it's overly simplistic to point entirely at climate change. and, in fact this is a revisionist understanding of things with a huge political motive underlying it. certain academics find the idea of tribes fighting each other to extinction to be distasteful - despite overwhelming evidence in the historical period.

i predict that a thousand years from now the same sort of academics will argue that the native americans were destroyed by climate change because they don't like the idea of genocide. it's too divisive. racist, even.

the reality is that genocide is a constant in recorded history, and to deny it existed in pre-history is nothing short of delusional.

further, climate change often works better together with genocide than it does as a contrary hypothesis to it. the southern movements of tribes in the historical period often had to do with the weather changing. there are clear destruction horizons in the indus valley that almost certainly had to do with iranian tribes moving southward, which brought their language and their religion into india and iran. this seems to have to do with the temperatures decreasing around the caspian.

the civilizations of the fertile crescent sucked at doing irrigation, and that remains a gigantic problem in the region to this day.

there are documented migrations from central asia into greece during the period that the minoans disappeared, including the replacement of the indigenous language with the greek one.

greenland is a good example, but it also had to do with the country's extreme isolation.

but the takeaway is the climate change leads to migration, rather than collapse, and that migration has historically had incredibly disruptive consequences. we may like to think we're beyond that, or that our guns are big enough to counteract it. but maybe that's a little naive, too.

http://energyskeptic.com/2013/climate-change-has-destroyed-many-civilizations-in-the-past/

what a lot of the studies you'll see about this will do is build up this strawman about race, knock it down and then claim it proves something.

you don't need to talk about prehistoric migrations to get an understanding of gene flow between the middle east and central asia, or between india and china. there have been huge trade networks across these region for as long as time has existed, and slave trades working in all directions. it only makes sense to say "we didn't find evidence of a racial marker" if you begin with the argument that races exist in the first place; if you acknowledge that races actually don't exist, and almost all markers exist in almost all populations at different frequencies, none of the evidence is relevant to the question.

what follows is that you cannot use genetic evidence to demonstrate anything other than that there's no such thing as race in the first place.

now, as for various mutations, finding high frequencies indicates migration paths, yes. but it's beyond specious to try and connect those ideas to this archaic fabrication of a concept that is race.

that means that it's entirely consistent to pull most genetic diversity in india from an indigenous root AND accept the invasion hypothesis, and that proving the local nature of that diversity does NOT disprove the idea of a southern invasion.

if you look at the historical period, we can see invasions that have had dominant effects on the genetic and cultural make-up of the population (arab invasion of north africa), that have led to mixed peoples with mixed cultures (turkish invasion of anatolia) or that have left a culture with little genetic influence (bolivia is a good example, as would be most of colonized africa).

i mean, do you take a genetic sample of french-speaking, christian central africans and use it to disprove french colonialism?

i'd hazard an educated guess that there's more african dna in europe than there is european dna in africa.

this hippie whitewashing of history will be reversed, along with everything else they've fucked up. it's just unfortunate to have to live in this period, where truth is a constant casualty to orwell.