Human Caused Evolution

Today’s installment concludes Luther Burbank’s Accomplishments,
the name of our combined selection from Garrett P. Servtss and David Starr Jordan. The concluding installment, by David Starr Jordan from an article in Popular Science Magazine.

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Previously in Luther Burbank’s Accomplishments.

Place: Santa Rosa, California

It is questioned whether competition in minor details or “intraspecific selection” can form species permanent as wild species are. As to this, Mr. Burbank notes that the cultivated species produced by selection “have a very brief history compared with the wild species, and, moreover, they are constantly being placed in a new environment by man, being influenced by new soils, new climates, new fertilizers, and the like.” “Breeding to a fixed line will bring fixed results. Man’s desultory breeding is brief, the struggle for existence is mostly absent, and new ideals and new uses are required instead of ability to endure under natural conditions. Man’s efforts at selective breeding are fluctuating with frequent saltations.” ‘

Crossing is done to secure a wealth of variation. By this means we get the species into a state of perturbation or ‘wabble,’ and take advantage of the ‘wabbling’ to guide the life forces into the desired habits or channels. The first crossing is generally a step in the direction in which we are going, but repeated crossing is often necessary and judicious selection always necessary to secure valuable practical results. Crossing may give the best or the worst qualities of the parent, or any other qualities; and previous crossings often affect the results. ”

Hybridization differs from ordinary crossing only in degree. A species is only a race which has assumed greater fixity. The purposes and results of crossing within the species and of hybridization of different species are essentially alike. The formation of the new individual by the sexual relation of two parents is in itself a species of crossing, giving each new individual in its degree new traits or new combinations.”

Bees and other insects, as well as the wind, cross plants, but they do not work intelligently, therefore rarely to any advantage economically to man. No mechanic could invent such devices as those which tend to prevent self-crossing in plants. All evolution and improvement are dependent on crossing, therefore nature has produced more wonderful devices for this purpose than for any other.”

Mutations, or saltations, are often found; that is, fixed forms springing up, generally from unknown causes, forms which are not hybrids, and which remain constant; as, for instance, colored flowers which yield white forms, these yielding white constantly in their progeny. These mutations can be produced at will by any of the various means which disturb the habits of the plant. It comes out when the conditions are ripe. New conditions bring out latent traits. I should expect mutations to arise in the American primrose and most other plants under wholly new conditions. Extra food or growth force as well as crossing favors variation, as does abrupt change of conditions of any kind. Five or six generations will usually fix a mutation. Sometimes it is fixed at once.”

The evolution of a species is largely dependent on crossing the variations contained within it. Forms too closely bred soon run out, because generally only by crossing does variation appear. It is of great advantage to have the parents a certain distance apart in their hereditary tendencies. If too close together there is not range enough of variety. If too far apart, the developed forms are unfitted for existence be cause too unstable. Correlated changes work together to produce the effect of mutations. Environment effects a permanent change in species by selection of those which fit it or by producing changes in individuals which are better equipped to survive. Heredity is the sum of all past environment, conditions both latent and apparent. Latent traits often arise when circumstances make them possible. Environment of a life time does not necessarily or usually appear in another life time, but continues in the same direction, and will strike into the nature of the plant in time. We may refer to Emerson’s remark on the baking into the picture of the pigment laid down by environment. Selection is ‘cumulative environment.’ Fortuitous variations occur everywhere. They come up all the time, from past environments, past heredity, and present opportunity. No two individuals are alike. Where there is a marked tendency in one direction, we have the case of a persistent effect of environment. Monstrosities are engorgements of force. They are generally a thousand times more likely to develop another sort of monstrosity than normal individuals are. You are likely to get from sports and monstrosities either extreme of variance. They do not, however, maintain themselves, because heredity pulls back their descendants. A wide variance is more easily pulled back than a slight variance. There are cases where the monstrosity might pull back its species. This is more likely to happen if the forces of natural or artificial selection were in its favor. There are many cases where the variant in minor points is prepotent and outweighs the original stock. Monstrosities produced by crossing often perpetuate themselves as well as the species does. ”

The mutation theory of the origin of species seems like a step backward toward the special creation theory, and without any facts as yet adequate to support it as a universal theory, however valuable and suggestive the experiments along this line may be.”

A character may be latent through many generations or centuries, appearing when the right cross brings it out; or it may appear under specially favorable or peculiar conditions of growth.”

According to Burbank, “the facts of plant life demand a kinetic theory of evolution, a slight change from Huxley’s statement that ‘ matter is a magazine of force ‘ to that of matter being force alone. The time will come when the theory of ions will be thrown aside and no line left between force and matter. We can not get the right perspective in science unless we go beyond our senses. A dead material universe moved by outside forces is in itself highly improbable, but a universe of force alone is probable, but requires great effort to make it conceivable, because we must conceive it in the terms of our sense experience.”

This ends our selections on Luther Burbank’s Accomplishments by two of the most important authorities of this topic:

• an article in Cosmopolitan Magazine by Garrett P. Servtss.
• an article in Popular Science Magazine by David Starr Jordan.

Garrett P. Servtss began here. David Starr Jordan began here.

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