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Re: Selective Extinction



Michael said:

>There is some good evidence to suspect that Bovine Immunodeficiency Virus
>(BIV) infected cats ?5-10mya resulting in Feline Immunodeficiency Virus

I'm not even going to *ask* how a sexually transmitted disease got from cows
to cats!  Lions lying down with lambs?

>So we have at present a virus that spread from Family to Family eventually
>becoming a pathogen.  Whether this happened to dinosaurs or not is
>speculation.

I'm not seriously suggesting it at the KT.  However, its an open question
for other, earlier extinctions.  What's most interesting about your
observation is the suggestion that FIV hits all felines, providing a
potential mechanism to affect a whole family without regard to ecological
niche.  Did I understand this correctly or did you just mean lions?

>inbreeding such as todays cheetah.  However, IMO, a pathogen would be
>unlikely to kill an entire class or order.  I can't think of a model but
>then we haven't known about pathogens very long either. 

Obviously such a pathogen would not survive.  On the other hand, neither
would its hosts, thus leading to mass extinctions presumably of both
pathogen and host. Virulence factors for viruses often (I understand) turn
out to be genes native to the host,  whether latent helper viruses or
actually functioning genes.  Clearly there's a better chance of those
sequences being shared among related organisms.

On the other hand, I can't think of a way to test any of this except by
statistical analysis of extinctions which can't be otherwise explained.  I
doubt the fossil data is good enough to do this kind of analysis in most
cases.  (Elizabeth Vrba's antelopes maybe?)

  --Toby White