In Pursuit of the Gene

298 ¨ NOTES TO PAGES 36–42
35. Letter from Galton to George Howard Darwin, May 17, 1876, in Ruth
Schwartz Cowan, “Francis Galton’s Statistical Ideas: The Influence of Eugenics,”
Isis, 63 (1972): 518.
36. Letter from Galton to George Darwin, Jan. 5, 1877, in Pearson, Galton, 3B:465.
37. Galton introduced a clever extension of the normal theory that required a revamped
quincunx to illustrate. See Stigler, History of Statistics, 275–281, for a detailed
explanation of the theory.
38. Cowan, “Galton’s Statistical Idea,” 521 n. 44.
39. Galton, “Opening Address,” 507.
40. For example, the “1” in the upper right corner of the graph indicates that
there was 1 adult child in the range between 4 and 5 inches above average height
born to mid-parents who were between 3 and 4 inches above average.
41. Francis Galton, Memories of My Life (London: Methuen and Co., 1908), 302.
42. Letter from Galton to Tertius, Nov. 3, 1840, in Pearson, Galton, 1:144
43. Pearson, Galton, 1:302–303.
44. Francis Galton, “Regression toward Mediocrity in Stature,” Miscellanea of the
Journal of the Anthropological Institute of Great Britain 15 (1886): 255; and again in Galton,
Natural Inheritance, 102
45. Galton, “Opening Address,” 507
46. Galton, “Regression toward Mediocrity,” 253
47. Ibid., 256.
48. Ibid, 253.
49. Galton’s error had been to group together in each height class a variety of
people from different ancestries. Under this procedure, a significant number of exceptionally
tall (or short) people who came from families of unexceptional height
and whose exceptional height was due to nutrition or other environmental factors
that were not heritable were grouped together with people who carried tall genes.
It was simply not true that exceptional parent types would necessarily have less exceptional
children, or that the plants with large seeds would give rise to plants with
seeds of smaller size. Contrary to Galton’s belief, the offspring of a marriage of tall
families would, on average, be as tall as their parents, and likewise, large seeds derived
from a single ancestral line would have given rise to progeny peas that were,
on average, as large as their parental seeds. Furthermore, if tall men and women
were selected out over a period of generations (until they were homozygous for
the genes coding for increased height), there would ultimately be no regression at
all in height. Theoretically, selective breeding can create a race of giants.