[ExI] homo sapiens as endangered species

[Anders Sandberg]

Stefano Vaj wrote:
> On 2 June 2011 18:58, Anders Sandberg <anders at aleph.se 
> <mailto:anders at aleph.se>> wrote:
>
>     When I saw the subject of this thread I thought it was more about
>     xrisks. I have been tinkering with some minimum viable population
>     models of H. sapiens. If we are ever near extinction, it is pretty
>     tough to maintain a population - big mammals are tricky.
>
>
> I have some vague recollection of this notion, but do not remember the 
> reasoning behind it.
>
> Why a few fertile individuals are actually not enough?

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.

-- 
Anders Sandberg,
Future of Humanity Institute
Philosophy Faculty of Oxford University