Shadows of Forgotten Ancestors

Consider the diverse specializations that, through artificial selection, we’ve generated in dogs—greyhounds and borzois for speed, to outrun the wolves; collies for herding sheep; beagles, pointers, and setters for hunting; Labrador retrievers for helping fishermen gather their nets; guide dogs for the blind; bloodhounds for tracking criminals; terriers for worrying prey out of burrows; mastiffs for guard duty; and the original Pekinese (of which only a dwarf remnant remains) for war. We did all that, in only a few thousand years, by meddling with the sex lives of dogs. We evolved cauliflower, rutabaga, broccoli, brussels sprouts, and the now common and luxuriant cabbage from the sorry wild cabbage (these vegetables, like the different breeds of dogs, remain interfertile). Now think of a much more rigorous, much more stringent selection operating on all of Nature over an expanse of time a million times longer—and established not by the conscious meddling of dog or plant breeders with some idea of what kind of dog or plant they’re aiming for, but by a blind, purposeless, and changing environment. If artificial selection represents an experiment of gigantic proportions, what must be the dimensions of the experiment that natural selection has performed? Isn’t it plausible that all the elegantly adaptive diversity of life on Earth could thereby be sifted and extracted? Indeed, it is the only known process that adapts organisms to their environments.³

Here are the passages from Darwin’s Origin of Species in which he first develops the point and counterpoint of artificial and natural selection:One of the most remarkable features in our domesticated races is that we see in them adaptation, not indeed to the animal’s or plant’s own good, but to man’s use or fancy. Some variations useful to him have probably arisen suddenly, or by one step … But when we compare the dray-horse and race-horse, the dromedary and camel, the various breeds of sheep fitted either for cultivated land or mountain pasture, with the wool of one breed good for one purpose, and that of another breed for another purpose; when we compare the many breeds of dogs, each good for man in different ways; when we compare the game-cock, so pertinacious in battle, with other breeds so little quarrelsome, with “everlasting layers” [of eggs, which never desire to sit, and with the bantam so small and elegant; when we compare the host of agricultural, culinary, orchard, and flower-garden races of plants, most useful to man at different seasons and for different purposes, or so beautiful in his eyes, we must, I think, look further than to mere variability. We cannot suppose that all the breeds were suddenly produced as perfect and as useful as we now see them; indeed, in many cases, we know that this has not been their history. The key is man’s power of accumulative selection: nature gives successive variations; man adds them up in certain directions useful to him. In this sense he may be said to have made for himself useful breeds.

… [H]ardly any one is so careless as to breed from his worst animals …

If there exist savages so barbarous as never to think of the inherited character of the offspring of their domestic animals, yet any one animal particularly useful to them, for any special purpose, would be carefully preserved during famines and other accidents, to which savages are so liable, and such choice animals would thus generally leave more offspring than the inferior ones; so that in this case there would be a kind of unconscious selection going on …

Man … can never act by selection, excepting on variations which are first given to him in some slight degree by nature …

This preservation [in Nature] of favourable individual differences and variations, and the destruction of those which are injurious, I have called Natural Selection, or the Survival of the Fittest Variations neither useful nor injurious would not be affected by natural selection …

When we see leaf-eating insects green, and bark-feeders mottled-grey; the alpine ptarmigan white in winter, the red-grouse the colour of heather, we must believe that these tints are of service to these birds and insects in preserving them from danger …

If it profit a plant to have its seeds more and more widely disseminated by the wind, I can see no greater difficulty in this being effected through natural selection, than in the cotton-planter increasing and improving by selection the down in the pods on his cotton-trees …