Natural Selection

The principle of selection is so potent in the hands of man.

Does it apply in nature? How will the struggle for existence act in regard to variation?

Our domestic productions have a lot more variety than wild organisms.

How Strong is the Hereditary Tendency?

Under domestication, the whole organisation becomes plastic.

The mutual relations of all organic beings to each other and to their living conditions are infinitely complex and close-fitting.

In the course of thousands of generations, useful variations also occur in the wild.

The individuals which have any advantage over others, however slight, would have the best chance of surviving and of procreating.

Any injurious variation would be rigidly destroyed.

Natural Selection is this:

• preservation of favourable variations
• rejection of injurious variations

Variations neither useful nor injurious would not be affected by natural selection.

They would be left a fluctuating element, as we see in the “polymorphic” species.

We best understand the probable course of natural selection by looking into physical changes in the country, such as climate change.

The proportional numbers of its inhabitants would almost immediately undergo a change. Some might become extinct.

Any change in population, independent of climage change itself, would most seriously affect many of the others.

If the country were open on its borders, new forms would immigrate.

This also would seriously disturb the relations of some of the natives.

This is proven by the influence of a single introduced tree or mammal.

If an area is open to immigration, these same places would be seized on by intruders.

The course of time would lead to slight modifications.

Natural selection would thus have free scope for the work of improvement.

A change in the conditions of life, by specially acting on the reproductive system, causes or increases variability.

It gives a better chance of profitable variations occurring.

Unless profitable variations do occur, natural selection can do nothing.

An extreme amount of variability is not necessary.

Man can produce great results by adding up individual differences. Nature could do this far more easily as she has longer time at her disposal.

Any great physical change, such as of climate or unusual isolation, is not necessary for natural selection.

This is because all are struggling together with nicely balanced forces. Extremely slight modifications in the structure or habits of one inhabitant would often give it an advantage over others.

Nature can act on every internal organ, on every shade of constitutional difference, on the whole machinery of life.

Man selects only for his own good;

Nature only for that of the being which she tends. Every selected character is fully exercised by her; and the being is placed under well-suited conditions of life.

Man keeps the natives of many climates in the same country.

In the wild, the slightest difference of structure or constitution may turn the balanced scale in the struggle for life.

This is why nature’s productions are far ’truer’ in character than man’s productions.

They are infinitely better adapted to the most complex conditions of life.