The impact of genetics on animal breeding.

I F we would know how genetic knowledge is changing animal breeding practices or is likely soon to change them, we can probably get our best clues by asking what the animal breeders are studying now. Predictions made on this basis will not be wholly accurate, of course. The "endless frontier" nature of science precludes high accuracy in any method of predicting the future, especially the distant future. Yet always there is some time-lag in applying newly won knowledge to the arts and business of production. Predictions of the immediate future on the basis of that time-lag are likely to be a bit better than guesses. Genuinely new knowledge and developments are more likely to be found where several investigators are delving, more or less independently, in a field than by lucky chance or sudden inspiration descending on a stray worker who is thinking of something else. To be sure, the latter does happen, even if but rarely, and its consequences are sometimes tremendously important. Saul was out looking for his father's asses when he found a kingdom! Predicting the future by studying current research is a bit like watching a river at a given point and predicting its downstream course. Usually we can see a few hundred yards with practical certainty. Often by looking at the hills on the horizon we can make a fair estimate of its general course for several miles. But we are almost certain to be wrong if we predict that it will continue indefinitely in that direction for hundreds of miles. The first half century of genetics, dating that from the rediscovery of Mendel's laws, is described in a forthcoming book 2 which includes many details about the impact genetics has already had on animal breeding, as well as on plant breeding and on man's ideas about biology and about himself. I t would be wasteful to repeat those here in detail, but a few will provide background for what follows. In genetics itself, the first twenty years were devoted largely to testing whether Mendel's laws were true, whether they applied to all characters or only to certain kinds such as colors and superficial details of form,