Beyond the publication of his work on the Beagle fishes, Jenyns continued his friendship and correspondence with Darwin.
Darwin drew upon Jenyns’s broad knowledge of natural history and frequently enquired about his observations on a particular topic, often relating to variations within and between species. Jenyns was even one of the recipients of a questionnaire, Questions About the Breeding of Animals , that Darwin issued in 1839. However, Jenyns was not an expert in selective breeding and it is not clear whether he replied.
Jenyns was one of the very few naturalists that Darwin trusted with the generalities of his evolutionary theories from quite early on in their conception. In a letter to Jenyns in 1844 he wrote:
The general conclusion, at which I have slowly been driven from a direct opposite conviction, is that species are mutable and that allied species are co-descendants of common stock … I shall not publish on this subject for several years.
Darwin to Jenyns, 12 October 1844
In his next letter to Jenyns, he defended this statement and hinted at the mechanism of natural selection:
A long searching amongst agricultural and horticultural books and people makes me believe (I well know how absurdly presumptuous this must appear) that I see the way in which new varieties become exquisitely adapted to the external conditions of life, and to other surrounding beings. – I am a bold man to lay myself open to being thought such a fool, and a most deliberate one.
Darwin to Jenyns, 25 November 1844
Darwin did not publish ‘On the Origin of Species by Means of Natural Selection’ for another fifteen years but when he did (24 November 1859), he was quick to seek Jenyns’s opinion:
My dear Jenyns
I must thank you for your very kind note forwarded to me from Down. I have been much out of health this summer & have been hydropathising here, for last six weeks with very little good as yet.— I shall stay here for another fortnight at least.
Please remember that my Book is only an abstract & very much condensed & to be at all intelligible must be carefully read. I shall be very grateful for any criticisms. But I know perfectly well that you will not at all agree with the lengths which I go. It took long years to convert me. I may of course be egregiously wrong; but I cannot persuade myself that a theory which explains (as I think it certainly does) several large classes of facts, can be wholly wrong; notwithstanding the several difficulties which have to be surmounted somehow, & which stagger me even to this day.
I wish that my health had allowed me to publish in extenso; if I ever get strong enough I will do so, as the greater part is written out, & of which M.S. the present volume is an abstract.—
I fear this note will be almost illegible; but I am poorly & can hardly sit up.
Jenyns was equally quick to read it and respond, supporting some aspects of the theory while challenging others, as can be seen from the transcribed letters reproduced below:
My dear Darwin
I have read your interesting book with all carefulness as you enjoined,—have gleaned a great deal from it, & consider it one of the most valuable contributions to Nat. Hist Literature of the present day. Perhaps you may like to know what I think of your particular theory, tho` you will doubtless have many opinions offered far more deserving to be weighed than mine.
As you are aware, I am no stickler for the multitude of so-called species created by so many naturalists of late years, & I always thought the time was not distant—when, after the brainsplitting process had been carried to it’s utmost length—some at least could see the necessity of retracing their steps, & again uniting a large number of the forms they had so carefully separated. But I frankly confess I did not look for any such large assemblages of species to be brought together in this way, as the descendants from one & the same stock, similar to what you have attempted in your volume. By this you will see that I embrace yr theory in part, but hardly to the full extent to which you carry it. Still I allow you have made out a very strong case, and I will not pretend to say what future researches in the same direction may not ultimately establish.
I can quite fall in with the view that those fossil animals which so closely resemble their living representatives at the present day, are in fact the progenitors of these last;—such indeed has been my opinion for many years, tho’ a contrary one, I know had been adopted by many of our first Geologists & Naturalists. I can also well believe that whole families have had a common parentage at some remote period of the past,—& that the same may have been the case, reasoning analogically (tho’ this is not always safe in Nat. Hist. speculations),—with groups of even higher denomination. But I cannot think that all the difficulties which stand in
the way of so extensive a generalization have been entirely got over—
One great difficulty to my mind in the way of your theory is the fact of the existence of Man. I was beginning to think you had entirely passed over this question, till almost in the last page I find you saying that `light will be thrown on the origin of man & his history’. By
this I suppose is meant that he is to be considered a modified & no doubt greatly improved orang! I doubt if this will find acceptance with the generality of readers— I am not one of those in the habit of mixing up questions of science & scripture, but I can hardly see what sense or meaning is to be attached to Gen: 2.7. & yet more to vv. 21. 22, of the same chapter, giving an account of the creation of woman,—if the human species at least has not been created independently of other animals, but merely come into the world by ordinary descent from previously existing races—whatever those races may be supposed to have been. Neither can I easily bring myself to the idea that man’s reasoning faculties & above all his moral sense, cd. ever have been obtained from irrational progenitors, by mere natural selection—acting however gradually & for whatever length of time that may be required. This seems to be doing away altogether with the Divine Image which forms the insurmountable distinction between man & brutes.
Jenyns to Darwin, 4 January 1860
My dear Jenyns
I am very much obliged for your letter. It is of great use & interest to me to know what impression my Book produces on philosophical & instructed minds. I thank you for the kind things which you say; & you go with me much further than I expected.— You will think it presumptuous, but I am convinced, if circumstances lead you to keep the subject in mind, that you will go further. No one has yet cast doubt on my explanation of the subordination of group to group, on homologies, Embryology & Rudimentary organs; & if my explanation of these classes of facts be at all right, whole classes of organic beings must be included in one line of descent.— The imperfection of the geological Record is one of greatest difficulties (by the way, Lyell, who is convert, does not think that I have exaggerated imperfection). During earliest period the record would be most imperfect, & this seems to me sufficiently to account for our not finding intermediate forms between the classes in the same great Kingdoms.—
It was certainly rash in me putting in my belief of probability of all beings having descended from one primordial form; but as this seems yet to me probable, I am not willing to strike it out.— Huxley alone supports me in this, & something could be said in its favour.—
With respect to man, I am very far from wishing to obtrude my belief; but I thought it dishonest to quite conceal my opinion.— Of course it is open to everyone to believe that man appeared by separate miracle, though I do not myself see the necessity or probability.—
Pray accept my sincere thanks for your kind note. Your going some way with me gives me great confidence that I am not very wrong. For a very long time I halted half-way; but I do not believe that any enquiring mind will rest half-way. People will have to reject all or admit all,—by all I mean only the members of each great Kingdom.—
My dear Jenyns
Yours most sincerely
Darwin to Jenyns, 7 January 1860
Despite not meeting in their later years, the warmth of feeling the two friends maintained can be seen in these extracts from the last letters they exchanged:
It must be a great satisfaction to you in the evening of life to think that your researches, so multifarious and at the cost of so much health and trouble have come at length to be duly appreciated; and that both you and your theories have outlived the fierce opposition that was made to them when you first set them before the scientific world. You, it appears, have just entered your 70th year. I, in a very little more than two months shall be entering my 78th … How few naturalists of the present day there must be who have known you longer than myself – or so long.
Jenyns to Darwin, 12 March 1877
Your extremely kind letter has given me warm pleasure. As one grows old one’s thoughts turn to the past rather than to the future, and I often think of the pleasant and to me valuable hours which I spent with you on the borders of the fens…
I suppose that I shall go on as long as I can without obviously making a fool of myself. I have a great mass of matter with respect to variation under nature, but so much has been published since the appearance of the Origin of Species, that I very much doubt whether I retain power of mind and thought to reduce the mass into a digested whole. I have sometimes thought that I would try, but dread the attempt.
Darwin to Jenyns, 13 March 1877