General Observations on Animals; Extinct Species

A forceful and sustained change in the environment and in the habits and ways of life of animals creates a very remarkable change in the individuals exposed to it.

A bird which flies fast but is locked in a cage will lose most of its lightness and agility.

Its body becomes more dense.

• its limbs lose power and suppleness
• its faculties are no longer the same.

In the sixth chapter of this first part, I will have occasion to prove by well known facts the power of

Changes in circumstances:

• give animals new needs
• lead to new actions

Repeated new actions bring about new habits and new tendencies.

The frequent use of an organ modifies that organ.

The same is true for plants.

The result is that we see the considerable changes which we have made in those plants we have cultivated for a long time.

Thus, among living things, nature, offers us in an indisputable manner only individuals which succeed each other in sequence one after the other in reproduction and which come from each other.

But species among them have only a relative constancy and are not invariable except temporarily.

Nevertheless, to facilitate our study and our knowledge of so many different bodies, it is useful to give the name species to the entire collection of similar individuals which reproduction perpetuates in the same condition, as long as their living circumstances do not change sufficiently to vary their habits, characteristics, and shape.

Lost Species

Fossils remains buried in the soil are the remains of various animals which have existed.

Only very few of them have analogous creatures like them now alive.

Does it mean that those species are extinct?

Many places on the earth’s surface are still undiscovered.

• These places might conceal species unknown to us

If some species were truly lost, this can only be among the large animals which live in the dry parts of the earth.

• There man could destroy those species.

However, that is only a possibility.

But the animals which live underwater are protected against man.

However, fossils show so many extinct animals.

• Most belong to the shelled mollusks.
• Only their shells remain.
• These could not have been all destroyed by man.

Those extinct species might have:

• changed over time
• given way to species presently living which we find near by

Nothing is constantly in the same state on the surface of the earth.

In time, everything there undergoes various changes more or less constantly.

The variations in the circumstances of living things lead to changes in needs, habits, and ways of life.

These changes give rise to modification of their organs and the shape of their parts.

Thus, all living bodies must vary, especially in their shapes or external characteristics.

This variation will become noticeable only after a considerable time.

This is why the dry places of the earth show fossils of so many animals which do not exist today.

It would be astonishing if we discover species that match the fossils of extinct species.

I assume that the fossil remains of animals with living analogues are the least ancient fossils.

• This has not given them time to vary in some of its forms.

No To Extinction Event

Naturalists have assumed that a universal catastrophe destroyed many species then existing.

• It is a convenient method of dealing with the operations of nature when the causes are unknown.
• It cannot be supported with a single proof.

Local catastrophes, like those which produce earthquakes, volcanoes, and other particular causes are well known.

But why should anyone assume, without proof, a universal catastrophe when the better known progress of nature can explain the facts?

Nature works slowly and by successive degrees.

The particular or local causes of disorders, revolutions, displacements, and so on, can provide reasons for everything which we observe on the surface of the earth.

These are nonetheless subject to nature’s laws.

But it is unnecessary to assume that a universal catastrophe came to destroy a large part of the very operations of nature.