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Darwin Correspondence Project

To Charles Lyell   30 July 1837

36 Gt. Marlboro’ Stt.

July 30th. 1837.—

I believe there are 27 land birds from the Galapagos, all new except one, (a species of very wide range) yet all of an American form, some north, some south, Now as the Galapos is on the Equator is not this curious— Reptiles the same— Has your late work at shells startled you about the existence of species?1 I have been attending a very little to species of birds, & the passages of forms, do appear frightful—every thing is arbitrary;2 no two naturalists agree on any fundamental idea that I can see. I had a most interesting morning with Owen (who is gone to rest for a month in the N. of England) at the Coll. of Surgeons—3 We made out the rems. of 11 or 12 great animals, besides these some rodents, one of wh. is a distinct species, but most strictly S. American genus. At Bahia Blanca there were no less than five great Edentatas! what could these monsters have fed upon— I am well convinced like the present Armadillos they lived on land nearly desert— I have worked out the non relation of bulk of animals & luxuriance of vegetation, & I have been perfectly astonished at some of the facts given me by Dr. Smith.4 If it would be any satisfaction to you I think it could be proved rhinoceroses live upon air, certain it is they must be light feeders. What will you say to the tusk of a boar like the African species being imbedded with the Edentata. Lastly I am sure when you read my evidence (& see the tooth) you will be as much convinced as I am that a horse was formerly common on the Pampas as at the present day.5 What an extraordiny. mystery it is, the cause of the death of these numerous animals, so recently, & with so little physical change.—6


Lyell’s classification of the Tertiary strata depended upon the proportion of living and extinct species in each formation (Wilson 1972, pp. 443–4; Rudwick 1978). CD was at this time much concerned with the longevity of species, see n. 6 below.
In July 1837 CD opened his first notebook on ‘Transmutation of Species’ (Notebook B).
Richard Owen who described CD’s Beagle specimens for Fossil Mammalia.
Andrew Smith had informed CD that South Africa supported many large mammals in spite of its relatively dry climate (Journal and remarks, pp. 99–101).
CD had doubted that a horse’s tooth he had found in the Pampas tosca formations could be contemporaneous with other fossil bones found there, but later in the voyage, on reading in Beechey 1831, Appendix, p. 348, that horses’ bones had been found with fossil elephants, he became convinced that ‘a horse coexisted with the Megatherium & Mastodon’ (DAR 33: 253 v.; see also Journal and remarks, pp. 149–50).
Entries in the Red notebook made earlier in 1837 show CD’s interest in the length of time that each species existed, and the causes of their extinction: ‘Tempted to believe animals created for a definite time:—not extinguished by change of circumstances:’ (p. 129); ‘There is no more wonder in extinction of species than of individual.—’ (p. 133).


Galapagos land birds and reptiles.

No two naturalists agree on any fundamental idea [of species]. "Everything is arbitrary."

Has been with Richard Owen going over the S. American fossils.

Has worked out the non-relation between animals’ bulk and luxuriance of vegetation.

The horse once common on the Pampas. The mystery of the extinction of these animals.

Letter details

Letter no.
Charles Robert Darwin
Charles Lyell (1st baronet)
Sent from
London, Gt Marlborough St, 36
Source of text
Lady Lyell, Kinnordy, Kirriemuir
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 367,” accessed on 29 June 2017,

Also published in The Correspondence of Charles Darwin, vol. 2