The author then launches into a discussion of human intelligence, the most important feature of human evolution, and how it cannot be fully explained by mutational selection. Modern humans are smarter than what is demanded by our evolutionary experience as hunter-gatherers. The difficulty lies in the inability of natural selection to answer the following question: how can a complex set of genes, controlling expensive traits with little immediate benefit, come into permanent existence within a short time period in every member of a small population (which was dispersed and geographically isolated over a huge planet) which had a low reproductive output and a low mutation rate?
The book concludes with a speculative epigenetic theory of intelligence that does not require DNA mutations as a source of evolution. Although the book is comprehensible by anyone with a college education, this last section in particular should intrigue both layman and expert alike.
Contents: Evolution: Darwin and Natural Selection; Darwin Analyzed; Lamarck; The Thin Bone Vault: Definition of Intelligence; A Brief History of the Mind; Population; Culture; Animal Intelligence; Evolutionary Potential: Elementary Genetics; Gene Variability, Examples; Directed Mutations; Genetics and Intelligence; Evolution of Intelligence, an Epigenetic Model: Epigenetics; The Cranial Feedback Mechanism.