I read this book a second time recently.
I appreciate that such a scholarly and well-researched text was written by an amateur scientist. It was written as a critique of a more popular book with a similar title. This other book attempted to make a case that humans in the pre-agricultural era (i.e. over 10 000 years ago) had a much more promiscuous lifestyle, which for them was supposedly healthier and more peaceful--then with the implication that we should try to emulate this in modern society.
Saxon's book looks at almost every claim made by the other authors, and shows how their analysis was biased, incomplete, or just completely wrong, in terms of historical and anthropological data, as well as genetics and evolutionary biology. Saxon shows that the authors of the other book particularly do not address the very dark side of almost every case study described. The areas of focus in both books include social and sexual behaviour in primate species most closely related to humans (chimpanzees, bonobos, and gorillas), as well as cultures of remote present-day groups, such as those living in the Amazon. A particular emphasis is the genetic basis (through natural selection) of behavioural traits.
The subject of the genetic foundations of animal behaviour, and of the mechanism of evolution through natural selection, should be part of everyone's common knowledge. Books by naturalists, biologists, or geneticists on this subject are not only informative from a scientific point of view, but are fascinating in the same way that watching a good nature documentary would be: most of us are unaware of the life cycles and behavioural patterns of most of the species with whom we share the earth. The stories, often about species that many of us have never heard of, but also sometimes about familiar species, are almost always interesting, but sometimes shocking or disturbing or intensely dramatic. The best science writer in this genre is Richard Dawkins -- whether or not you like his philosophical point of view, it is essential and often entertaining reading to learn about other species, with the eye of a great naturalist.
Saxon shows that we cannot escape some of the problems which exist in relationship and sexual dynamics in humans, including jealousy. There is a strong genetic foundation for pair bonding in our species, though not without tensions, jealousies, and strong desires, which differ between the sexes, to have other relationships outside of the pair bond; but such excursions outside of a pair bond cannot occur without a substantial cost, often manifest in behaviour which is in part genetically determined.
None of these genetic factors justifies a social policy which constrains relationship choices... social and relationship freedoms, as well as guaranteed personal rights, are aspects of social justice that have thankfully grown in our country in the past century; they must be created and legislated, whether or not they have always been favoured in our species through genetic/natural selective forces in the distant past.