Did Neanderthal cells cook as the climate warmed?

Neanderthals may have gone extinct because their cells couldn't cope with climate change, according to a new hypothesis presented at a genetics conference this month.

Metabolic adaptations to Ice Age Europe may have proved costly to Neanderthals after the continent's climate started to change, says Patrick Chinnery, a molecular biologist at Newcastle University, UK.

He and colleague Gavin Hudson identified potentially harmful mutations in the newly sequenced Neanderthal mitochondrial genome. In particular, the researchers found genes that are associated with neurodegenerative diseases and deafness. "If they were found in modern humans they would be bad news," Chinnery says.

The extinction of Neanderthals, close relatives of modern humans, some 25,000 years ago remains unexplained.

One theory holds that they were physically outcompeted by modern humans , another that they were economically eclipsed by us.. Yet another theory suggests that Neanderthals couldn't adapt to climate change.

The discovery of harmful mutations in the Neanderthal mitochondrial genome supports the climate-change idea, with a twist.

Chinnery and Hudson suggest that mutations in mitochondria helped Neanderthals cope with the cold weather, but that when the climate started fluctuating between warm and cold periods, they were at a disadvantage.

In all cells, from yeast to human, a mitochondrion's main job is to produce the energy that powers cells - this takes the form of a chemical called ATP. Our mitochondria do this quite efficiently under ideal conditions, making 36 ATP molecules with the energy stored in a single molecule of glucose sugar.

Mutations that sap this efficiency would generate heat instead - a potentially useful trick for Neanderthals who are known to have had adaptations to cold weather, Chinnery says. However, a warmer and less climatically stable habitat could have spelled trouble for Neanderthals with such mutations. .... However, with only a single Neanderthal DNA sequence decoded so far, that hypothesis remains provisional. ... - newsci