The eyes had it

Too much visual knowledge can be a dangerous thing, if you're a neanderthal;

A study of Neanderthal skulls suggests that they became extinct because they had larger eyes than our species.

As a result, more of their brains were devoted to seeing in the long, dark nights in Europe, at the expense of high-level processing.

By contrast, the larger frontal brain regions of Homo sapiens led to the fashioning of warmer clothes and the development of larger social networksA study of Neanderthal skulls suggests that they became extinct because they had larger eyes than our species.

The study is published in Proceedings of the Royal Society B.

Or, perhaps, their eyes were bigger than their stomachs.