Complex now, but how much simpler and more intelligibly organised may it not become in another hundred thousand years? Or in twenty thousand?  For man at present believes that his interest lies in that direction; he spends an incalculable amount of labour and time and thought in making machines breed always better and better; he has already succeeded in effecting much that at one time appeared impossible, and there seem to be no limits to the results of accumulated improvements if they are allowed to descend with modification from generation to generation.

It must always be remembered that man's body is what it is through having been moulded into its present shape by the chances and changes of many millions of years, but that his organisation never advanced with anything like the rapidity with which that of the machines is advancing.