More on Rapid Human Evolution and True Love:
I have suggested in the past that since the line that would become human and the line that would become chimpanzees parted ways millions of years ago, humans have evolved far more than chimps. I now read further information. (The Fickle Y Chromosome, Lizzie Buchan NATURE vol. 463 no, 7278 January 14, 2010 page 149.)
My point was that monogamy, “true love” if you will, is practiced however imperfectly by humans but not at all by out troglodyte cousins. This has allowed humans to dismantle, or be spared the cost of developing, the potent immune system of the chimp. Since I take it that the genome of the human, and just about every other animal, has been optimized, not developing one ability presents the opportunity to develop others. Monogamy has meant we could develop other things because we limited intimate contact with others of our kind and did not suffer from the infectious diseases such contact could transmit. Dan Onion (The Little Black Book of Primary Care 3rd edition, Dan Onion, Blackwell Science, Malden, 1999 page 818) lists 25 sexually transmitted diseases in humans. Chimpanzees have few, although they do say they can get AIDS. (Chimps can develop AIDS after all 18:00 22 July 2009 by Vian Azzu, NewScientist: HEALTH)
I am not alone in thinking that monogamy reduces disease, (Sexually transmitted diseases, pair bonding, fathering, and alliance formation: Disease avoidance behaviors as a proposed element in human evolution. By Mackey, Wade C.; Immerman, Ronald S. Psychology of Men & Masculinity. Vol 1(1), Jan 2000, 49-61) although perhaps a bit isolated in thinking that this has further implications for humankind.
What is now found is that the Y chromosome, the set of genes that determines masculinity, varies far more between chimpanzees and humans than do other parts of our genomes. “Right, I thought. Chimpanzees have spent their time evolving sperm that can compete with other sperm along with their thoroughbred immune system so as to compete with each other, while we developed the skills for making epic poetry and doing text messaging.” Wrong. Human Y chromosomes have half again as many genes as chimpanzee Y chromosomes and more than twice as many protein-coding elements. It seems we have invested more in our masculinity than they have.
Of course a lot of this may have to do with pair bonding after all. Seems strange. Females can pair bond, or so they tell us. So I am sticking to my guns; monogamy made us human. But I feel chastened. There is still a lot to be understood.
While I am on the subject of human evolution, another article comes to mind. (The Naked Truth, Nina G. Jablonski SCIENTIFIC AMERICAN vol. 302 no. 2 February, 2010 page 42) Personal prejudice leads me to avoid reading anything with “naked” in the title. The word screams, “This is nothing by hype.” But I toughed it out.
The article is about why humans have no hair. The short answer is that we shed it in order to avoid overheating when in on long marches in the sun. but here are problems that are not successfully resolved. Other bald mammals are far larger than us or are aquatic. But they carry hair. Dogs also travel long distances in the sun. They have hair.
The notion that we were ever aquatic is dismissed with the concepts that 1) Other aquatic animals very in the amount of hair they have … yes … and …? 2) There were dangerous animals in the water … and not on the land? 3) The theory is not necessary, so we don’t have to believe it … and the heat overload theory is without problems?
I mean look. We are supposed to have retained the hair on our heads to shield us from direct sunlight to our noggins. That makes sense. But women have a lot of hair up there and men in some lineages tend to go bald. Was it the women who were out chasing antelopes while the men nursed the babies?
Besides as I have mentioned there are complex defenses of the human upper airway against water aspiration. I could owe my life to the fact that I stop my nose with my upper lip, and this could have kept me from getting fatal amebae in the brain from blood-warm Florida water as a child. Then there is the human diving reflex: water slows our metabolism and – I have been told – a human swimming underwater to exhaustion will lose consciousness and settle to the bottom or top where rescue is possible. Surely we have been pulling each other out of the water for a long time.
And then there is the fact that Australopithecus had big feet. Why should we evolve big feet and then evolve small feet again unless the environment had changed, like we used the feet like swim fins?
There is the usual saw about skin color and sunlight. Heavy melanin in the skin prevents sunburn. But it certainly does not keep one cool. It does just the opposite.
There is another down side. Heavy pigmentation reduces the body’s ability to absorb ultraviolet light and make vitamin D. Years ago I was at a staff meeting in a rural Florida hospital, and the speaker said in a self satisfied tone, “You probably don’t realize it, but the biggest cause of rickets today is diet, not parathyroid problems as you would expect. In the third world they still get rickets because of their poor diet.” When the meeting broke up another young doctor got my attention. I looked into his brown face and sloe eyes, and he said, “Just where does he think we are all from?” There was, of course, hardly a fish belly face in the room. Just because you are from a poor part of the world does not mean children get enough sun to prevent rickets. I suspect that it is in part cosmetic; dark skin looks better at more ages and under more circumstance.
There is due note taken that textiles can substitute for fur (although tattoos but not clothing are proposed as status symbols adopted to replace the status of a fine pelt) but it was a long time between the loss of hair and the origin of clothing. But what about animal furs? Imagine a feast in which an animal has been skinned, cooked and eaten by a tribe. The hide lies discarded. Does it really take a genius to crawl under the hide when the chill of night sets in? It’s easy enough to lug it around during the day so it can be used as a sun shield as well.
Fur, like feathers, takes a lot of maintenance. Watch chimpanzees for a while. They improve the time of any break by grooming each other. Bald skin cleans off easily.
And there is the usual mention that human hair provides no warmth. On a personal note again, I was once foolish enough to walk a few miles in Boston one night without a jacket. The temperature was 4o Fahrenheit. It was dry and quite still. (Don’t try this one yourself.) I avoided frostbite by putting one hand in a pocked and the other over nose or an ear and then when the pain reached a certain point swapping hands. But core temperature was no problem for my young and highly revved metabolism. I had nothing on above the waist but a long sleeved cotton shirt. I buttoned it up and in the chill I got gooseflesh. My body hair bristled up almost half an inch. The result was a layer of trapped air lighter and warmer than any sweater I ever wore.
So I conclude that people, probably including me, simply cannot talk about skin and make much sense.
M. Linton Herbert MD
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