In Article <7MAY94.04423854 at biotek.arc.ab.ca>, matlock at biotek.arc.ab.ca wrote:
> Does anyone know where I could find more information about fossil DNA or
>genetics? Eventually, I need to consider the following question bothering
>me and a few friends:
>> I use the definition that two animals are of the same species if they can
>naturally mate and produce fertile offspring.
>> How far back in time can we go before a species can no longer mate with
>its ancestors. This is obviously a hypothetical question, since ancestral
>species are usually extinct. But say we had genetic samples of homo habilis.
>Can we compare their genes with ours and come to any conclusions about our
>mating compatibility? I need to know where to look to find out if anyone
>has done any work along these lines.
>> I think paleontologists don't use the above species definition, since
>they can only compare morphological or environmental characters.
>> Please email your answers, as well as post if you think you should.
The only information on molecular data from fossils that I am aware of are a
few reports on collagen from bones and some of the DNA extracted from
amber-embedded organisms. I think that we will never have sufficient DNA
sequence from fossils to answer the question you are after. For one thing,
an early biological determinant of mating incompatibility is probably
changes in chromosome structure, which will interfere with functional
meiosis. To see that, you would need a full karyotype analysis; I think
that is extremely unlikely. Most of the structural genes are not going to
confer mating incompatibility.
Paleontologists go with morphological definitions of species because that
is what their data will allow them. I wish we could get the data that
you're suggesting, but I think it is in the realm of science fiction right now.
Department of Zoology, University of Alberta
wgallin at gpu.srv.ualberta.ca