In man only we discover none of these partial adaptations, further than that he is intended to exist upon the ground; and the human race alone, in opposition to all other animals, takes cognisance of the progressive changes adverted to, and, from reflection, intentionally opposes obstacles to their course, or systematically endeavours to divert their energy. Man's agency, indeed, tends everywhere to alter, rather than to preserve, the indigenous features of a country', those features which natural causes combine to produce: in short, he strives against the united efforts of all other agents, insomuch that, wherever he appears, with his faculties at all developed, the aspect of the surface becomes changed: forests yield to his persevering labours; the marshes are drained, and converted into fertile lands; the very climate, accordingly, changes under his influence, which every way inclines to extirpate the indigenous products of the soil, or to reduce them, by domestication, to a condition subservient to the promotion of human interests.
Does not, then, all this intimate that, even as a mundane being, man is no component of that reciprocal system to which all other species appertain? a system which for countless epochs prevailed ere the human race was summoned into being. His anomalous interference, therefore (for this work most aptly expresses the bearings of human influence upon that system), essentially differing from the uniform agency of all the rest, in not conducing to the general welfare, is thus shown to be in no way requisite to fill a gap in the vast system alluded to.
All rather tends alike to indicate him a being of diverse, of higher destiny; designed, in the course of time, with the aid of physical causes ever in operation, and the presumed cessation of the creative energy, to revolutionise the entire surface of our planet.
I will presently recur to this subject as regards marine productions. It is sufficiently evident, that, as the human species is bound to no description of locality, but alike inhabits the mountain and the plain, and is, by self-contrivance, enabled to endure the fervid heats of tropical climes, equally with the withering blasts of a polar winter, it is consequently proof against the undermining effects of those surface changes which suffice to effect the extermination of every other.13 Its future removal, then, from this scene of existence, whenever that shall happen, will probably be brought about on another principle: how, it would be most useless to inquire.
There is no reason, however, hence to anticipate that supernatural means must necessarily be resorted to, as a malignant disease might suffice to level all ranks in the dust. It is enough for my present purpose, to indicate in this the diversity of the human from all other species.
Some have argued the connection of man with the reciprocal system to which the inferior animals pertain, because, forsooth, he sometimes is annoyed by parasites. Without dwelling upon this topic, I may be allowed to say that it remains to be shown that any are peculiar to the human species. The certain fact, that different races of mankind are infested by distinct species, rather points to the conclusion, that, as the bed cimex can subsist and thrive away from human habitations, so also may even those species which abide on the person.14
I will now proceed to notice, and follow to its bearings, that mysterious impulse (if possible, even more incomprehensible than ordinary instinct) which guides a migrant animal to its destined haven; which also propels a bee towards its hive, and a pigeon homeward from one extremity of Europe to another; a principle, as will be shown, not wholly absent from the human constitution. The migrative restlessness displayed so forcibly by birds of passage, even when raised in confinement, and plentifully supplied with the nourishment they have been accustomed to (thus showing that insufficiency of food is not the predisposing cause, as is also intimated by the early departure of certain species from their summer haunts, after performing the duties of the season), is merely on a par with all other instinctive manifestations : and I may cursorily remark that, from much careful and attentive observation, I have determined, at least to my own satisfaction, that, as a general rule, it is in autumn mainly influenced by decline of temperature, and in spring by the breeding stimulus : the period of the incidence of which latter (though, undoubtedly, somewhat affected by temperature) is primarily dependent on specific peculiarity, and, secondarily, on constitutional vigour.15
It is not the erratic impulse, however, so much as the guiding principle, that we have here to do with; that wonderful, most inexplicable principle, on which a diurnal migratory bird is not only, and by night, enabled to soar for even thousands of miles, over seas and continents, surmounting every obstacle, even lofty mountain ridges, in its course, impelled always in one unvarying direction, till it arrives at the proper winter quarters of its species; but, at the ensuing season, is also led back to its former abode, to the precise locality that it had previously set out from, having been known even to return to confinement. I conceive it unnecessary to detail observed instances of this astonishing fact, because, in the feathered race, it is well known to every student of natural history. It will be enough to mention, that I have an instance, on indisputable authority, of a lame redstart returning regularly for sixteen summers to the same garden.
Among mammalians, numerous instances have been recorded, resting on unexceptionable testimony, of animals returning straight to their accustomed haunts, over pastures and across streams they could not possibly have ever traversed before, and by a nearer and very different route from that by which they had been driven or carried. To these I will add the following, which occurred to the personal knowledge of my informant. A cat, from the centre of an intricate and populous seaport town,16 was shipped on board of a vessel bound for the Brazils; and, after performing the voyage to and fro, contrived to escape, on returning to its native port, and found its way, through several streets to its former domicile.
Mr. Jesse, in the third series of his Gleanings, has related a like anecdote of a reptile. Of a number of turtles, captured on Ascension Island, chanced to be an individual which, to use the technical phrase, had lost one of its fins. It was marked in the ordinary manner on the under shell, which marks are well known to be indelible. The vessel, on arriving in the Channel, was long detained by contrary winds, during which time a great mortality took place among the turtles; these dying one after another so fast, that it was at length resolved to cast what few remained of them, including the lame one, into the sea, to give them, as was said, a chance for their lives. Three years afterwards, this same turtle, with its three fins, and the marks of the hot iron beneath, was found again upon Ascension Island.
It is sufficient to refer to the results of numerous experiments which have been instituted on the fry of the Salmonidae, to be convinced of the prevalence of the same surprising impulse also among fishes.Click here to go to Psychological Distinctions Between Man and Other Animals - Part 4
13. There is no occasion, here, to follow out all the causes which combine to bring about the extirpation of species; but I
will mention one which appears not to have been duly considered by those who have written on the subject. We have
every reason to believe that the original germ of an animal may be developed into either male or female; and it is certain
that external circumstances exercise a very considerable influence in determining the sex of the future being. Now, the
results of experiments instituted on sheep by the Agricultural Society of Severac fully warrant the conclusion, that, where
species exist under circumstances favourable for their increase, a greater number of that sex is produced, which, in
polygamous animals is most effectual for their multiplication; whereas the contrary obtains, probably, in proportion to
the difficulty of obtaining a livelihood. The relative age and constitutional vigour of the parents is likewise an important
element in this problem; and, combined with the former, will enable us to calculate an average with tolerable precision.
I have collected some very curious facts bearing upon this subject, some of which are extremely difficult of explanation.
Mr. Knapp, in his Journal of a Naturalist, has the following, which is worthy of close attention: "The most remarkable
instance," he observes, of variation in the relative proportion of the sexes, "that I remember of late, happened in 1825.
How far it extended I do not know. but, for many miles round us, we had in that year scarcely any female calves born.
Dairies of forty or fifty cows produced not more than five or six; those of inferior numbers in the same proportion; and
the price of female calves for rearing was greatly augmented. In a wild state," he justly observes, "an event like this
would have considerable influence upon the usual product of some future herd" (note to p. 138).
This occurred in Gloucestershire. The character of the preceding season is not stated; but, most probably, it was one
of scarcity to the parent animals. The following list exhibits the proportion of the sexes in the annual produce of
generally six cows, of the Ayrshire breed (four being the same individuals throughout, the remainder their produce),
kept in a park in this neighbourhood. It commences with the year in which the present superintendent took charge of
the stock; and there is no question but that, if the stock-books of other persons who have the care of cattle were to be
duly looked over for a series of years, many similar and equally interesting facts would be brought to light.
In 1826 from 6 cows, were born 6 male calves, 0 females. 1827 " 6 " " " 6 " " 0 " 1828 " 6 " " " 4 " " 0 " 1829 " 5 " " " 3 " " 1 " 1830 " 6 " " " 0 " " 3 " 1831 " 5 " " " 0 " " 5 " 1832 " 5 " " " 0 " " 5 " 1833 " 6 " " " 0 " " 6 " 1834 " 6 " " " 0 " " 6 " 1835 " 6 " " " 3 " " 3 " 1836 " 6 " " " 2 " " 4 "Thus it appears that, for the first four years, but one female calf was produced out of twenty-three births; that in the