Evolution Social and Organic

by Arthur M. Lewis

This is what happens. First the leaves are eaten from all the lower branches as they are reached with the least effort. Then they go higher and still higher until the point is reached where number one with the shortest neck cannot reach any further and the terrible struggle for existence begins. Number two sees no danger as yet and number three has things all his own way. But with short-necked number one, a tragedy has begun. Every day now sees the food further out of his reach and even number two is obliged to reach out for his supply. The breeding time is approaching but the longer necked and therefore well-fed and vigourous females will have nothing to do with this wobbley starving creature, and the longer necked, well-fed males shun the short-necked starving females. If the starving ones mate, the mother dies before giving birth to offspring, or she cannot get nourishment enough to rear her progeny; in either case there is no effective succession. So the longer-necked are the fittest and they survive. Thus does nature “select” one by the negative process of destroying the rest, in about the same way as a man “selects” one puppy in a litter by drowning the rest.

In the case of the puppies we may say “artificial selection;” in the case of the giraffe it is “natural selection.” And this theory, simple as it may seem here, revolutionized Biology.

It is worthy of note that “natural” selection has many advantages over “artificial” selection. The breeder may be mistaken; he may select the wrong puppy and drown its superior. The horse that won the great race may have had a fleeter-footed companion in the same stable had the trainer known how to develop his possibilities. The gardener may have passed the best root or stem through carelessness. But nature makes no such mistakes, or if she does she eventually redeems them. Her method, while it is wholly fortuitous and unintelligent, is practically infallible. The condition of survival is, adaptation to environment. The very process of selection is, in itself, a sure test of fitness. True, moral considerations are eliminated—at least in the non-social world—yet nature offers something like a fair field and no favors. When we speak of nature’s favorites, we simply mean those who are best fitted to meet her hard conditions.

Take a row of celery plants, from which future seedlings are to be “selected.”

In this instance, let us suppose, the quality desired is ability to resist frost. How is the gardener to know which of fifty plants are the “best” in this respect. He has no method of finding out with any degree of certainty. But nature comes along some night with a sharp frost and “selects” ten by killing forty. And the very act of this “natural” selection proves that these ten are better able to withstand the frost than their fellows.

Breeders of white sheep who supply the white wool market have a very tangible guide—they kill every lamb that shows the least tinge of black. But even here, nature is not to be out-done. In Virginia there is—or at least was in Darwin’s day—a wild hog of pure black. One of its staple foods was known as the “paint-root.” Any hog with the least speck of white on its body was poisoned by this root while its all-black brothers found it a health-sustaining and succulent food.

In an environment which remained constant and where a species of animals had reached a population which strained the limits of subsistence—food supply—those offspring which most closely resemble their parents, who had won out in that environment, would again succeed and be selected. While if the environment changed—became warmer or colder for example—those descendants which happened to vary in a direction making them better able to cope with the new conditions would be selected for survival as against those who resembled their parents, which parents had survived in their day because they were adapted to the prior environment.

For example, a country is well supplied with water and it is as a consequence fertile and “green.” In such a country green insects and green reptiles will be selected, because a green background will render them almost invisible to their enemies. Individuals of other colors will make their appearance by variation, but they will be such plain targets to their enemies, they will be devoured before they reach breeding age and have a chance to reproduce the variation.

But suppose desiccation (drying up) sets in. The country loses its water supply, as Krapotkin has shown to have been the case in North-West Mongolia and East Turkestan, leading to the enforced exodus of the barbarians. Now green will disappear and brown or yellow—say brown—takes its place. While this change will not, so far as we know, cause insects and lizards to breed brown instead of green, it will ensure the survival or “selection” of such as are born brown and the destruction of those who breed true to their green ancestors. Now every atavistic return to green will be mercilessly weeded out, just as, when the country was well-watered and green, every sporadic production of brown was done to death.

This is the biological foundation of that environment philosophy which now pervades all our thinking. Change the physical environment, says the biologist, and the species will be transformed. Change the economic environment, says the Socialist, and, if you make the right change, the race will be redeemed. Both statements rest on the same fundamental laws.