Lane himself weighs in!

After discussing my human hairlessness idea with my professor last night, I sent the following email to Dr Lane last night asking what he thought about it and whether or not it made sense:

Dr Lane,

I am an undergrad at Utah Valley University studying bioinformatics and a big fan of your books! Last year, one of my professors turned me on to Life Ascending I couldn't put it down. I am trying to nail down a topic for an undergraduate thesis and I have an idea from Power, Sex, Suicide and was was curious whether or not you or anyone else has ever thought about this and if it makes sense in the first place.

I have been looking into the issue of human hairlessness. In this months issue of Scientific American Jablanski argues that a combination of hairlessness and specialized sweat glands evolved to prevent overheating while chasing down prey on open savanna.

At the end of Power, Sex, Suicide, you talk about the fact that humans already live several times longer than we should for our size and suggest that perhaps similar to birds, but not to the same extent, we may have already increased our lifespan by increasing our mitochondrial capacity and increasing our sensitivity to free radical signalling.

You suggest that this selection possibly occurred because extended lifespan enabled elders to pass on important information to their descendants.

If this is true, then wouldn't it follow that humans are generating more heat? I know there are debates in the literature about whether or not the heat of the open savanna would be enough to explain the evolution of hairlessness in humans. What I am wondering, is if your idea that humans may have increased mitochondrial capacity may have tipped the scales in favor of hairlessness because of the combination of extra heat generated by increased mitochondrial capacity and the heat of the open savanna.
So, I am wondering if linking these 2 things makes any sense at all. As you mention in your book birds do have a slightly higher body temperature because of their higher capacity. Does it make sense to assume that humans generate slightly more heat than other mammals of similar size and as such would have more of a reason to go hairless?


Dr Lane's response:

That's a very interesting idea. The short answer is it certainly makes sense as an idea, but I've never heard of any data that would support it. But all that means is that I think the body temperature of a gorilla is around 37C, as is our own. And as you say, we would lose more heat than a gorilla simply because we are hairless, and so it follows that they would be the same.

Excellent idea! How to test it? I suppose you'd need accurate information on mitochondrial density in different tissues; ideally the level of uncoupling (possibly similar if the difference in heat production comes down to mito density, where all mitos are leaking at the same rate); rate of heat transfer across the skin with or without hair at say 40 degrees; and body temperature (again, I assume it would be similar but the rate of heat production and heat transfer would be different). I suppose other factors might be prevailing wind, height, etc - climatic factors that might alter heat transfer, and which you might take into consideration in terms of the geography of where and when modern hairless humans evolved. Also, any info on lifespan would be useful is australopithecines vs homo sapiens, etc.

I doubt that you could track down much of this information in the time available for your project, but you can probably discuss it all in an open-ended way, and take a stab at realistic values where possible.

Good luck! Best wishes
Nick