Out of Africa hypothesis had the "happy conclusion"
that anatomically modern humans (AMH) evolved in a small group within Africa
and then migrated out to populate the rest of the world, displacing (and not
interbreeding with) older hominids. And everyone on earth is a descendent of
that small first group, so we're all one coherent happy family.

The evolving picture today appears much more likely that some not-quite AMHs
migrated from Africa to Arabia where they lived alongside and interbred with
already-present Neanderthal culture, became anatomically modern and developed
Upper Paleolithic tools/culture (which were perhaps actually an evolution of
Neanderthal culture), spent a while fairly isolated and evolving in Arabia,
and eventually as AMHs migrated out to displace/interbreed with the planet's
other hominids.

So, awkward because it's a much more complex, convoluted story, with a lot
more space for different populations of humans to have significant genetic
differences. You're also left with Africa potentially having a population of
pre-AMH homo sapiens and other hominids, with only quite recent back-migration
admixing in "modern human" DNA.

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JoeAltmaier
Is it fair to say that _anatomically modern_ humans happened after leaving
Africa? Sure some more changes happened; change continued in Africa as well.
And the Neanderthal 2-6% is probably not that significant.

Another interpretation is, moving to Northern climates with reduced sunlight
resulted in decreased melanin (to ensure sufficient vitamin D) which allowed
more ultraviolet damage thus increased mutations (blue eyes, red hair and so
on). In this view, Africa retains 'modern human anatomy'; the rest of the
world is a sort of Galapagos Bird situation.

~~~
dmm
I don't understand percentages used to describe genetic similarity. I mean I
heard that humans share 50% with bananas and 96% with chimpanzees.

So if 4% is the difference between humans and chimps then 2-6% can be very
significant, right? Or can those numbers even be compared?

~~~
dogma1138
The percentage difference is calculated using a very odd system which ignores
all the actual differences.

For example if Humans and Bananas each have 5000 coding genes in common the
difference will be measured only on those genes we actually share (out of
20-25K coding genes in humans, no clue how many coding genes do bananas have),
so the difference is actually much greater than the 50%, 4%, 1% or what ever
figure you get because the big differences are simply discarded.

These days there's a cartoon for everything :)
[https://www.youtube.com/watch?v=IbY122CSC5w](https://www.youtube.com/watch?v=IbY122CSC5w)

And this is without even going into gene expression and epigentics which play
a role which some might even consider to be bigger than what actual genetic
data you might happen to carry along with you.

Heck chickens still have the genes to grow teeth and feathered scales like the
dinosaurs they've evolved from however these genes are not expressed anymore
in nature.

