redity is the
interpretation of genealogy, and eugenics the application of heredity.
Genealogy should give its students a vision of the species as a great
group of ever-changing, interrelated organisms, a great network
originating in the obscurity of the past, stretching forward into the
obscurity of the future, every individual in it organically related to
every other, and all of them the heritors of the past in a very real
sense.

Genealogists do well in giving a realization of the importance of the
family, but they err if they base this teaching altogether on the
family's pride in some remote ancestor who, even though he bore the
family name and was a prodigy of virtues, probably counts for very
little in the individual's make-up to-day. To take a concrete though
wholly imaginary illustration: what man would not feel a certain
satisfaction in being a lineal descendant of George Washington? And yet,
if the Father of his Country be placed at only four removes from the
living individual, nothing is more certain than that this hypothetical
living individual had fifteen other ancestors in George Washington's
generation, any one of whom may play as great or a greater part in his
ancestry; and so remote are they all that, as a statistical average, it
is calculated that the contribution of George Washington to the ancestry
of the hypothetical living individual would be perhaps not more than
one-third of 1% of the total. The small influence of one of these remote
ancestors may be seen at a glance, if a chart of all the ancestors up to
the generation of the great hero is made. Following out the
illustration, a pedigree based on George Washington would look like the
diagram in Fig. 41. In more remote generations, the probable biological
influence of the ancestor becomes practically nil. Thus Americans who
trace their descent to some royal personage of England or the Continent,
a dozen generations ago, may get a certain amount of spiritual
satisfaction out of the relationship, but they certainly can derive
little real help, of a hereditary kind, from this ancestor. And when
one goes farther back,--as to William the Conqueror, who seems to rank
with the Mayflower immigrants as a progenitor of many descendants--the
claim of descent becomes really a joke. If 24 generations have elapsed
between the present and the time of William the Conqueror, every
individual living to-day must have had living in the epoch of the Norman
conquest