Big eyes caused Neanderthal’s demise, according to articles in ABC News in Science, BBC News and New Scientist 13 March 2013.

Eiluned Pearce and Robin Dunbar of Oxford University have compared 13 Neanderthal skulls with 32 Homo sapiens skulls and found the Neanderthals had larger eye sockets, by an average of 6mm as measured from top to bottom. (6mm is a little less than a quarter of an inch.) The researchers claim this indicates they had larger eyes, and therefore needed to use more of their brain to process visual information. This left less of their brain available for higher functions, such as forming social groups and developing new tools. Therefore they lost out in the struggle to survive in the ice age.

According to Chris Stringer of the natural History Museum, who was also involved in the study, “We infer that Neanderthals had a smaller cognitive (thinking) part of the brain and this would have limited them, including their ability to form larger groups. If you live in a larger group, you need a larger brain in order to process all those extra relationships”. He went on to say: “Even if you had a small percent better ability to react quickly, to rely on your neighbours to help you survive and to pass on information – all these things together gave the edge to Homo sapiens over Neanderthals, and that may have made a difference to survival”. The research team suggest Neanderthals evolved large eyes because their ancestors evolved in a gloomy northern European climate, whist the ancestors of the Homo sapiens evolved in brightly lit Africa.

According to the BBC article “Up until now, researchers’ knowledge of Neanderthals’ brains has been based on casts of skulls. This has given an indication of brain size and structure, but has not given any real indication of how the Neanderthal brain functioned differently from ours. The latest study is an imaginative approach in trying to address this issue”.

Not everyone agrees with the link between eye size and brain function because the African Tarsiers have very big eyes but their visual systems are quite small. The BBC article admits “Previous research by Ms Pearce has shown that modern humans living at higher latitudes evolved bigger vision areas in the brain to cope with lower light levels. There is no suggestion though that their higher cognitive abilities suffered as a consequence”. The ABC article comments: “The relationship between absolute brain size and higher cognitive abilities has long been controversial, the authors admit”.

ABC, BBC, New Scientist

Editorial Comment: The BBC article’s comment: “The latest study is an imaginative approach in trying to address this issue,” we can totally agree with – with the emphasis on “imaginative”.

For a start, there are no fossilised Neanderthal eyeballs and since all living eye sockets contains muscles, support and insulating tissues as well as blood vessels and nerves that fit in the space between the eyeballs and the bony socket walls, and none of these were preserved either – just empty eye sockets, they do not know accurately know how big their eyeballs actually were. Furthermore, to use eye size to estimate how much brain capacity was needed for processing visual information it is necessary to also know how much information was being sent to their brain from the eyes, so any answer about Neanderthal’s is only a guess-timate. To really know you need and be able to study a live brain while a person is actually looking at things.

Furthermore, as the BBC article comments, even if they really did have bigger eyes and vision processing areas, that is no proof they were lacking in intelligence or social complexity. The comparative study referred to by the BBC, was of modern humans who lived at higher latitudes. They were found to have larger eyes but no-one would suggest these people were lacking in intelligence, or social skills.

Therefore, without any actual tests of intelligence, it is impossible to say how smart Neanderthals were. All studies of Neanderthal remains, along with studies of their living spaces and artefacts, put them within the present human range, even their overall brain size was larger than the modern average, so even if they used more brain space for vision they would have had plenty left for thinking, personal interaction, and other fully human activities.

The study of modern humans referred to by the BBC is “Latitudinal variation in light levels drives human visual system size”, Biology Letters, doi: 10.1098/rsbl.2011.0570, 23 February 2012.

Evidence News 27 March 2013

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