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Antique DNA

Dateline: 07/20/98

By Alan Bruzel

Sequence comparisons of deoxyribonucleic acid (DNA) can reveal the genetic relationships of living species to their remote ancestors. The samples must contain regions of uninterrupted and chemically unmodified DNA for these comparisons to be meaningful. Highly degraded material will not yield useable sequence; DNA needs to be extracted from well-preserved specimens. Published DNA analyses from 25 to 125 million-year-old amber-entrapped insects have initiated efforts to duplicate these results. DNA from dinosaur bone marrow cells is also under study. Examination of DNA from samples that are thousands, not millions, of years old encounters less skepticism. A recent example is the analysis of the extinct ground sloth, Mylodon darwinii.

There is good correspondence between segments of DNA from the Stone Age man trapped in a Tyrolean glacier 5,000 years ago and DNA from today's inhabitants of northern Europe. Also, the contention that Homo heidelbergensis was the common ancestor of both Neandertal man and modern man has been strengthened by DNA analysis of a 50,000-year-old Neandertal skeleton. DNA differences between Neandertals and modern humans indicate the two species did not interbreed.

It is not always required to have fossilized remains at hand. For example, compared to other extant European populations, the Finns show homogeneity in Y chromosome and mitochondrial DNA sequences consonant with their lineage's establishment about 4,000 years ago by a small founder group. Still to be examined are DNAs from a 500-year-old sacrificed Incan female and from a group of medieval Nubian mummies.

Flesh and bone are not exclusive repositories of DNA. Investigation of DNA isolated from 20,000-year-old ground sloth dung has not only produced data about the extinct sloth Nothrotheriops shastensis, but about its vegetarian diet as well. Comparable information may be retrieved from 45,000-year-old Neandertal feces. It is too tempting to resist pointing out this work's Lagadoan antecedent (Gulliver's Travels, Part III, Chapter V).

Recommended Web resources for additional information:

Ancient DNA
Textbook with chapters examining DNA recovery and kinship analysis.

Ancient DNA Sequences
The polymerase chain reaction and its use in ancient DNA analysis.

DNA Fingerprinting
An article from this Web site describing analysis of microsatellite repeats.

References for Ancient DNA
Literature citations of methods used in ancient DNA analysis.

Timeline of Ancient DNA Discoveries
Analyses of 100-year-old quagga DNA to 125 million-year-old insect DNA.

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