The Neanderthals stand as the most famous example of a rival group of humans, evolutionary cousins who were wiped out by the expansion of our ancestors. But now it looks like Neanderthals were doomed long before ancient (modern) humans showed up.
Our ancestors reached Europe, the main domain of the Neanderthals, about 40,000 years ago. The consensus view had been that Neanderthals dominated this continent, and that the arrival of modern humans - whether through warfare, disease, interbreeding, or simply being beaten out for control of resources - is what made Neanderthals disappear by about 30,000 years ago.
But a team of Spanish and Swedish researchers say that new DNA evidence paints a far grimmer view of the state of Neanderthals. Their analysis suggests the Neanderthal population had crashed 50,000 years ago, and a relatively small band of survivors then recolonized central and western Europe before their final end 20,000 years later. In a statement, Love Dalén of the Swedish Museum of Natural History explained what they discovered:
"The fact that Neanderthals in Europe were nearly extinct, but then recovered, and that all this took place long before they came into contact with modern humans came as a complete surprise to us. This indicates that the Neanderthals may have been more sensitive to the dramatic climate changes that took place in the last Ice Age than was previously thought."
The key here, according to the researchers, is the fact that the genetic variation in later Neanderthal fossils found in Northern Spain is extremely limited, which is indicative of a tiny population. Uppsala University's Anders Götherström gives a sense of just how bad the situation had become for the Neanderthals by the time humans showed up:
"The amount of genetic variation in geologically older Neanderthals as well as in Asian Neanderthals was just as great as in modern humans as a species, whereas the variation among later European Neanderthals was not even as high as that of modern humans in Iceland."
The team is working from severely degraded DNA, but they have enough samples - and analysis techniques have improved enough in recent years - that they feel confident the picture they've drawn is accurate. If true, it would seem the brutal European climate did the dirty work of getting rid of some of our most recent competitors. This also raises the question of just how humans would have really fared against a Neanderthal population at full strength. I'm sensing some pretty serious alternate history fodder here...