[ExI] homo sapiens as endangered species

Stefano Vaj stefano.vaj at gmail.com
Fri Jun 3 11:41:40 UTC 2011

On 2 June 2011 21:33, Anders Sandberg <anders at aleph.se> wrote:

> Low genetic diversity is less of an issue than many think (but it
> contributes a bit). The real threat is demographic noise: a small population
> will have larger relative fluctuations, some of which can drive it down to
> even smaller and even more vulnerable. A species "circling the drain" can
> run into problems both with bad years, with few children due to bad luck,
> bad luck with gender ratios, Allee effects and a bunch of other things.
> In my sims I need about 2000 people to get long term survival with more
> than 90% probability. Smaller populations can survive, but they need to be
> lucky.


OTOH, speciation happens exactly out of the genetic drift which in principle
affects the smallest, and reproductively most segregated, populations. In
turn, diversity arises again in the new species as a consequence of
mutations and selective pressures acting on larger numbers as soon as they
can be re-established.

Let us just say that the seed has to be very lucky to become a tree.

Stefano Vaj
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