Put as I have just put it, and as it used to be put in all the old-fashioned textbooks of Mr. Wells’s youth, it sounds not only simple, but convincing It is when one looks into what it implies that the old Darwinian theory of Natural Selection gets shaky.
THE IMPLICATIONS OF NATURAL SELECTION
(1) In the first place, note that, according to this theory, there can be no stable type; there can be no fixity of species. All is in flux. Environment is never exactly the same, even for two days at a time, let alone for two successive thousand years. Very long slow changes in climate, or any other factor of environment, would necessarily involve long, unceasing, slight transformation, never halting. The theory necessarily demands a living world in a state of slow but incessant transformation, with no fixed mature results at the end of development.
It is only by the loosest sort of thinking, and by substituting imagination for close reasoning, that the ideas of Natural Selection and permanent stable types can be reconciled.
Thus some have said that the Seal was “sifted out” by Natural Selection, got more and more suited to its habitat by “survival of the fittest,” until it had no further need for adaptation: it was at last perfectly adapted to the purposes of its life.
Well, one of the most pressing needs of the seal under the conditions of its life is to scramble on to the icefloes in order to escape from its most deadly enemy. It does so most clumsily and ineffectually by the help of its flappers. For countless generations Natural Selection has had time to work if it were capable of bettering that state of affairs by producing flappers more serviceable. It has not done so. Why? Not because the seal is “in equilibrium,” but because, however it may have evolved, it is now a fixed type: mature: it is what is and can now no longer change its fundamental structure.
It is true that Darwin and others talk vaguely of the process “reaching equilibrium,” but that, according to his own theory, is a contradiction in terms. Under Natural Selection there can be none such.
Darwin, Wallace, and the rest did not think clearly enough to see that this was so, but so it is. If a hare runs fast because it has developed its speed through an immense series of faster and faster hares who “survived” because their speed made them “fitter” to escape enemies, then the process demands that the speed shall continually increase. Your hare of 1925 that can cover the measured mile in three and a half must develop into your hare of A.D. 20,000 who can cover it in three: for there is no doubt whatsoever that an increase of speed has survival value. And he must be developing all the time. There is no escape from that conclusion, if the theory of Natural Selection held water: which it doesn’t.
That is the first necessary result of Natural Selection. If the theory of Natural Selection is true there are not now, and cannot have been in the past, fixed types recognizable by marked and permanent characters.
(2) Next, observe that the theory of Natural Selection also demands a regular progression, and a very slow one. It involves, for instance, the development of a land animal out of a water animal by an immense accumulation of exceedingly slight differences in each generation, favourable to a water animal’s longer and longer bouts of staying out of water. These exceedingly slight differences in each generation are presupposed to be only such as we always observe between parent and child. Darwinian Natural Selection as a prime cause can admit no rapid, startling changes.