biological fact that sexual promiscuity tends to pathological conditions
unfavorable to fecundity, that is, fertility, or the birth of offspring.
Physicians have long ago ascertained this fact, and the modern
prostitute gives illustration of it by the fact that she has few or no
children. Among the lower animal species, in which some degree of
promiscuity obtains, moreover, powerful instincts keep the sexes apart
except at the pairing season. Now, no such instincts exist in man.
Promiscuity in man would, therefore, greatly lessen the birth rate, and
any group that practiced it to any extent would soon be eliminated in
competition with other groups that did not practice it.

(6) We have finally the general social fact that promiscuity would lead
to the neglect of children. Promiscuity means that the male parent does
not remain with the female parent to care for the offspring and,
therefore, in the human species it would mean that the care of children
would be thrown wholly upon the mother. This means that the children
would have less chance of surviving. Not only would promiscuity lead to
lessening the birth rate, but it would lead to a much higher mortality
in children born. This is found to be a striking fact wherever we find
any degree of promiscuity among any people. Hence, promiscuity would
soon exterminate any people that practiced it extensively in competition
with other peoples that did not practice it.

From all of these lines of argument, without going over the evidence in
greater detail, it seems reasonable to conclude with Westermarck "that
the hypothesis of a primitive state of promiscuity has no foundation in
fact and is essentially unscientific." The facts put forth in support of
the theory do not justify the conclusion, Westermarck says, that
promiscuity has ever been a general practice among a single people and
much less that it was the primitive state. Promiscuity is found,