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Are You Getting Goose Bumps this Winter?
by Jack Kittredge
An item I read in Science magazine recently stimulated my idle curiosity. The article mentioned the production of lactase, the enzyme mammals produce as babies to enable them to digest lactose, the sugary nutrient in milk. Without it milk, when consumed, produces bloating, gases and discomfort in the gut. Many humans lose this ability as they age past weaning, but some continue to produce it. In parts of northern Europe the trait persists among as many as 90% of the population, whereas in Southern Europe it declines to as little as 15%. Lactase production is rare in east Asia but spotty again in India and Africa, reaching both 65% and only 20% in differing parts of Sudan. After reading this I wondered if there are other abilities which we humans have lost. And if they were valuable, why did we lose them?
It turns out that there are plenty. Probably the best example is vitamin C, an essential nutrient which most animals produce. Humans, however, lost that ability back at the end of the dinosaur age when we were small primates in Africa. Apparently our diets were largely fruits full of vitamin C, whereas it’s production required first producing an enzyme called GULO, which took metabolic energy. In addition, some parasites were apparently prevented from infecting GULO deficient hosts. So losing the vitamin production cost us nothing back then (although now we seek it out to prevent scurvy and other conditions) and brought us a useful advantage.
Other examples abound. Take long hair. Most primates have that. But we lost it, presumably from our need to regulate temperature while running around on the hot savanna. We developed sweating instead, which works pretty well. But we haven’t lost goose bumps yet. When cold those tiny muscles still keep trying to fluff out our long hairs to retain body heat.
Another is ear motion. Evolved to enable use of auricular muscles around the ear for sound location, some children still have this trait and entertain their cohorts endlessly by wiggling them. It apparently has not caught on as a mating lure, however, as the trait is slowly disappearing.
Ever watch an animal approach something new? Compared to most creatures we have little use for our sense of smell. Meant as a way to identify and separate dangerous from safe and attractive things, we still have an inordinate amount of nerve tissue devoted to smell. But we are losing olfactory receptor genes as other senses (sound, sight) become more crucial to survival.
Coming down from the trees as Africa dried up ended both our arboreal years and our need for tails. Primarily used for both grasping and balance (for a thing of beauty just watch a monkey or squirrel in their aerial world), they were shortened and then eliminated when we acquired a gene called TBXT (or perhaps an intron called AluY, according to a dispute among researchers). I guess they got in our way.
Many of us have trouble with wisdom teeth. Modern diets require less chewing and have favored smaller and narrower jaws, leading to more children born without room for their third molars. They either do not come in at all, or have trouble fitting, causing pain and needing attention.
That last example brings these changes into modern times, showing evolution has not stopped. Shortly before World War II dentist Weston A. Price went around the world taking pictures of the jaws and facial bone structures of children in native cultures. Then he went back after the war (and the adoption of western diets everywhere) and did it again. The degeneration of the children’s jaws, in just one generation by dietary change, was remarkable and can be seen in his book “Nutrition and Physical Degeneration”. It seems that what we do still has consequences, and shapes us into the future.
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