What is Darwin’s point in chapter 10?
Chapter 10 is a general discussion of the appearance and disappearance of species in the fossil record.
He states that species once lost do not reappear.
“When a species has once disappeared from the face of the earth, we have reason to believe that the same identical form never reappears.”
Things also change at different rates.
“I believe in no fixed law of development, causing all the inhabitants of a country to change abruptly, or simultaneously, or to an equal degree. The process of modification must be extremely slow. The variability of each species is quite independent of that of all others.”
On extinction, he says that disappearance is slower than appearance.
“There is reason to believe that the complete extinction of the species of a group is generally a slower process than their production”
As for specifically why species becomes extinct, he can offer no definitive answer.
“If we ask ourselves why this or that species is rare, we answer that something is unfavourable in its conditions of life; but what that something is, we can hardly ever tell.”
One interesting observation he notes is that life seems to change simultaneously across the globe.
“Scarcely any palaeontological discovery is more striking than the fact, that the forms of life change almost simultaneously throughout the world.”
The only answer he has to this is that dominant species must’ve overwhelmed other species. But, he acknowledges that “we know not at all precisely what are all the conditions most favourable for the multiplication of new and dominant species;”
But for all these points in the chapter, I do not really see how they offer any support to his theory of natural selection.