Important Discoveries of 2008 - Mammoths: Hitting a Genetic Wall?

[image]

(Petr Novák, Wikipedia)

New techniques for analyzing ancient DNA are helping scientists understand the evolution of the woolly mammoth and why these relatives of modern day elephants went extinct around 10,000 years ago. Paleolithic humans have often been blamed for hunting mammoths to extinction. The DNA studies, however, reveal that the cold-adapted elephants had very little genetic diversity, which may have made the species susceptible to being wiped out by disease.

Based on a study that compared the mitochondrial DNA (genetic material from the organelles that provide cells with their energy) of 18 mammoths and a separate research project that has assembled 70 percent of the mammoth genome, Stephan Schuster a genomicist at Pennsylvania State University, a co-author on both studies, believes that several factors including a changing climate led to the species' demise. "The weather getting a little bit warmer can make a huge difference in humidity, and more humidity means more snow, then, animals can't find food anymore." He says," A little bit warmer summer can also mean a much higher pathogen [disease] load." Schuster doesn't let Paleolithic hunters off the hook entirely. He acknowledges that additional pressure from hunting could have been enough to finish off the last of the mammoths.

The techniques that the research team to which Schuster belongs used may revolutionize the study of ancient DNA. Previous studies of genetic material from extinct species relied on samples taken from bone, which yielded samples that were heavily contaminated with DNA from fungus and microbes. The new study used a DNA sample taken from inside the shaft of a hair, which was 90 percent pure and much easier to analyze. The research team is still at work sequencing the last 30 percent of the mammoth genome, raising the possibility of cloning a mammoth from ancient DNA. "It is not what is really driving our science," says Schuster, "but everybody agrees that it is no longer impossible."

More Top Discoveries of 2008