But what I want to know is, how low in the scale sexual differences occur which require some degree of self-consciousness in the males, as weapons by which they fight for the female, or ornaments which attract the opposite sex. Any differences between males and females which follow different habits of life would have to be excluded. I think you will easily see what I wish to learn. A priori, it would never have been anticipated that insects would have been attracted by the beautiful colouring of the opposite sex, or by the sounds emitted by the various musical instruments of the male Orthoptera. I know no one so likely to answer this question as yourself, and should be grateful for any information, however small.
My second subject refers to expression of countenance, to which I have long attended, and on which I feel a keen interest; but to which, unfortunately, I did not attend when I had the opportunity of observing various races of man. It has occurred to me that you might, without much trouble, make a FEW observations for me, in the course of some months, on Negroes, or possibly on native South Americans, though I care most about Negroes; accordingly I enclose some questions as a guide, and if you could answer me even one or two I should feel truly obliged. I am thinking of writing a little essay on the Origin of Mankind, as I have been taunted with concealing my opinions, and I should do this immediately after the completion of my present book. In this case I should add a chapter on the cause or meaning of expression...
[The remaining letters of this year deal chiefly with the books, reviews, etc., which interested him.]
CHARLES DARWIN TO H. THIEL. Down, February 25, 1869.
Dear Sir,
On my return home after a short absence, I found your very courteous note, and the pamphlet ('Ueber einige Formen der Landwirthschaftlichen Genossenschaften.' by Dr. H. Thiel, then of the Agricultural Station at Poppelsdorf.), and I hasten to thank you for both, and for the very honourable mention which you make of my name. You will readily believe how much interested I am in observing that you apply to moral and social questions analogous views to those which I have used in regard to the modification of species. It did not occur to me formerly that my views could be extended to such widely different, and most important, subjects. With much respect, I beg leave to remain, dear Sir,
Yours faithfully and obliged, CHARLES DARWIN.
CHARLES DARWIN TO T.H. HUXLEY. Down, March 19 [1869].
My dear Huxley,
Thanks for your 'Address.' (In his 'Anniversary Address' to the Geological Society, 1869, Mr. Huxley criticised Sir William Thomson's paper ('Trans. Geol. Soc., Glasgow,' volume iii.) "On Geological Time.") People complain of the unequal distribution of wealth, but it is a much greater shame and injustice that any one man should have the power to write so many brilliant essays as you have lately done. There is no one who writes like you...If I were in your shoes, I should tremble for my life. I agree with all you say, except that I must think that you draw too great a distinction between the evolutionists and the uniformitarians.
I find that the few sentences which I have sent to press in the 'Origin' about the age of the world will do fairly well...
Ever yours, C. DARWIN.
CHARLES DARWIN TO A.R. WALLACE. Down, March 22 [1869].
My dear Wallace,
I have finished your book ('The Malay Archipelago,' etc., 1869.); it seems to me excellent, and at the same time most pleasant to read. That you ever returned alive is wonderful after all your risks from illness and sea voyages, especially that most interesting one to Waigiou and back. Of all the impressions which I have received from your book, the strongest is that your perseverance in the cause of science was heroic. Your descriptions of catching the splendid butterflies have made me quite envious, and at the same time have made me feel almost young again, so vividly have they brought before my mind old days when I collected, though I never made such captures as yours.