Mechanism of Evolution

Mechanism of Evolution

That the mechanism of evolution is natural selection is the great discovery associated with the names of Charles Darwin and Alfred Russel Wallace. More than a century ago, these two scientists stressed that nature is prolific, that many more animals and plants are born than can possibly survive and that therefore the environment selects those varieties which are, by accident, better suited for survival.

Mutations – sudden changes in heredity – breed true. They provide the raw material of evolution. The environment selects those few mutations that enhance survival, resulting in a series of slow transformations of one lifeform into another, the origin of new species.

Evolution is a fact, not a theory, and genetic changes induced by domestication occur very rapidly. Image : © Megan Jorgensen (Elena)

The genetic changes induced by domestication have occurred very rapidly. The rabbit was not domesticated until early medieval times – it was bred by French monks in the belief that newborn bunnies were fish and therefore exempt from the prohibitions against eating meat on certain days in the Church calendar; coffee in the fifteenth century; the sugar beet in the nineteenth century; and the mink is still it the earliest stages of domestication. In less than ten thousand years, domestication has increased the weight of wool grown by sheep from less than one kilogram or rough hairs to ten or twenty kilograms of uniform, fine down; or the volume of milk given by cattle during a lactation period from a few hundred to million cubic centimeters. If artificial selection can make such major changes in so short a period of time, what must natural selection, working over billions of years, be capable of? The answer is all the beauty and diversity of the biological world.

Darwin’s words in the Origin of Species were: Man does not actually produce variability; he only unintentionally exposes organic beings to new conditions of life, and then Nature acts on the organisation, and causes variability. But man can and does select the variations given to him by Nature, and thus accumulate them in any desired manner. He thus adapts animals and plants for his own benefit or pleasure. He may do this methodically, or he may do it unconsciously by preserving the individuals most useful to him at the time, without any thought of altering the breed… There is no obvious reason why the principles which have acted so efficiently under domestication should not have acted under Nature… More individuals are born than can possibly survive… The slightest advantage in one being, or any age or during any season, over those with which it comes into competition, or better adaptation in however slight a degree to the surrounding physical conditions, will turn the balance.