The Life and Letters of Charles Darwin – Day 124 of 188

At another place, speaking of intermediate forms he says:–

“Cuvier objects to propagation of species by saying, why have not some intermediate forms been discovered between Palaeotherium, Megalonyx, Mastodon, and the species now living? Now according to my view (in S. America) parent of all Armadilloes might be brother to Megatherium–uncle now dead.”

Speaking elsewhere of intermediate forms, he remarks:–

“Opponents will say–‘show them me.’ I will answer yes, if you will show me every step between bulldog and greyhound.”

Here we see that the case of domestic animals was already present in his mind as bearing on the production of natural species. The disappearance of intermediate forms naturally leads up to the subject of extinction, with which the next extract begins.

“It is a wonderful fact, horse, elephant, and mastodon, dying out about same time in such different quarters.

“Will Mr. Lyell say that some [same?] circumstance killed it over a tract from Spain to South America?–(Never).

“They die, without they change, like golden pippins; it is a generation of species like generation of individuals.

“Why does individual die? To perpetuate certain peculiarities (therefore adaptation), and obliterate accidental varieties, and to accommodate itself to change (for, of course, change, even in varieties, is accommodation). Now this argument applies to species.

“If individual cannot propagate he has no issue–so with species.

“If species generate other species, their race is not utterly cut off:– like golden pippins, if produced by seed, go on–otherwise all die.

“The fossil horse generated, in South Africa, zebra–and continued– perished in America.

“All animals of same species are bound together just like buds of plants, which die at one time, though produced either sooner or later. Prove animals like plants–trace gradation between associated and non-associated animals–and the story will be complete.”

Here we have the view already alluded to of a term of life impressed on a species.

But in the following note we get extinction connected with unfavourable variation, and thus a hint is given of natural selection:

“With respect to extinction, we can easily see that [a] variety of [the] ostrich (Petise), may not be well adapted, and thus perish out; or, on the other hand, like Orpheus [a Galapagos bird], being favourable, many might be produced. This requires [the] principle that the permanent variations produced by confined breeding and changing circumstances are continued and produced according to the adaptation of such circumstance, and therefore that death of species is a consequence (contrary to what would appear from America) of non-adaptation of circumstances.”

The first part of the next extract has a similar bearing. The end of the passage is of much interest, as showing that he had at this early date visions of the far-reaching character of the theory of evolution:–

“With belief of transmutation and geographical grouping, we are lead to endeavour to discover causes of change; the manner of adaptation (wish of parents??), instinct and structure becomes full of speculation and lines of observation. View of generation being condensation (I imagine him to mean that each generation is “condensed” to a small number of the best organized individuals.) test of highest organisation intelligible…My theory would give zest to recent and fossil comparative anatomy; it would lead to the study of instincts, heredity, and mind-heredity, whole [of] metaphysics.

“It would lead to closest examination of hybridity and generation, causes of change in order to know what we have come from and to what we tend–to what circumstances favour crossing and what prevents it–this, and direct examination of direct passages of structure in species, might lead to laws of change, which would then be [the] main object of study, to guide our speculations.”

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