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Darwin Correspondence Project

From William Main   2 April 1873

New Ferry Park | Birkenhead

2d. April | 1873

Dear Sir

A short time ago I took the liberty of writing you regarding a theory I had that expression was the result of the direction of lines—1 You courteously replied, remarking that I would find it difficult to account for all the cases in your book on this ground; & that even if I could do so, how was it to be explained?—2 After reading your book on expression3 carefully, I still find that there is a very large amount of truth in the theory— At first I feared that the evidence such as it was, bore against the theory of evolution & in favour of the separate creation doctrine— But after more careful consideration it appears to me that the facts may be quite easily accounted for on the principle of inheritance— Our progenitors must have seen that all young plants when growing, were erect, as a general rule, whereas when dying their heads drooped; that young forest trees were erect, but when old their branches also drooped; that animals generally when full of life & energy showed uptending lines, while weak & dying animals showed the reverse both in their forms & faces— seeing these & thousands of other instances of the effect of up & down lines, our ancestors would no doubt come by experience to associate energy & progress with up lines; & sadness & decay with the reverse—

By inheritance these associations have become instinctive in us— This being the case regarding up & down tending lines, the horizontal line would soon come to indicate repose on the same grounds—

Animals being guided by a brain, the whole muscular system acts in concert & shows up lines when the nerves are excited & the muscles in a state of tension; & when on the contrary the nerves are unstrung & the muscles relaxed down lines are produced.

Hence there is harmony of lines in whatever state the animal may be & by inherited knowledge we feel this instinctively— Whenever a disharmony of lines is observed therefore, we are struck by the incongruity—e.g. when a dog darts off in a curve with his tail down & hind quarters crouching, while his forequarters are raised & his ears & facial muscles at rest— Again when a man shrugs his shoulders, the eye brows are raised, & the mouth angles depressed; the head is tilted downwards to one side, & the shoulders are raised; the upper arm is drooping close by the side, & the fore-arm & fingers are spread out at right angles to the body—the whole powerfully expressing a puzzled state— The same disharmony of lines is often observed in the face of a drunk man, & in all these cases a mere infant of two years of age will laugh at the sight, or feel uneasy at the incongruity.

On enquiring into the source of expression in sounds I think that plaintive & joyful sounds may be accounted for in a similar way— The first can be produced by little muscular energy, the second requires much. All animals when mourning utter plaintive sounds—e.g. the Blackbird when its nest is disturbed &c. So all animals when in slight pain or unhappiness, if they give forth sounds at all, these are either doleful or plaintive on account of the little energy called up— If pain is so severe as to call forth full energy, then the sound is piercing & unpleasant— Dr. Seemann’s remark on the language of Music in the East (Descent of Man vol 2. P. 334) is no doubt quite against this interpretation of sounds in that part of the world;4 but notwithstanding Dr. S’s remarks, with Animals & Birds in general the above remarks are so universal that our progenitors would soon come to associate plaintive sounds with sadness & weakness, & the sounds of joy with energy—

The cause of harmony in sounds I do not at all understand, but the harmony of lines may perhaps throw some light on the question in the hands of one who thoroughly understood the theory of music.

This instinctive knowledge of sounds & lines has no doubt come to us by inheritance, but it is not always true—e.g. the weeping ash has great energy of growth; & again, we have no reason to believe that the Bullfinch & woodpigeon are melancholy birds, though the call of the one & the coo of the other are sad to our ears—

The fact that dogs, monkeys, & other animals as well as Birds possess this instinctive knowledge is clearly another small link in the great chain of proof which you are so nobly working out that we have all a common origin—

I trust that the interest you show in all matters which bear on the theory of evolution will excuse my troubling you with so long a letter—

I am | Yours faithfully | Wm. Main

To | C. Darwin Esqr. | Down | Kent


In Descent 2: 334, CD had quoted Berthold Carl Seemann’s remark that, travelling eastwards, one found a different language of music. Seemann also noted that although Western music employed major keys for joyful songs, minor keys were used for these in the East.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Descent: The descent of man, and selection in relation to sex. By Charles Darwin. 2 vols. London: John Murray. 1871.

Expression: The expression of the emotions in man and animals. By Charles Darwin. London: John Murray. 1872.


Having now read Expression, WM repeats his criticism of "antithesis". Explains his theory of up-and-down-tending lines.

Letter details

Letter no.
William Main
Charles Robert Darwin
Sent from
Source of text
DAR 171: 28
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 8836,” accessed on 6 December 2021,

Also published in The Correspondence of Charles Darwin, vol. 21