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Re: theP-T boundary
Ron Dass <firstname.lastname@example.org> wrote
> On the other hand, most estimates I've seen say about 95% of all
>species checked out at the end of the Permian.
Have you seen most "estimates" of 95% or most "quotes" of that figure ?
If I may quote from David M Raup, Extinction: Bad Genes or Bad Luck ?,
OUP, 1993, pp 72-74
"Many readers will have heard that 96 percent of all species living near the
of the Permian were killed in the big mass extinction at that time. This number
comes from the reverse rarefaction graph of Figure 4.2. This estimate is
probably an exaggeration, because the extinction of species is not completely
random. If extinction is focused on certain genera and families, killing will
concentrated in these groups. If reverse rarefaction is used to estimate
species kill from the extinction rates of genera or families, any departure
random (Field of Bullets) killing will exaggerate species kill.
I am slightly embarrassed by the wide use of the figure of 96 percent for the
Permian because I was responsible for it in a 1979 article presenting the
reverse-rarefaction method. Although my article contained ample caveats
about the random-killing assumption and although I said that the 96 percent
estimate was an upper limit, all too many users of the number have neglected
to mention the caveats. In truth, I probably did not exert myself to emphasize
The article Raup referred to : Raup D M, Size of the Permo-Triassic
bottleneck and its evolutionary implications, Science 1979; 206: 217-18.
In this Raup actually gave a range of 80-96% species extinction.
Alper gave somewhat lower figures : Land animals 80%, Marine animals
probably over 90% (Alper J, Earth's near-death experience, Earth (January)
1994; 3 (1): 42-51) though he had not cited any primary source.
I have not seen any other estimate which specified the 95/96% extinction of
species at P-T boundary. Is there any other published estimate (not citing
Raup) which independently came to such a high figure ?
Gautam Majumdar email@example.com