Lynn Saxon

If Darwinian natural selection is to be mocked with regard to humans then we should at least start with some understanding of it as it does apply to other species.

In sexual selection genes spread when an individual out-reproduces others of the same sex. Two different naturally selected outcomes – the two sexes – then result within the same species.

Darwin argued for a female role in evolution through active female mate choice. A passive female role, though, is a potential outcome of Ryan and Jethá’s argument for casual female promiscuity.

The sex which invests most in parenting any offspring is a limited reproductive resource competed for by the sex which invests the least.

Natural selection is a consequence of differential reproductive success.

Ryan and Jethá distort Darwin’s response to the ideas about group marriage, and they fail to explain the impact of the misinterpretation of classificatory kinship terms on Morgan’s ideas.

Ryan and Jethá, and Morgan, miss the movement of sexually mature individuals between groups; they erroneously imagine the group to be a bounded entity through time with members living together and mating together for life.

The natural world, along with its wonder and beauty, contains considerable natural pain. Individuals both suffer and inflict suffering doing what their genes ‘want’ them to do, including – or especially – with regard to sex and reproduction.

Everything about the two sexes follows from anisogamy.This is a critical point - fundamentally the evolutionary movement from asexual to sexual reproduction ie fusion of dissimilar gametes.]

Many examples of mating behaviours show that ‘natural’ sexual behaviours are not necessarily ‘enjoyed’ by the two sexes. There can often be sexual conflict over if, when, or how often to mate. [And it is not always the females who are investing energy in parenting - consider the reproduction strategies of seahorses - the female produces eggs which are held, fertilised and nourished in the sac of the male (with placenta-like processes) before the male undergoes contractions and gives birth.]

When Ryan and Jethá question whether there can be “a discrete genetic basis for something as amorphous as preoccupation with paternity” they would do well to remember infanticide by males and other male reproductive strategies shaped by a naturally selected and completely unconscious genetic “preoccupation with paternity”.

The exchange of sex for resources – direct benefits – is common across species, making ‘whoredom’ a beneficial reproductive strategy for females of most species.

The distinction between receptive and proceptive female sexual behaviour is an important one, distinguishing between a passive acceptance and a more active solicitation of sex.

Females of a number of species have evolved ‘fake’ proceptive sexual behaviours to feign fertility, confuse paternity, and thereby reduce the costs of infanticide by males.

Ryan and Jethá give no consideration to our common ancestor with the gorilla or to evolution along the different ape lineages over millions of years; they only have a single human ancestor model: the modern bonobo.

Though monogamy is not found in primate social groups, polygyny is. Ryan and Jethá [mid]present Rousseau ...[who] clearly feared that unleashing the female libido would lead to the collapse of society.

Ryan and Jethá distort Anne Pusey’s work to use as ‘evidence’ for general chimpanzee female promiscuity across community boundaries, and relaxed, possibly even friendly, relations between communities.

Genetic evidence supports the evolution of bonobos from a small founder population that became separated from other chimpanzees....[and] supports selection acting strongly in the chimpanzee lineage in connection to promiscuous mating after the Pan/Homo divergence. Ryan and Jethá use a vasopressin receptor gene to falsely create a “crucial” oxytocin link between humans and bonobos;...[it exists] in gorillas and Central African chimpanzees as well as humans and bonobos.

The clear distinction between sex and “sex” in bonobos is not made by the authors and a false sense of adult human-like sexual behaviour is presented. Bonobo sex is very much in the context of food and femalebonobos turn out to be strategic ‘whores’.