THE INHERITANCE OF PRODUCTIVITY IN FARM LIVE STOCK.
281
There can be no doubt of the value of simple selection, combined with
pedigree and the progeny test as a definite means for improving the productivity
of our dairy cattle. There is equally no doubt that the rate of improvement is
somewhat slower than it was. Granted time, patience, and money, can we
reasonably expect that selection alone will effect the desired improvement in
a manner such as Winter has shown to be possible with maize ?
I do not think so. Without more fundamental knowledge, the rate of im-
provement is bound to get slower. The problem is not the simple one of selection
for one particular object. In striving to achieve a definite race of high producers,
we desire to obtain a multitude of characters each of which depends upon a multi-
tude of genes. I do not suggest that it is worth our while to determine precisely
the number of genes involved in, say, an increase in the sugar-content of milk.
But what is definitely of value is to discover whether an increase in the sugar-
content can be secured by simple selection, and whether it is genetically or
physiologically incompatible with the selection of other important characteristics.
Unless we know these things, selection is bound to bring in its train a considerable
amount of disappointment.
But have we as yet obtained an adequate knowledge of the pure science of
genetics ? He would be a fool who would so presume. Take, for instance,
Dr. Fisher's theory of the evolution of dominance : with Nature as the agent of
selection it is essential that those characters which benefit the organism be trans-
mitted in a dominant manner. Dominance is, therefore, acquired by such charac¬
ters, though we are ignorant of the means by which it is acquired. With man
as the selecting agent, it is of decided benefit to the species that the desired
characters (i.e., the productive characters of our live stock) be transmitted in a
recessive manner. At present they most decidedly are not. Is it possible that
just outside our sphere of knowledge there exists a mechanism for the evolution
of recessivity ?
But such an hypothesis as the evolution of recessivity demands systematized
inbreeding for productivity. The outcome of the recently published work of
twenty years' inbreeding by the United States Bureau of Dairy Industry [2]
shows great possibilities in the direction of stabilizing a high yield (1,700 gallons)
by this method. Success in inbreeding demands, however, a certain knowledge
of the mode of inheritance of the character and particularly if sex-linkage is operat-
ing. Here is a further reason for research both pure and applied.
The demands of the market are not stable. The consumer of agricultural
produce is—to the producer at any rate—fickle in his likes and dislikes.
Supposing selection to be more effective than I am willing to admit, it is bound
to take at least twenty years to obtain the desired type. In the meantime the
taste of the consumer is sure to have changed. Not only is the taste of
the consumer liable to alter in twenty years, but the general methods of
production are also likely to be revolutionized by circumstances over which the