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1 freetoken  Oct 23, 2014 10:52:15am

I don’t know what the author is trying to get at here:

Before now we couldn’t rule out that our fraction of Neanderthal ancestry was the result of interbreeding between Neanderthals and modern humans who were in the near east before Neanderthals got there, says David Reich from Harvard University, a co-author on the paper. While these near-eastern humans were anatomically modern, they did not show modern behaviour, he says.

I’m not sure that has been communicated clearly.

2 Greup  Oct 23, 2014 12:21:46pm

“About 2 per cent of many people’s genomes today is made up of Neanderthal DNA, a result of interbreeding between the two species that can be seen in everyone except people from sub-Saharan Africa. “

I always find this very funny. All the nazis and white supremasists always talk a lot about about the purity of the white race and so on…

Turns out that the only truly pure Homo Sapiens are the black guys who never left afrika in prehistoric times….everyone else are truly bastards…

Ah the Irony.

3 CriticalDragon1177  Oct 23, 2014 1:06:37pm

re: #2 Greup

Actually from what I understand Neanderthal genes did end up in sub Saharan African populations in prehistoric times, because human beings were still mating with each other all across the board. Still it is ironic, given the fact that humanity might not be where it is today, if we were “pure”

4 lostlakehiker  Oct 23, 2014 1:22:37pm

re: #1 freetoken

I don’t know what the author is trying to get at here:
BEGIN QUOTE WITHIN QUOTE…While these near-eastern humans were anatomically modern, they did not show modern behaviour, he says….END QUOTE WITHIN QUOTE
I’m not sure that has been communicated clearly.

There’s this distinction between “anatomically modern humans”, whose skeletons show modern features, and “behaviorally modern”. There was an interval of several tens of thousands of years during which anatomically modern humans didn’t have anything like the sophisticated behavioral suites of later tribal societies. (That the early anatomically modern humans had such skills, but all the evidence everywhere was lost, seems improbable in the extreme.) Today, or 1000 years ago, and from what evidence we have, 40 000 years ago or more, these not-so-primitive-after-all societies, across the globe, featured decorative and technological feats not evident in the record of the earlier anatomically modern humans.

One of the most interesting things about the new find has to do with the way the Neanderthal DNA was arranged on the chromosomes. When sperm and egg meet to form the zygote, very long stretches of the DNA of each parent are present in the genome of the offspring. Over time, these long stretches tend to get chopped up, as the mixmaster of reproduction churns up new combinations. When different species crossbreed, (and not just then, but no need to go into the rest of the story here) we can see from the length of the fragments how long it’s been since the crossbreeding. Today, Neanderthal components of the human genome appear in short bits and pieces here and there. In this find, the components appear in considerably longer chains, which indicates that the mixing hadn’t yet become a thing of the distant past. And that points to the conclusion that the intermixing occurred during the era of behaviorally modern humans. And fairly late on, really.

5 lostlakehiker  Oct 23, 2014 1:34:58pm

re: #3 CriticalDragon1177

Actually from what I understand Neanderthal genes did end up in sub Saharan African populations in prehistoric times, because human beings were still mating with each other all across the board. Still it is ironic, given the fact that humanity might not be where it is today, if we were “pure”

You’re saying “New Scientist” got it wrong? Interbreeding doesn’t always carry a small genetic contribution from “outside” into the fixed genome of a partially isolated population. It depends on whether the gene that is introduced confers some selective advantage. The probability that the gene will become fixed in its new population, despite having been introduced just a handful of times, is near zero if it confers only a small advantage, and is effectively zero if it is neutral.

We may reasonably speculate that the Neanderthal genes that did go to fixation in the outside-Africa population conferred some advantage that was local to outside-Africa, such as resistance to diseases found outside Africa, or resistance to cold. Or they were neutral, and got carried along for the ride by genes that did confer an advantage.

As to purity, it’s way overrated. Humans, and not just humans, are so “impure” as to incorporate in their genome fragments of virus DNA. DNA from vessels so far on the evolutionary tree from ourselves that it’s hard to find anything farther.

And we’re built to be attracted to exotic mates. The tall, dark, handsome stranger. The mysterious woman. Etc. Stock figures from literature are stock for a reason: outbreeding (within the species, and it seems, even a bit outside that fairly wide perimeter) pays.

6 CriticalDragon1177  Oct 23, 2014 1:45:25pm

re: #5 lostlakehiker

You’re saying “New Scientist” got it wrong? Interbreeding doesn’t always carry a small genetic contribution from “outside” into the fixed genome of a partially isolated population. It depends on whether the gene that is introduced confers some selective advantage. The probability that the gene will become fixed in its new population, despite having been introduced just a handful of times, is near zero if it confers only a small advantage, and is effectively zero if it is neutral.

We may reasonably speculate that the Neanderthal genes that did go to fixation in the outside-Africa population conferred some advantage that was local to outside-Africa, such as resistance to diseases found outside Africa, or resistance to cold. Or they were neutral, and got carried along for the ride by genes that did confer an advantage.

As to purity, it’s way overrated. Humans, and not just humans, are so “impure” as to incorporate in their genome fragments of virus DNA. DNA from vessels so far on the evolutionary tree from ourselves that it’s hard to find anything farther.

And we’re built to be attracted to exotic mates. The tall, dark, handsome stranger. The mysterious woman. Etc. Stock figures from literature are stock for a reason: outbreeding (within the species, and it seems, even a bit outside that fairly wide perimeter) pays.

No I didn’t say they got it wrong. No one group of modern humans were ever totally isolated. You don’t think that one person would make with another person, and than that other person mate with another person in a slightly different location, and than that person’s son or daughter mate with another person in a different location, and so on?


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