The human species

by A. de Quatrefages

II. But, as I said before, this harmony is scarcely ever obtained without struggles and sacrifices. In this respect again man resembles plants and animals. Let us see, in the first place, what may be learnt on this subject from these beings of inferior organisation.

It is well known that two kinds of wheat are recognised by agriculturalists, one of which is sown in spring and the other in autumn, both being reaped at about the same time. It is evident that the conditions of development are very different in the two cases. To sow a spring wheat in autumn, was, so to speak, changing the condition of existence, and, consequently, attempting an experiment in acclimatisation. This was done by the celebrated Abbé Tessier. A hundred seeds of autumn wheat were sown in spring; they all came up and produced young plants, which passed through the usual stages of vegetation. Only ten plants, however, formed seeds, which only ripened upon four plants. A hundred seeds of this first crop produced fifty fertile plants. In the third generation the hundred seeds produced corn. The inverse experiment gave similar results.

The acclimatisation of wheat at Sierra Leone offers still more instructive peculiarities. The first year almost all the seed ran to leaf; the ears were very few, and poorly filled. The seeds of this first crop were sown; a great number did not come, up at all. Those which survived were a little more fertile. Much patience was, however, required, and many generations passed before normal crops were obtained. We see that in Tessier’s experiment all the seeds of wheat and their germs lived, but the grain was wanting, or was more or less abortive. There was, then, a loss of generations. The same thing occurred at Sierra Leone. Moreover, the second time the seed was sown, some of it never came up at all. Here, therefore, the loss of individuals was added to that of generations.

The history of our poultry which has been imported into America, presents equally significant facts. At Cuzco the broods are just as large as in Europe. Garcilasso de la Véga tells us, however, that in his time the eggs were few, and the chickens difficult to rear. The species has, since then, become acclimatised.

When M. Roulin made his observations upon the geese imported into Bogota, it was more than twenty years since they had been first brought to that high plateau, and, even then, they had not attained their normal fecundity. They were not, however, far from it, while at first the eggs were very rare. A quarter, at the most, of the eggs were hatched, and half the goslings died before the end of the first month. Thus, on the one hand, the Bogota breeder did not obtain nearly as many eggs as he would have done in Europe, while, on the other hand, at the end of a period scarcely equal to the two-hundredth part of the life of the goose, he obtained from these eggs scarcely one-eighth of what they would have produced in Europe.

The history of these Bogota geese is most instructive. At the outset we meet with all those circumstances which would seem to justify us in the prediction of a failure. The infertility of the females, as attested by the rarity of the eggs, and that of the males, as shown in the strong proportion of addle eggs, point to a serious physiological injury to the organs whose action alone insures the permanence of the species. The enormous mortality among the young birds betrayed a no less serious alteration in the components of individual life. Nevertheless, at the time of M. Roulin’s journey, acclimatisation had been almost realised, and must without doubt now be completed.

More than twenty years were, however, necessary for the organisation of this European bird to establish a harmony between itself and the conditions of existence on the high plateaus of America. The breeders were consequently forced to submit to many losses, affecting both generations and individuals.

We see what took place in the case of the fowls and geese as well as in that of the wheat. Shortly after their emigration the climate killed all those who were unable to conform to the new exigencies. A certain number offered sufficient resistance to live almost as long as they would have done under their natural conditions of existence; but their weakened organisation was unfitted for generation, or could only produce beings which at once succumbed. Through all these disasters, however, a few privileged organisations conformed, from the first, more or less to the new exigencies. With slight modifications they transmitted their own acquirements combined with the suitable aptitudes to their progeny, who in turn made further advances in the direction opened by their parents; and from year to year the adaptation was more complete, the acclimatisation more nearly realised.

But it is evident that years here represent generations. It is only from parent to offspring, through heredity and accumulation, that the living being becomes modified, and by degrees harmonises with the conditions of life. When, however, we are no longer studying an animal, plant, or a bird, which has the faculty of yearly reproduction, but species or races of a more tardy reproduction, we must remember that it is necessary to reckon by generations, and not by years.

III. Such are the data by which we are enabled to judge of the attempts at acclimatisation made by man himself. I cannot too often repeat the fact that, in common with organised and living beings, we are subject to all the general laws which govern life and organisation in animals and plants. Our intelligence is unquestionably of assistance to us in our struggles with nature, but, unfortunately, the power which we derive from her is limited, and in no case are we placed at greater disadvantage than in the increasing struggle demanded by a considerable change in conditions of life. The most ingenious efforts are then unable to free man from vicissitudes more or less analogous to those suffered by the wheat of Sierra Leone, the fowls at Cuzco, and the geese at Bogota.