The university of life

The naked ape - or why don't we have a thick coat of fur?

During a recent lecture a student raised his hand. At first I thought that he had to be excused to visit the toilet for some bodily relief after I saturated his mind with pure knowledge. Instead he asked me a question; 'Prof. Spuriousmonkey (I insist on etiquette), why don't we have a thick coat of fur such as other mammals'? I felt mature enough not to ridicule his bravery in front of the classroom by immediately replying that contrary to popular belief there do exist other mammalian species which do not indulge in the luxury of a beautiful fur. We only have to think about the rather rich group of cetaceans roaming the seas and the plates of Japanese cuisine lovers.

Obviously the student meant to ask why humans do not have a similar amount of fur compared to other primates. The answer is not that we were once an aquatic ape and we lost our fur as an adaptation to aquatic life, although our ancestors might have had a brief fling with the watery element. We lost our fur simply because we have huge heads. Huge heads contain huge brains (with notable exceptions) and the brain is the most energy consuming organ in the body relative to its size. It burns copious amounts of pizza or other food particles.

A Japanese group covered 2 groups of volunteers (students) with artificial fur in the early 1970s. The then measured the heat dissipation of both groups. One group just had the artificial fur; the other group had their heads in a portable vice. The decreased the average size of the heads of this latter group with the vice on average by some 10%. This reduced head group had a lower core temperature than the control group who were overheating.

But was it the size of the brain that mattered? American scientists led by a Nobel Prize laureate discovered this gem of a study in the late 1990s and went a step further. Once again they had two groups of volunteers (students) covered with artificial fur. In one group they surgically reduced the size of the brain by 20%. With the other group they merely opened the skull, but left the brain alone. Once again the reduced brain group produced less heat and maintained a lower core temperature. Clearly both these studies seem to support the notion that the immense heat production of our big brain required the evolution of a furless, or in technical terms, a naked skin.

Interestingly the reduction of the brain size in students did not reduce the performance of the students in any test afterwards.


Professor at the UOL

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