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I don't think it matters much the "small subset of human genes left Africa". More crucial is that the African landscape is quite varied and not too harsh. Almos

by has2k1 10y ago

I don't think it matters much the "small subset of human genes left Africa". More crucial is that the African landscape is quite varied and not too harsh. Almost everywhere south of the Sahara a small tribe could eke out a living. And yet, the environment wasn't too friendly to readily encourage population growth that lead to civilisation(s). Such forces lead to genetic drift (and therefore variation) and also makes tribal formations unavoidable. The phenotype(s) of these tribes are then the embodiment of that genetic drift. When it comes to height, you end up with the Pygmy tribes in the Congo basin and the Dinka along the Nile basin.

riffraff 10y ago
IIRC Australian aborigines, Europeans, and native Americans share most of their DNA, this is across many different landscapes and chances for isolation. Also, civilizations are quite recent compared to the length of the genetic drift.
deleted 10y ago
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tomp 10y ago
> And yet, the environment wasn't too friendly to readily encourage population growth that lead to civilisation(s). Hm... maybe the environment was too friendly to encourage a civilisation? I mean, if food grows around you all year long, you're much less inclined to develop means of storing it than if you know you'll experience harsh winter in a few months... Same with housing, clothing, heating, etc.
- has2k1 10y ago
  I think you are not considering that before the domestication of plants, even if "food was growing around you all year long", it had low caloric content. The key measure is the cost of getting them calories. There are rough thresholds that almost guarantee that you may forever survive but never thrive.
dnautics 10y ago
> I don't think it matters much the "small subset of human genes left Africa". That is exactly wrong. Bottlenecking is the reason why diversity outside of africa is dramatically lower than the within the continent. http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1003309 http://journals.plos.org/plosgenetics/article?id=10.1371/jou... "The pattern of genomic variation in contemporary southern African populations thus resulted from unions between the most diverse genomes found within Africa to the least differentiated as represented by populations impacted by a severe founder effect (bottleneck) associated with the out-of-Africa dispersal"
- has2k1 10y ago
  Given time, a hash enough environment is going to select for phenotypes despite the quality of the genetic variation. That has to happen or the group dies off [1]. That is the point of the phase "I don't think it matters much". I expect a refutation of that statement to be along the lines of, "here is information that shows that the difference in genetic variation between the in Africa and outside of Africa peoples is so big (or the latter have very low variation) that there are marked differences in adaptability to different environments". [1] The reason for extinction may well be very low genetic variation.

by has2k1 10y ago

riffraff 10y ago

IIRC Australian aborigines, Europeans, and native Americans share most of their DNA, this is across many different landscapes and chances for isolation. Also, civilizations are quite recent compared to the length of the genetic drift.

deleted 10y ago

[deleted]

tomp 10y ago

> And yet, the environment wasn't too friendly to readily encourage population growth that lead to civilisation(s). Hm... maybe the environment was too friendly to encourage a civilisation? I mean, if food grows around you all year long, you're much less inclined to develop means of storing it than if you know you'll experience harsh winter in a few months... Same with housing, clothing, heating, etc.

has2k1 10y ago
I think you are not considering that before the domestication of plants, even if "food was growing around you all year long", it had low caloric content. The key measure is the cost of getting them calories. There are rough thresholds that almost guarantee that you may forever survive but never thrive.

dnautics 10y ago

> I don't think it matters much the "small subset of human genes left Africa". That is exactly wrong. Bottlenecking is the reason why diversity outside of africa is dramatically lower than the within the continent. http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1003309 http://journals.plos.org/plosgenetics/article?id=10.1371/jou... "The pattern of genomic variation in contemporary southern African populations thus resulted from unions between the most diverse genomes found within Africa to the least differentiated as represented by populations impacted by a severe founder effect (bottleneck) associated with the out-of-Africa dispersal"

has2k1 10y ago
Given time, a hash enough environment is going to select for phenotypes despite the quality of the genetic variation. That has to happen or the group dies off [1]. That is the point of the phase "I don't think it matters much". I expect a refutation of that statement to be along the lines of, "here is information that shows that the difference in genetic variation between the in Africa and outside of Africa peoples is so big (or the latter have very low variation) that there are marked differences in adaptability to different environments". [1] The reason for extinction may well be very low genetic variation.