In Pursuit of the Gene

GALTON’S DISCIPLES © 61
that no one has hitherto succeeded in drawing up general rules on the
subject.” 44
At the opening meeting of the newly named Evolution Committee,
Galton tried to interest the other members in establishing the experimental
farm. When the experimental farm seemed destined to die in committee,
Galton took it upon himself to arrange funding for Bateson’s experimental
work. Bateson’s goal, as he had explained it to Galton in his grant application,
was to cross closely related varieties that differed in particular traits
and to determine the degree to which the parental traits were blended or
remained distinct in the offspring.
In addition to arranging for further experiments on heredity, Galton
returned to work on the “law of ancestral heredity,” a rule that could be
used to predict the probability of transmission of a trait in a sibling group
based on the frequency of the appearance of the trait in previous generations.
In its first introduction in 1885, the law was applied to the continuously
varying case of human stature in an attempt to precisely quantify the
intuitively obvious idea that a person was more likely to be tall if his ancestors
were also tall. Galton’s law stated that the two parents each contributed
one-half of their deviation from the norm to the deviation of their offspring,
the four grandparents a fourth of their deviation, the eight greatgrandparents
an eighth, and the remoter ancestors in geometrically diminishing
increments. 45
When in 1896 Sir Everett Millais published The Basset Hound Club Rules
and Studbook, which contained the pedigrees of nearly a thousand hounds,
Galton was quick to see that the coat data provided the perfect opportunity
to test his ancestral law as it applied to hound coat color, either tricolor or
lemon and white, although the law would now be applied to the transmission
of a discrete rather than continuous trait. Instead of relating the contribution
of the average deviation from the norm of the various generations to
the deviation of the offspring, the law related the fraction of tricolors in
each generation to the fraction of tricolors in the sibling group. More exactly,
it stated that the average parental coat color (which is either 0 percent,
50 percent, or 100 percent tricolor, depending on whether neither,
one, or both parents, respectively, are tricolor) would determine the coat