Natural Selection n. the process in nature by which forms of life having traits that better enable them to adapt to specific environmental pressures, as changes in climate or competition for food or mates, will tend to survive and reproduce in greater numbers than others of their kind, thus perpetuating those traits in succeeding generations (c 1885)
Genetic Drift. random changes in the frequency of alleles in the genetic pool, usually of small populations. (c 1955)]
Does everyone understand that the idea of evolution (without regard to your individual beliefs) doesn't have anything to do with planning on the part of the species involved? Apparently not. I just finished reading a book (Omnivore's Dilemma) whose author speaks of mushrooms, "learning to hide from our view." In another book, whose authors should know better, (The Beak of the Finch) about birds on the Galapagos Islands, proof of evolution is claimed when birds hatch young with stronger beaks whenever a bumper crop of hard seeded plants is "anticipated."
Darwin wrote nothing to support either of these anticipating results. As far as anyone knows, plants and fungi and most animals don't plan or anticipate anything, they respond to environmental cues such as day length, temperature changes, precipitation, etc. but they certainly don't plan to learn how to hide from people or produce young with stronger beaks.
The simple fact that Morels have a shape and color and texture that make them harder to see than if they were bright yellow and shaped like tea cups may be the result of evolution, or it might not. Evolution is generally thought of as a positive thing. A species evolves to better function in its environment. In Morels, the shape/color/texture attributes (if indeed the original Morel was different) may better indicate a devolution. Not literally, as in disappearing from our view; ie. hard to see, but, in this instance actually being detrimental to the survival of the species. The fruiting bodies of mycelium, mushrooms, are the means of spreading the fungus beyond its present site, which may be an acre or more, almost all underground. If no eater of Morels can see it and if the wind doesn't blow, the spores may not disburse far. So, by "learning to hide" the Morel has done itself a disservice.
In the case of the Galapagos finches, the variation in beak size and strength is probably always present with every nesting. When the plants that produce harder seeds have a particularly good year, to the detriment of other, softer seeded plants, the stronger beaked birds find more nourishment and are able to breed better. Some will breed with wimpy beaked mates and some will breed with stronger beaked mates. The result, over time, may be an evolved (fixed) trait of a stronger beaked finch. As long as hard seeds dominate the available feed, these birds will have a competitive advantage. But these bird's parents certainly didn't set out to produce stronger beaked young in anticipation of hard seeds.
The traits that result in the evolution of a species are generally thought to be genetic accidents or, possibly in the finch beak, the result of some natural variation within a species being given a competitive advantage by an environmental change.
For over a hundred years, archaeologists thought the Woolly Mammoth disappeared from North America because it couldn't cope with climate change. From an evolutionary perspective the Mammoth population didn't contain enough natural variation to have some individuals who could survive the changes. That always sounded wrong to many thinkers because the Woolly Mammoth was highly mobile and could have moved. The theory covered that problem by deciding that the Mammoth's habitat was first surrounded by this hostile environment before it closed in, leaving the Mammoth no place to go. Recently, new thinkers think that climate change had nothing to do with the Mammoth's demise. There was, however, apparently a surrounding hostile environment in the form of humans. The Clovis People, it is now thought, hunted the Woolly Mammoth to extinction. Supporting evidence includes the disappearance of the Clovis People shortly after the Woolly Mammoth disappears from the record.
What does the Woolly Mammoth have to do with evolution? Probably nothing by itself but it may be the ultimate cause of the extinction of the Clovis People, who apparently also had insufficient natural variation to adapt to a different food source. If that's the case, the Clovis People are an anomaly among humans. Humans are possibly the most adaptable species on earth. Of course, we now know how to cheat by carrying our environment along with us anywhere we decide to go. But the Eskimo peoples thrived north of the Arctic Circle, especially before Europeans discovered that Eskimos had no whiskey. Humans can thrive in polluted air, on polluted water, in unsanitary conditions, while eating unhealthy food.
So does it really make sense that the Clovis People ate every last Woolly Mammoth and then just sat at the mouth of their caves and starved to death? Well, you say, of course not. Their wives sent them out every day to hunt. As everyone got hungrier and hungrier the wives began to wonder if the men were just going out far enough to be out of sight and were really playing cribbage all day.
Meanwhile, there is historical evidence of native peoples eating bugs to get through the hard times until they could hunt or the dogs got a little fatter. So what's with these elitist Clovis People?
I don't know. But if the Woolly Mammoth/Clovis People link is true it is one of the earliest instances of a specialized diet, like Koala Bears and eucalyptus leaves.
If you could take an active part in planning and executing your own species' evolution, wouldn't the Woolly Mammoth and the Clovis People still be around? Woolly Mammoths would have developed a disgusting taste and odor so no one, not just Clovis People, would want to eat them, and the Clovis People would have banned cribbage boards. But who was to know?
I agree with your two complaints they were either sloppy writing not caught by editors with weak scientific standards. It is possible to write to a lay audience without slipping into a kind of lazy anthropomorphic language.
ReplyDeleteOnly one quibble. The morels may be hard to see to us and therefore we are lousy spore dispersers but we are only one of many possible mammalian dispersers and the others may have vision that better sees morels or a sense of smell that finds them with some ease. Of all possible dispersers we walk taller and have lousy senses of smell compared to other possible dispersers.
If climte doomed the Clovis People it had to have wiped out a broad range of possible foods and I assume with some rapidity or the would have moved though we always see pictures of people being rescued from (fill in the blank) who stayed to tough it out but they are a minority.