CANON TRISTRAM THE FIRST PUBLICLY TO ACCEPT THE THEORY OF NATURAL
SELECTION (1859).
Although the historic meeting at the Linnean Society appeared to
produce but little effect, one distinguished naturalist publicly
accepted the theory of natural selection before the publication of “The
Origin of Species,” and therefore as the direct result of Darwin’s
and Wallace’s joint paper. This great distinction belongs to Canon
Tristram, as Professor Newton has pointed out in his Presidential
Address to the Biological Section of the British Association at
Manchester in 1887 (“Reports,” p. 727), at the same time expressing the
hope “that thereby the study of Ornithology may be said to have been
lifted above its fellows.”
[Sidenote: CANON TRISTRAM’S SUPPORT.]
Canon Tristram’s paper, “On the Ornithology of Northern Africa” (Part
iii., The Sahara, continued), was published in _The Ibis_, vol. i.,
October, 1859. The important conclusions alluded to above are contained
at the end of the section upon the species of desert larks (pp.
429–433):
“Writing with a series of about 100 larks of various species from
the Sahara before me, I cannot help feeling convinced of the
truth of the views set forth by Messrs. Darwin and Wallace in
their communications to the Linnean Society, to which my friend
Mr. A. Newton last year directed my attention.... It is hardly
possible, I should think, to illustrate this theory better than
by the larks and chats of North Africa. In all these birds we
trace gradual modifications of coloration and of anatomical
structure, deflecting by very gentle gradations from the ordinary
type; but when we take the extremes, presenting most marked
differences.”
These differences, he concludes--
“have a very direct bearing on the ease or difficulty with which
the animal contrives to maintain its existence.”
He then points out, upon the uniform surface of the desert it is
absolutely necessary that animals shall be protected by their colour:
“Hence, without exception, the upper plumage of every bird,
whether Lark, Chat, Sylvian, or Sandgrouse, and also the fur
of all the small mammals, and the skin of all the Snakes and
Lizards, is of one uniform isabelline or sand colour. It is
very possible that some further purpose may be served by the
prevailing colours, but this appears of itself a sufficient
explanation. There are individual varieties in depth of hue among
all creatures. In the struggle for life which we know to be going
on among all species, a very slight change for the better, such
as improved means of escaping from its natural enemies (which
would be the effect of an alteration from a conspicuous colour
to one resembling the hue of the surrounding objects), would
give the variety that possessed it a decided advantage over the
typical or other forms of the species. Now in all creatures,
from Man downwards, we find a tendency to transmit individual
varieties or peculiarities to the descendants. A peculiarity
either of colour or form soon becomes hereditary when there
are no counteracting causes, either from change of climate or
admixture of other blood. Suppose this transmitted peculiarity
to continue for some generations, especially when manifest
advantages arise from its possession, and the variety becomes not
only a race, with its variations still more strongly imprinted
upon it, but it becomes the typical form of that country.”
Canon Tristram then points out the manner in which he imagines that one
of the crested larks of the desert has been produced by the survival
of the lightest coloured individuals, _Galerida abyssinica_ only
differing in this respect from _G. cristata_ of Europe. Short-billed
species of the same genus inhabiting hard rocky districts, and
long-billed inhabiting loose sandy tracts have, he believes, been
produced by the survival in each case of the forms of bill most suited
to procure food:
“Here are only two causes enumerated which might serve to
_create_ as it were a new species from an old one, yet they
are perfectly natural causes, and such as, I think, must have
occurred, and are possibly occurring still. We know so very
little of the causes which in the majority of cases make
species rare or common, that there may be hundreds of others
at work, some even more powerful than these, which go to
perpetuate and eliminate certain forms ‘according to natural
means of selection.’ But even these superficial causes appear
sufficient to explain the marked features of the Desert races,
which frequently approach so very closely the typical form, and
yet possess such invariably distinctive characteristics, that
naturalists seem agreed to elevate them to the rank of species.”
Although the author also declares his belief in the special creation
of many species--a view put forward as possible by Darwin in the
“Origin”[G]--and also believed in some direct influence of locality,
climate, etc., the above quoted passages are a most complete acceptance
of natural selection, at the same time affording excellent examples of
its operation.