“Sir William Thompson has lately advanced arguments from three distinct lines of inquiry agreeing in one approximate result. The three lines of inquiry are—(1) the action of the tides upon the earth’s rotation; (2) the probable length of time during which the sun has illuminated this planet; and (3) the temperature of the interior of the earth. The result arrived at by these investigations is a conclusion that the existing state of things on the earth, life on the earth, all geological history showing continuity of life, must be limited within some such period of past time as one hundred million years. The first question which suggests itself, supposing Sir W. Thompson’s views to be correct, is: Has this period been anything like enough for the evolution of all organic forms by ‘natural selection’? The second is: Has the period been anything like enough for the deposition of the strata which must have been deposited if all organic forms have been evolved by minute steps, according to the Darwinian theory?” (“Genesis of Species,” p. 154).
Mr. Mivart then quotes from Mr. Murphy—whose work I have not seen—the following passage:—
“Darwin justly mentions the greyhound as being equal to any natural species in the perfect co-ordination of its parts, ‘all adapted for extreme fleetness and for running down weak prey.’ Yet it is an artificial species (and not physiologically a species at all) formed by a long-continued selection under domestication; and there is no reason to suppose that any of the variations which have been selected to form it have been other than gradual and almost imperceptible. Suppose that it has taken five hundred years to form the greyhound out of his wolf-like ancestor. This is a mere guess, but it gives the order of magnitude. Now, if so, how long would it take to obtain an elephant from a protozoon or even from a tadpole-like fish? Ought it not to take much more than a million times as long?” (“Genesis of Species,” p. 155).
I should be very sorry to pronounce any opinion upon the foregoing data; but a general impression is left upon my mind, that if the differences between an elephant and a tadpole-like fish have arisen from the accumulation of small variations that have had no direction given them by intelligence and sense of needs, then no time conceivable by man would suffice for their development. But grant “a little dose of reason and judgement,” even to animals low down in the scale of nature, and grant this, not only during their later life, but during their embryological existence, and see with what infinitely greater precision of aim and with what increased speed the variations would arise. Evolution entirely unaided by inherent intelligence must be a very slow, if not quite inconceivable, process. Evolution helped by intelligence would still be slow, but not so desperately slow. One can conceive that there has been sufficient time for the second, but one cannot conceive it for the first.