From W. B. Cooper   4 November 1879

Dear Sir

In your “Descent of Man” after some interesting remarks on the external differences of the races of man; you conclude by ascribing them to sexual selection.¹

I thought I would venture to suggest the possibility that the color of the Negro may have been maintained by natural selection, offering as it does in the deep gloom of a tropical forest such singular advantages in war and the chase, and as a means of concealment from enemies; this is made more plausible by the fact that several tropical animals derive advantages from the possession of an identical color, the Elephant, for example, is stated to be difficult to discern although only a few feet distant, so closely does he harmonize with his surroundings.²

It might be further suggested that the color of the American Indian is in harmony with the color of his surroundings in the autumn, the season when he is most active in the chase, but this may be regarded as fanciful, as also the attempt to refer the pale races to the result of sexual selection guided by an appearance of cleanliness.

I venture the above at the risk of advancing what may have appeared in some of your writings which I have not seen.

Yours truly | Wm: B. Cooper

To Charles Darwin Esq: F.R.S.