Organization are economic provision and biological maintenance; a stream of children is as vital as a continuity of food.
It is highly improbable that the first human beings lived in isolated families, even in the hunting stage; for the inferiority of man in physiological organs of defense would have left such families a prey to marauding beasts.
Among the lower animals there is no care of progeny; consequently eggs are spawned in great number, and some survive and develop while the great majority are eaten or destroyed.