[ExI] Fermi Paradox and GRB bursts
anders at aleph.se
Mon Oct 6 09:44:50 UTC 2014
Dan <danust2012 at gmail.com> , 3/10/2014 9:34 PM:
On Friday, October 3, 2014 11:37 AM, BillK <pharos at gmail.com> wrote:Evolution could be postponed for millions of years.
That would depend on many factors, but my qualitative non-expert view is more than millions, but tens of millions of years to recover, depending on those other factors.
I looked a bit at this for a paper. The references I found suggested that it took 5-30 million years after the end-Permian extinction for the biosphere to recover. Ecosystems bootstrapped faster, but most were simple and cosmopolitan - essentially weed ecosystems. It looks like the evolutionary radiation into new niches takes at least 5 million years, possibly longer.
Sahney S, Benton MJ. Recovery from the most profound mass extinction of all time. Procedings of the Royal Society B, 2008; 275: 759–765.http://rspb.royalsocietypublishing.org/content/275/1636/759.full.pdf+html
Douglas H Erwin. The end and the beginning: recoveries from mass extinctions. Trends in Ecology & Evolution. Volume 13, Issue 9, 1 September 1998, Pages 344–349http://www.sciencedirect.com/science/article/pii/S0169534798014360
Note that this does not put a huge dent in the evolution of intelligence. It took 5 million years from the common ancestors of chimps and humans to us. I think the bigger problem is the Lilliputian issue: survivor species tend to be small, and if it takes a certain body size for intelligence (large animals are metabolically more efficient due to allometric scaling, so they can more easily afford big brains) then there is going to be a delay until they get large enough. But I would not think the probability of intelligence 15 myr after a mass extinction is vastly lower than just before (5 myr of recovery, 5 myr of size scaling, 5 myr of potential intelligence scaling).
Anders Sandberg, Future of Humanity Institute Philosophy Faculty of Oxford University
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