idea that reconciles and adjudicates
among my warring motives. In it I find both concentration of myself and
escape from myself; in a word, I find Salvation.

2.9. INDIVIDUALITY AN INTERLUDE.

I would like in a parenthetical section to expand and render rather more
concrete this idea of the species as one divaricating flow of blood,
by an appeal to its arithmetical aspect. I do not know if it has ever
occurred to the reader to compute the number of his living ancestors at
some definite date, at, let us say, the year one of the Christian era.
Everyone has two parents and four grandparents, most people have eight
great-grandparents, and if we ignore the possibility of intermarriage we
shall go on to a fresh power of two with every generation, thus:--

Column 1: Number of generations.

Column 2: Number of ancestors.

3: 8
4: 16
5: 32
7: 128
10: 1,024
20: 126,976
30: 15,745,024
40: 1,956,282,976

I do not know whether the average age of the parent at the birth of a
child under modern conditions can be determined from existing figures.
There is, I should think, a strong presumption that it has been a rising
age. There may have been a time in the past when most women were mothers
in their early teens and bore most or all of their children before
thirty, and when men had done the greater part of their procreation
before thirty-five; this is still the case in many tropical climates,
and I do not think I favour my case unduly by assuming that the average
parent must be about, or even less than, five and twenty. This
gives four generations to a century. At that rate and DISREGARDING
INTERMARRIAGE OF RELATIONS the ancestors living a thousand years ago
needed to account for a living person would be double the estimated
population of the world. But it is obvious that if a person sprang from
a marriage of first cousins, the eight ancestors of the third generation
are cut down to six; if of cousins at the next stage, to fourteen in the
fourth. And every time that a common pair of ancestors appears in any
generation, the number of ancestors in that generation must be reduced
by two from our original figures, or if it is only one common ancestor,
by one, and as we go back that reduction will have to be doubled,
quadrupled and so on. I daresay that by the time anyone gets to the 8916
names of his Elizabethan ancestors he w