Who's your daddy? Not this mummy, DNA tests reveal

Researchers have mapped the mitochondrial genome of one of the world's oldest mummies, discovering in the process a genetic lineage that does not match any of those known to exist today.

The Tyrolean Iceman, or tzi, is a mummified corpse more than 5,000 years old recovered from an Alpine glacier on the Austro-Italian border in 1991.

In 2000, scientists defrosted the Iceman's body and sampled mitochondrial DNA from his intestines.

Mitochondrial DNA is found outside the nucleus in the mitochondria, where a cell generates energy. Since cells can contain thousands of mitochondria, mitochondrial DNA is more plentiful than nuclear DNA and easier to recover. Mitochondrial DNA can come from hair shafts or bone cells lacking a nucleus, or from smaller, older fragments of evidence.

The original examination of the Iceman's DNA found that he belonged to a lineage known as the K1 subhaplogroup, one shared byeight per cent of modern Europeans.

However, a more detailed study of the genome, published Thursday in the journal Current Biology, found that the Iceman's genome did not match any of the known subgroups of the K1 group.

"Through the analysis of a complete mitochondrial genome in a particularly well-preserved human, 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," said Franco Rollo of the University of Camerino in Italy one of the authors of the study.

The researchers have informally named the newly discovered branch on the human family tree "tzis branch."

"Apparently, this genetic group is no longer present," said Rollo in a statement. "We dont know whether it is extinct or it has become extremely rare."