"Atavism," or "breeding back," or "reversion," may reach back through
thousands of generations, and some trait of the cave-man, or the beast,
may reappear in a child of Twentieth Century civilisation.
Darwin, in _The Descent of Man_, Chapter II, gives many instances
of "atavism," or breeding back, by human beings to apish and even
quadrupedal characteristics. Alluding to a case cited by Mr. J. Wood, in
which a man had seven muscles "proper to certain apes," Darwin says:
It is quite incredible that a man should through mere accident
abnormally resemble certain apes in no less than seven of his muscles,
if there had been no genetic connection between them. On the other hand,
if man is descended from some apelike creature, no valid reason can
be assigned why certain muscles should not suddenly reappear after
an interval of many thousand generations, in the same manner as with
horses, asses, and mules, dark-coloured stripes suddenly reappear on the
legs and shoulders after an interval of hundreds, or, more probably, of
thousands of generations.
Dr. Lydston, in The Diseases of Society (Lippincott: 1904) says:
The outcropping of ancestral types of mentality is observed to underlie
many of the manifestations of vice and crime. These ancestral types
or traits may revert farther back even than the savage progenitors of
civilised man, and approximate those of the lower animals who, in their
turn, stand behind the savage in the line of descent.
This "reversion to older and lower types," or "breeding back," is
important, because it is the source of much crime--the origin of very
many "Bottom Dogs," as we shall see. But at present we need only notice
that heredity, or breed, reaches back through immense distances of time;
so that a man inherits not only from savage ancestors, but also from
the brutes. And man has no power to _choose_ his breed, has no choice of
ancestors, but must take the qualities of body and mind they hand down
to him, be those qualities good or bad.
Descent, or breed, does not work regularly. Any trait of any ancestor,
beast or man, near or remote, may crop up suddenly in any new
generation. A child may bear little likeness to its father or mother: it
may be more like its great-grandfather, its uncle, or its aunt.
It is as though every dead fore-parent back to the dimmest horizon of
time, were liable to put a ghostly finger in the pie, to mend or mar it.
Let us now use a simple illustration of the workings of heredity,
variation, and atavism, or breeding back.
There is no need to trouble ourselves with the scientific explanations.
What we have to understand is that children inherit qualities from their
ancestors; that children vary from their ancestors and from each
other; and that old types or old qualities may crop out suddenly and
unexpectedly in a new generation. Knowing, as we do, that children
inherit from their parents and fore-parents, the rest may be made, quite
plain without a single scientific word.
In our illustration we will take for parents and children bottles, and
for hereditary qualities beads of different colours.