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Saturday, November 22, 2014


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The Vegetable In The Witness Box
By Islip Collyer, 1922



The objection to Evolution under the heading of Dilution may be very simply stated. Even if it be admitted that chance variations would occur in the manner claimed and that natural selection would tend to develop and perfect them, such profitable variations would at once be diluted and checked by interbreeding between animals which varied and animals which did not, or by cross breeding between creatures whose slight variations were developed in different directions and would thus neutralise each other. When it is remembered how difficult stock breeders find it to make permanent the variations they have selected, and how readily these slight differences are lost by breeding with the old stock, it must be admitted that the law of dilution presents a serious problem to the exponent of Evolution.

Darwin recognised the force of dilution and made some important admissions regarding it. He stated


his conviction that abrupt variations occurring in single individuals would be lost by dilution, and that this actually occurs under domestication unless man takes pains to isolate and preserve the peculiarity. In a footnote to The Descent of Man, P. 423, 2nd edition, he refers to the Origin of Species in this connection. I give the passage in full:-

"I had always perceived that rare and strongly marked deviations of structure deserving to be called monstrosities could seldom be preserved through natural selection and that the preservation of even highly beneficial variations would depend to a certain extent on chance. I had also fully appreciated the *importance of mere individual differences and this led me to insist so strongly on the importance of that unconscious form of selection by man, which follows from the preservation of the most valued individuals of each breed, without any intention on his part to modify the character of the breed. But until I read an article in the North British Review which has been of more use to me than any other review, I did not see how great the chances were against the preservation of variations whether slight or strongly pronounced occurring only in single individuals."

*Perhaps this word is a misprint and should read impotence. This is suggested by the context.

From this it appears that even Darwin recognised that a profitable variation would be lost by dilution unless it occurred in a number of individuals at the same time. He insists on the importance of that


slight tendency to vary in the same way which has modified certain breeds of animals or varieties of plants, during the process of selection by man.

Now here it appears to us there is a serious flaw in the reasoning. The idea is that if the profitable variations were only very slight instead of being strongly marked they might occur in many individuals at the same time and thus be preserved. Doubtless this would be the case with variations within the limit of created capacity, but surely such variations as would be necessary to produce a totally new sense or organ are not only different in degree but also in principle. If you have a field of turnips you may find one plant very big and another very small and an almost indefinite number of graduations between the two. If then you take a medium turnip as a standard and consider all that differ from it as variations, doubtless many individuals will vary in the same way. Half or more than half of the total number may be bigger than the standard set up, and if you select the few biggest you may improve the stock, or at least keep it from deteriorating. If, however, we consider the idea of producing a totally new tendency, such as the capacity to climb and grow other turnips in the air, the case is very different. Instead of being merely a question of size or colour, varying from a medium standard, it would require variation in a totally new direction in the nature of a freak. However slight the first variation might be it would still be in the nature of a freak and would, therefore, not


be likely to occur in more than one individual at the same time. In truth the suggestion that the successive changes would be very trifling and the development very gradual, does not reduce the difficulty at all. Like the sugar coating to a pill, it only serves to make the idea rather easier to swallow. Variations, in an entirely new direction, however slight, would only be likely to occur in single individuals, and thus they would be lost by dilution.

Darwin made one strong effort to grapple with this dilution difficulty. In the Origin of Species, p. 81, he suggests that members of each variety might prefer to breed together. This clearly touches the difficulty at close quarters. If a certain family of animals which had varied in a profitable direction from the common standard of their species, held aloof from their fellows it is quite conceivable that they might retain their peculiarity. As there are many animals which do not band together to crush a common enemy, the idea that a few that had thus varied would in course of time multiply and completely supplant the old stock is intelligible. They might also be the subject of selection themselves, tending to increase their peculiar advantage, for obviously according to the law of battle those of the improved stock that were beaten and killed would generally be those that were improved the least. All this is intelligible as long as they retained the original peculiarity which gave them their advantage, and the suggestion is that the peculiarities would be retained


by the modified members preferring to breed together. It may be so. That is a point with which we are not now concerned. For the moment all we need to point out is that here again, the argument is not applicable to plants. Plants do not walk about and court each other. Flowers do not exercise any volition in the choice of a partner. They are fertilized either by the wind or insects which are intent on their own business and have no thought of the work they are incidentally performing for others. In the case of plant, then,dilution would be inevitable. Even under cultivation we are often made painfully conscious of this law and our efforts are thwarted through cross fertilization which we have been unable to prevent. The difficulty is greatly emphasised by the law of reversion which we will deal with in the next chapter, and accidental variations are readily confirmed to the old stock.

Even apart from other difficulties it appears to me that the law of dilution places a barrier in the way of Evolution on anything like the scale maintained by Darwin. I cannot conceive of the possibility of all the existing species of animals and plant having developed from a few simple types unless there was some intelligent power behind Nature. An intelligent power, not only to originate life and start the development, but also to guide its course. If mere chance variation were the only motive powers, plants and animals would remain with the faculties they originally possessed, for even if there ever appeared the


beginning of a new capacity the solitary chalice would be lost in the multitude, as a drop of milk is lost in a bucket of water.