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C.D. Warner, et al., comp. The Library of the World’s Best Literature.
An Anthology in Thirty Volumes. 1917.

The Last Link

By Ernst Haeckel (1834–1919)

From an address to the Fourth International Congress at Cambridge, England, delivered on August 26th, 1898, ‘On Our Present Knowledge of the Descent of Man’

THE DIRECT descent of man from some extinct ape-like form is now beyond doubt, and admits of being traced much more clearly than the origin of many another mammalian order. The pedigrees of the Elephants, the Sirenia, the Cetacea, and, above all, of the Edentata, for example, are much more obscure and difficult to explain. In many parts of their organization—for example, in the number and structure of his five digits and toes—man and monkeys have remained much more primitive than most of the Ungulata.

The immense significance of this positive knowledge of the origin of man from some Primate does not require to be enforced. Its bearing upon the highest questions of philosophy cannot be exaggerated. Among modern philosophers no one has perceived this more deeply than Herbert Spencer. He is one of those older thinkers who before Darwin were convinced that the theory of development is the only way to solve the “enigma of the world.” Spencer is also the champion of those evolutionists who lay the greatest weight upon progressive heredity, or the much combated heredity of acquired characters. From the first he has severely attacked and criticized the theories of Weismann, who denies this most important factor of phylogeny, and would explain the whole of transformism by the “all-sufficiency of selection.” In England the theories of Weismann were received with enthusiastic acclamation, much more so than on the Continent, and they were called “Neo-Darwinism,” in opposition to the older conception of Evolution, or “Neo-Lamarckism.” Neither of those expressions is correct. Darwin himself was convinced of the fundamental importance of progressive heredity quite as much as his great predecessor Lamarck; as were also Huxley and Spencer.

Three times I had the good fortune to visit Darwin at Down, and on each occasion we discussed this fundamental question in complete harmony. I agree with Spencer in the conviction that progressive heredity is an indispensable factor in every true monistic theory of Evolution, and that it is one of its most important elements. If one denies with Weismann the heredity of acquired characters, then it becomes necessary to have recourse to purely mystical qualities of germ-plasm. I am of the opinion of Spencer, that in that case it would be better to accept a mysterious creation of all the various species as described in the Mosaic account.

If we look at the results of modern anthropogeny from the highest point of view, and compare all its empirical arguments, we are justified in affirming that the descent of man from an extinct Tertiary series of Primates is not a vague hypothesis, but an historical fact.

Of course, this fact cannot be proved exactly. We cannot explain all the innumerable physical and chemical processes, all the physiological mutations, which have led during untold millions of years from the simplest Monera and from the unicellular Protista upwards to the chimpanzee and to man. But the same consideration applies to all historical facts. We all believe that Aristotle, Cæsar, and King Alfred did live; but it is impossible to give a proof within the meaning of modern exact science. We believe firmly in the former existence of these and other great heroes of thought, because we know well the works they have left behind them, and we see their effects in the history of human culture. These indirect arguments do not furnish stronger evidence than those of our history as vertebrates. We know of many Jurassic mammals only a single bone, the under jaw. We all believe that these mammals possessed also an upper jaw, a skull, and other bones. But the so-called “exact school,” which regards the transformation of species as a hypothesis not proven, must suppose that the mandibula was the only bone in the body of these curious animals.

Looking forward to the twentieth century, I am convinced that it will universally accept our theory of descent, and that future science will regard it as the greatest advance made in our time. I have no doubt that the influence of the study of anthropogeny upon all other branches of science will be fruitful and auspicious. The work done in the present century by Lamarck and Darwin will in all future times be considered one of the greatest conquests made by thinking man.