There is also a bass-relief from the ruins of Babylon, with a dog represented upon it, which is found by naturalists to be identical with a species of the dog existing in Asia at the present day.
Evidence of Fossil Remains
But we have still more conclusive evidence than this derived from ancient monuments of the very great permanence of the characteristics by which different species of plants and animals are distinguished from each other, in the fossil remains which exist in the strata of the earth. By means of these our observations upon the forms of vegetable and animal life which have existed upon our globe may be carried back to an immense antiquity, and extended over so vast a number and variety of species as to furnish us, as it has always been supposed, with all the means of information on this subject that can be desired. It has been thought to be fully proved by these observations that every species which exists upon the earth remains unchanged so long as it exists. When at length its period has expired, it disappears from the field, while new ones are continually arising to take the place of those that are gone. But no one passes, by gradations, into any other; and the lines of distinction by which each is separated from all the rest remain sharp and well-defined from the beginning to the end.
Opinions of Naturalists and Philosophers
At least, this has been hitherto the view which naturalists and philosophers have almost unanimously taken of this subject, though there have not been wanting writers who have maintained the contrary opinion. Notwithstanding the evidence furnished by the appearance of fossil remains, that the lines of demarcation separating the different species are absolutely and forever impassable, there have been some advocates of the theory that all the present races of animals may have been derived by insensible gradations from a few primordial types. This theory has very recently been brought forward anew in a form to attract general attention. Still, so unanimous and so decisive has been the testimony of geologists in respect to the evidence furnished by the fossil remains, and so inconsistent is it with the development theory, as it is called, that very great changes must take place in the opinion of naturalists in respect to the true import of the geological records before this opinion can be generally received.
But however the great question in respect to the absolute and perpetual permanence of the distinction of species may be ultimately decided, there is no doubt that all naturalists fully concur in the opinion that this permanence is, at all events, so great as entirely to preclude the possibility that the American species of plants and animals can have descended from the stocks of the old world within so short a period as six thousand years. Some other supposition must, therefore, be made than that the forms of life existing here could have been derived, within that period, by ordinary generation from those prevailing in other portions of the world. Some of the principal suppositions which have been made will be presently alluded to.
Examples of Diversity
Some of the American plants and animals attracted great attention in Europe when they were first made known there, being recognized as entirely new, and found to be quite peculiar in character. The potato was one; the turkey was another. No turkey was ever known to exist in Europe, Asia, or Africa before that time, and no fossil remains of such an animal have ever been discovered there. The tobacco plant was another species that was originally first found in America, though it has since become extensively diffused throughout the world. A more particular account of some of these plants and animals will be given in future chapter. They are only mentioned here as illustrations of the great truth, that when this country was first explored by European visitors an entirely new series of forms of vegetable and animal life was found to prevail here, and such as could not have resulted from any of the forms that prevail in the old world, within the period of six thousand years, through the operation of any laws that are known to us, in respect to the relation of parent and offspring.
The General Types the Same
And yet, though the plants and animals that are found in America are all different, and seem to be essentially different, so far as relates to derivation from the same parentage within any moderate period, from those of the old world, it is a very curious and a very significant fact, that there is a very close analogy between the two great stocks - an analogy so close as to furnish very strong reason to believe that they must have had a common origin, or at least have derived their existence from some common law. All, or nearly all, the great types of animal and vegetable life which are known in the old world, have their representatives in the new, and yet no particular species are so represented. While there is a generic similarity, there is also a specific difference. We scarcely knew which excites most our wonder and curiosity, the analogy in the great types, or the total, or almost total diversity in individual species. We say almost total, for, in addition to the exceptions already referred to, by the time that the fauna and flora of America came to be fully examined, great numbers of animals had been brought over, either by accident or design, from Europe, and mingled with the animals in America; and there are many plants which are now found growing wild in various parts of the country, and seem to be natives, but which are identical in species with those growing in Europe. It is inferred in such cases that the seeds were originally brought from the old world, though perhaps it cannot in all cases be positively proved that they were. It may however be said with certainty, that, as a general rule, of
Lammergeyer of the Alps
the hundreds and thousands of plants and animals, natives of America, that have been examined and described, all or nearly all are essentially different from those of corresponding type produced by the old world.
The accompanying engravings, which represent the gigantic vultures which inhabit the mountain summits respectively of the new world and the old, strikingly illustrated this principle. While they are generically similar, both in their structure and in
Condor of the Andes
their habits, still, in respect to what the naturalists call specific characters, they are entirely distinct.
The Mystery General
The mystery which attends the origin of these different and peculiar species of plants and animals inhabiting the new continent, has been found, since America was discovered, to be general, for it is now known that not merely America, but also every part of the globe, so far as the different zones and districts of the earth are separated from each other by seas, or mountains, or other great natural boundaries, has each its own fauna and flora different from those of every other region. These differences of species, too, exist not in space only, but in time. From the evidence that an examination of the strata of the earth affords, we find that every different period of the earth's history, going back to very remote ages, had its own system of plants and animals, so that thousands of species that existed once do not exist now, and those which exist now did not exist then. Thus it is established by evidence that seems to be conclusive, that just as in the history of any one species, there is a succession of individuals, each of which is born, grows, flourishes, declines, and dies, to be succeeded by others which rise into being, and come forward to maturity, while their predecessors decline; in the same manner, in the history of the world, there has been a succession of species. each of which has come into being in its own time, increased in numbers, become widely extended, and then has gradually diminished and finally. disappeared, to be succeeded by other species that arise in the same manner, and go through in the same manner the successive periods of youth, maturity, and decay. Thus it would appear that, of the vast congeries of animal and vegetable creations which the history of the globe presents to view, each separate period of its existence, and also every different district on its surface, has received its own peculiar and exclusive forms. There are several different opinions in regard to the proper explanation of this remarkable fact. Of these opinions only two are now seriously entertained by naturalists and philosophers, and the question between these two is, at the present time, a subject of earnest discussion throughout the whole scientific world.