快猫短视频

CONTROVERSY over the identities of the bones of ancient human ancestors could
soon be resolved by a remarkably simple, low-tech method of DNA analysis
developed by an international team of researchers.

Lutz Bachmann, an evolutionary geneticist at the Field Museum in Chicago,
Illinois, and his colleagues in Britain and Germany have adapted a standard
technique called Southern blot hybridisation to rapidly distinguish between
ancient Homo sapiens and Neanderthal remains. 鈥淲hen we told people we
were trying this they said we must be joking,鈥� says Bachmann. 鈥淏ut it turns out
to work surprisingly well.鈥�

Two previous attempts to analyse DNA from Neanderthal skeletons, the latest
reported only two months ago in Nature, rely on the highly sensitive
polymerase chain reaction (PCR) technique. This uses enzymes to make millions of
copies of the DNA sequences from the shattered genetic remains found in ancient bones
(快猫短视频, 19 July 1997, p 5).

The very power of PCR means that researchers have to be extremely careful not
to contaminate the sample with their own DNA. So Bachmann and his colleagues
wondered if they could develop a technique suitable for the routine analysis of
samples. They settled on a variation of the Southern blot, one of the first DNA
techniques developed.

This type of analysis exploits a particular property of DNA. Genetic
sequences from one animal stick to, or 鈥渉ybridise鈥�, better with DNA from a
member of its own species than the DNA of another species. This allows
researchers to identify DNA directly, without amplification. However, it wasn鈥檛
clear how reliable these blots would be for the highly degraded DNA typical of
fossilised bone.

So Bachmann鈥檚 team tested the blotting technique on two samples of DNA
extracted from Neanderthal bones, a sample of ancient H. sapiens DNA
and genetic material from other mammals. They found the method could easily
distinguish between the sources of the DNA. For example, the two Neanderthal DNA
samples hybridised twice as well to each other as they did to the ancient H.
sapiens sample. Contemporary human DNA hybridised more than four times as
well to ancient H. sapiens DNA as to Neanderthal DNA. The hominid DNAs
showed no affinity for ancient DNA from reindeer and woolly mammoths.

鈥淲here there is ambiguity about a sample鈥檚 classification, this could be of
the highest interest,鈥� says anthropologist Ian Tattersall of the Museum of
Natural History in New York. He says the technique seems like a promising way to
make quick and dirty molecular comparisons. But Milford Wolpoff of the
University of Michigan at Ann Arbor worries about concluding anything from so
few samples. 鈥淭his is a very crude technique at best.鈥�

鈥淚鈥檇 be very happy to put the method to the test again and again,鈥� says
Bachmann. 鈥淚 just need more samples.鈥�