In article <EDDY.95Oct7085053 at wol.wustl.edu>,
Sean Eddy <eddy at wol.wustl.edu> wrote:
>>This is no problem, so long as the origin of life is probable, or the
>Earth was lucky. But if it turns our that there just has to be a few
>billion years for a massively complex life form like the last common
>ancestor of Earth life to arise, it might become necessary to explore
>the possibility that life arose on another, older world.
>>Not that the hypothesis is testable, mind you.
Of course it is!!!! There are a number of proteins (glutamate
dehydrogenase is perhaps the best candidate) with rates of change that
allow us to look back much longer than 10By, the putative age of the
%A R. F. Doolittle
%A D. F. Feng
%A M. S. Johnson
%A M. A. McClure
%J Cold Spring Harb. Symp. Quant. Biol.
%T Relationships of human protein sequences to those of other organisms
All we have to do is sample a life form from outer space, and the
question could be answered quite quickly (I would be convinced if they
had the same 20 amino acids I think).
wrp at virginia.EDU
Dept. of Biochemistry #440
U. of Virginia
Charlottesville, VA 22908