Wednesday, 13 November 2013

The Neanderthal Within: The Science of Cousin-Lovin’

One of the most interesting facts in the study of human evolution is that for a very long stretch of time (much longer than modern humans have existed) there were multiple species of humans running around the planet trying to make their way. We (Homo sapiens sapiens) represent the only surviving species on the branch on the tree of life known as Homo.

So what happened to the others? There are too many stories to tell in such a short article but one stands out as being worth sharing. It is the story of our closest cousins. A group with whom we shared the planet for roughly 160,000 years before they vanished about 40,000 years ago. Today we call them Neanderthals (Homo neanderthalensis).

In the same way that people are often hard on their relatives, modern culture has been tough on Neanderthals. We tend to think of them as prototypical cave-people. Hunched over, heavy brows, probably carrying a club, and dumb as a rock. The problem with the Fred Flinstone view is that the evidence contradicts it pretty badly.

The more Neanderthal skeletons we look at and the more sites we examine, the more scientists are realizing that Neanderthals were the equal of their H. sapiens counterparts. In a lot of ways, they even had us bested. First and foremost, they were physically stronger. They were slightly  shorter than modern humans with males reaching an average height of about 5 foot 6 inches and females just a touch over 5 feet tall, but their bone structure suggests that they were more heavily muscled and the injuries they routinely survived imply that they were tough as nails.

That is pretty unsurprising. You would expect a species of human that lived in Europe during an ice age to be pretty tough. The second fundamental difference between our species hits a little closer to the modern human ego. Neanderthals may have been smarter than us.

Not only did the average Neanderthal have a larger brain than a modern human, they also left behind evidence of art and advanced tool making abilities. Some scientists have even suggested that modern humans stoleideas from Neanderthals when it can to making spear points and the like.

Clearly something isn’t adding up here. If Neanderthals were stronger, smarter, and more technologically advanced than us, why aren’t they around today? There are a couple explanations. First, brain size isn’t everything. Recent research has suggested that a greater portion of a Neanderthal’s brain was devoted to processing vision and movement and less was devoted to social networking compared to modern humans. Second, when you factor in brain to body mass ratio, modern humans aren’t left as far behind.

The difference in technology can be explained by necessity. Modern humans evolved in conditions that were less demanding than Neanderthals. While they were chasing mammoths through blizzards, we were running around in the warm climes of Africa. We had a lot of the same problems to solve, but they had more of them overall.

Eventually when humans showed up in Europe we managed to overtake Neanderthals in terms of population. It may have been luck, or it may have been ingenuity. What is incontestable is that we edged them out, but we may have not wiped them out. Recent analysis of Neanderthal DNA and comparisons with our own genetic code strongly suggest that once we had them outnumbered, we began absorbing them through interbreeding.

That is one of the great things about science. Just when you think you have things figured out, you get an M. Night Shyamalan  twist that leaves you questioning your whole perception of things. It becomes a lot harder to think of Neanderthals as club-carrying knuckle-draggers when you find out that the DNA of your average person of European descent is 2.5% Neanderthal.

It looks like the branches on the tree of life are bit more tangled up than we originally thought.

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