The so-called Tyrolean Iceman, a 5,000-year-old mummy found in an Alpine glacier roughly two decades ago, lived in an era when people were smelting copper and living in cities. But a recent study of his mitochondrial DNA — circlets of genetic material passed on solely through mothers — revealed something astonishing about this recent human ancestor. He is from a distinct genetic group that mysteriously disappeared. Perhaps no one sharing his genetic lineage survived into the present day. Or perhaps humans are evolving so quickly that even our close ancestors are genetically distinct from us in significant ways. When Tyrolean Iceman was defrosted in 2000, researchers took some DNA from his intestines and sequenced it. But that was only his nuclear DNA, inherited from both parents, and it revealed that he was related to a large group of Europeans who share a common ancestor. The new study, which will be published November 11 in Current Biology, allowed researchers to examine the mummy's lineage in more detail. And that's when they realized how different he was from modern populations. Said Franco Rollo, a co-author of the study:
We have obtained evidence of a significant genetic difference between present-day Europeans and a representative prehistoric human—despite the fact that the Iceman is not so old—just about 5,000 years. This doesn't simply mean that Ötzi had some 'personal' mutations making him different from the others but that, in the past, there was a group—a branch of the phylogenetic tree—of men and women sharing the same mitochondrial DNA. Apparently, this genetic group is no longer present. We don't know whether it is extinct or it has become extremely rare.
What this reveals is that even large groups of genetically similar people can completely disappear from the gene pool in a relatively short time. This should shore up current theories that hold humans are actually evolving very rapidly. SOURCE: The Complete Mitochondrial Genome Sequence of the Tyrolean Iceman [via Current Biology]