Genetic Bottleneck

21 June 2018

This one was sent in by Jovan – go to …. males genes across Asia, Europe and Africa seem to suggest something peculiar happened between 5000 and 7000 years ago (or 3000-5000BC) in which women were left numbering 17 to 1. Obviously, this can't be strictly true unless it was a mutation of some kind (lucky fellas if that was the case). The idea of a male bottleneck at this point in time was first raised by researchers in 2015 and since then scientists have been trying to make sense of it all. Were male members of hunter gatherer groups killed off and the women seized as trophies, is one idea that has been touted. What about an epidemic that affected men but not women – doubtful. What other factors are true of men but not of women (in a general sense). The writers of the latest paper suggest that endemic warfare played a role – a role usually undertaken by men (or that is the assumption).

However, was there really a drastic drop in male numbers. A population geneticist at Stanford University claims otherwise. The diversity of the Y chromosome decreaed due to the way people fought each other. There was actually fewer males – just less diversity amongst the males. In addition, dominant warriors may have dominated the surviving genes.

This is an interesting point in history as there were a succession of catastrophic events – at 4300, 3200, and 2345BC (for example) and possibly more as something was setting people in motion – even farmers that had set down roots. Hence, the period involves a lot of migration events – especially in Europe and Asia (and no doubt in Africa as well). As such, a simplistic picture of the period is not possible – and to say it was all down to clan warfare is being a bit optimistic, we might say.

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