Natural selection deals ruthlessly with any population, bird or beaver, which fails to solve the problems of its environment with all those resources, learned or unlearned, which may be at its disposal.

What could not be denied was that in vast segments of the animal world natural selection of the most qualified individuals took place not by competition for females but by competition for space.

Men, unlike mockingbirds, have the capacity for systematic self-delusion. We echo each other with equal precision, equal eloquence, equal assurance.

Human war has been the most successful of our cultural traditions.

Aggressiveness is the principal guarantor of survival.

For the soundest of evolutionary reasons man appears at his best when times are worst.

Animal language is a contagious expression of mood effecting communication between social partners.