[Illustration: LINE OF ASCENT THAT CARRIES THE FAMILY NAME
FIG. 40.--In some pedigrees, particularly those dealing with
antiquity, the only part known is the line of ascent which carries the
family name,--what animal breeders call the tail-male. In such cases it
is evident that from the point of view of a geneticist practically
nothing is known. How insignificant any single line of ascent is, by
comparison with the whole ancestry, even for a few generations, is
graphically shown by the above chart. It is assumed in this chart that
no cousin marriages took place.]
(b) Genealogies are commonly too incomplete to be of real value.
Sometimes they deal only with the direct male line of ascent--the line
that bears the family name, or what animal breeders call the tail-male.
In this case, it is not too much to say that they are nearly devoid of
genuine value. It is customary to imagine that there is some special
virtue inherent in that line of descent which carries the family name.
Some one remarks, for instance, to Mr. Jones that he seems to be fond of
the sea.
"Yes," he replies, "You know the Joneses have been sailors for many
generations."
But the small contribution of heredity made to an individual by the line
of descent carrying his family name, in comparison with the rest of his
ancestry, may be seen from Fig.
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