How did cave people with poor eyesight survive

Why Neanderthals could think worse than us

Everything that is known so far about the brain of Homo neanderthalensis is derived from casts of the insides of fossil skulls taken from the extinct cousin of modern humans. These models show: In some respects the Neanderthal brain seems to be very similar to that of Homo sapiens. For example, both have a similar furrow structure on the surface, and both have an enlarged frontal lobe compared to the rest. But there are also differences: the Neanderthal's olfactory bulb was smaller and its parietal lobes wider and flatter.

Not just external differences

In addition, there are some indications that his brain was also structured differently internally than that of early anatomically modern humans, say the scientists. They consider two points in particular to be decisive: First, the Neanderthals had larger and stronger bodies than their contemporary Homo sapiens. As a result, the area of ​​the brain that controls the body and movements must have been significantly larger. And secondly, the Neanderthals developed primarily in Europe and thus in far less sunny climes than modern humans who had just emigrated from Africa.

Such a life in higher, less sunny latitudes, the scientists had already been able to show in earlier work, permanently changes the anatomy of the skull, at least in modern humans: the eyeballs and thus the eye sockets become larger, and the visual centers in the brain also increase in volume. They found this effect in the Neanderthals when they compared 21 fossil skulls with an age between 27,000 and 200,000 years with 38 similarly old Homo sapiens skulls: The Neanderthals had significantly larger eye sockets than their cousins ​​and must therefore, if the same connection As with Homo sapiens, they also had larger visual centers in their brains.

Without a visual center, not much is left

Now what happens if you correct the brain volume for these factors? Because in a direct comparison there is practically no difference in the brain size of the two types of people, the researchers discovered: The average volume of the Neanderthals was 1,473.46 cubic centimeters and that of Homo sapiens 1473.84 cubic centimeters. However, if you take out the visual center and body control, there are still 1332.41 cubic centimeters left for Homo sapiens and 1133.98 cubic centimeters for Neanderthals. In fact, the extinct early humans had less brain mass available than our ancestors, so the researchers' conclusion.

Even if this difference doesn't seem extreme, it could have made all the difference. There is a direct connection between the size of a living being's brain and its ability to live in groups. The larger the brain and especially certain parts of the frontal lobe, the better life functions in larger groups. The reason for this: In order to live successfully with others, you have to be able to empathize with them - and that takes a lot of brainpower. Therefore, the number of conspecifics whose thoughts and plans a single individual can keep an eye on, determines the largest possible group size. Today researchers estimate this maximum size at around 150 individuals, 27,000 to 75,000 years ago our ancestors had around 139. The Neanderthals, on the other hand, could only manage groups of up to 115 people.

Smaller groups, that also means a smaller overall populated area - and thus poorer trading and exchange opportunities as well as less access to additional resources in bad times, explain the researchers. This scenario is also supported by the few archaeological finds that have been discovered to date. They also suggested that our ancestors had larger and more extensive social networks than the Neanderthals. And perhaps, the researchers speculate, this was precisely the decisive factor that made Homo sapiens survive and its cousin, the Neanderthal man, extinct.

Eiluned Pearce (University of Oxford) et al .: Proceedings of the Royal Society B, doi: 10.1098 / rspb.2013.0168 © - Ilka Lehnen-Beyel
13th March 2013