human
For so long as the rate of growth continues rapid, there is proof that the organism gets food with facility--that expenditure does not seriously check assimilation; and that the size reached is as yet not disadvantageous: or rather, indeed, that it is advantageous. But when the rate of growth is much decreased by the increase of expenditure--when the excess of assimilative power is diminishing so fast as to indicate its approaching disappearance--it becomes needful, for the maintenance of the species, that this excess shall be turned to the production of new individuals; since, did growth continue until there was a complete balancing of assimilation and expenditure, the production of new individuals would be either impossible or fatal to the parent. And it is clear that 'natural selection' will continually tend to determine the period at which gamogenesis commences, in such a way as most favours the maintenance of the race.