Through an infinite slaughter of the least fit, such groups arrive at
some kind of instinctive adjustment to produce and protect the young.
The crudest human intelligence must have eliminated much of the waste
involved, by comprehending obvious cause-and-effect relations which
animals have to arrive at through trial and error methods.

For example, an intelligence capable of employing artificial weapons is
also able to see that the wielder of these for group defence cannot be
encumbered with baggage or children when the group is in movement. Hence
women became the burden bearers, and took care of the children, even
after the nursing period. War parties could not generally be mixed, for
the obvious reasons that such women as did not have young children would
be pregnant a good deal of the time, or likely to become so. Moreover, a
hunter and fighter must not have his courage, ferocity and physical
initiative undermined by unsuitable employments and associations.

In a semi-settled group, the hunter and warrior cannot be relied upon to
keep hearth-fires burning or tend crops, even though he may occasionally
have time for such activities. These duties are therefore relegated to
the women, whose child-bearing functions impose upon them a more
sedentary existence. Women must reproduce practically up to their full
capacity to fill up the gaps made by war, accident and disease as well
as death from old age. To this biological service which they alone can
perform are added those which lie nearest it and interfere least with
carrying it out.

We must therefore keep in view _all_ the activities of any group in
which the sex problem is being studied. There is a certain tendency to
disregard the female specialization to child-bearing, and to regard the