> I was wondering if anyone has retrieved ancient DNA from amber insects or
> wooly mammaths or any old sources? Is this even possible? If some has been
> looked over what have we found that relates to evolution or maybe even the
> molecular clok rates.
Dave Tyler responding:
"Yes. This has been done and it has yielded much controversy. Some now
think that all DNA from amber is contamination - but this is by no means
agreed. A 1993 article pointing out the implications if the DNA is
genuinely present in these fossils is at:
http://www.pages.org/bcs/Bcs041.html Fossil DNA in amber and implications
for geological time."
The implications of that article are that DNA cannot last more than 10,000
years (40,000 at the outside), so if DNA is found in bones or insects
trapped in amber then the bones or insects must be at least 10,000 years old
and certainly no older than 40,000 years old, in the absence of a credible
explanation for how DNA can be preserved for millions of years.
I did a literature search last night using the Entrez MedLine database at
<http://www.ncbi.nlm.nih.gov/Entrez/medline.html>. I found not only the
review articles I reported to Andrew, but more. The current concensus
appears to be that in fact DNA cannot survive millions of years even in
amber [Austin JJ, Ross AJ, Smith AB, Fortey RA, Thomas RH. "Problems of
reproducibility--does geologically ancient DNA survive in amber-preserved
insects?" _Proc R Soc Lond B Biol Sci_ (1997) 264:1381, 467-474]. However,
new techniques have extended the age range for acquiring DNA from bone out
to 15,000 years and there are both handling techniques and tests that insure
that the samples are not contaminated. Ancient DNA analysis is now a
standard tool in molecular evolution for all samples less than 15,000 years
old. The recent recovery of DNA from Neandertal bones could push the
technique to even older ages. Given time, we might eventually be able to
acquire DNA from bones and teeth that are at least 100,000 years old, maybe
even a million. Whether we can go still farther back in age remains to be
seen.
Even so, for now at least, the implications reported on in the article Dave
cited are largely moot. There has been no unambiguous recovery of DNA from
any sample a million years old or older.
Kevin L. O'Brien