Polyamory in Paleo Pride

G.F.Miller: "evolutionary innovations seems focused on the details of penis shape

body-size dimorphism: the average difference in size between adult males and females in a given species. among apes for example, male gorillas and orangutans average about twice the size of females, while male chimps, bonobos and humans are from 10 to 20 percent bigger and heavier than the females. male and female gibbons are of equal stature. among mammals generally and particularly among primates, body-size dimorphism is correlated with male competion over mating (Lawler 2000).
the biggest, baddest gorillas will pass genes for for bigness, badness into the next generation.
on the other hand, in species with little struggle over females, there is less biologicale imperatvie for the males to evolve larger, stronger body, so they normally don't. that's why the sexually monogamous gibbons are virtually identical in size.
looking at our modest body-size dimorphism, it's a good bet that males haven't been fighting much over females in the past few million years.
without access to the skeletal data on body-size dimorphism we have today, Darwin speculated that early humans may have lived in a harem-based system.
the culturale conditions necessary for some males to accumulate sufficient political power and wealth to support multiple wives and their children simply did not exist before agriculture.

note the assumption shared by both these interpretations: female sexual retiscence. in both scenarios , female "honor" is intact. in the second interpretation, only the male's natural fidelity is in doubt.

Winge coined the word sperm competition; G.Parker later defined the concept. if the sperm of more than one male are present in the reproductive tract of an ovulating female, the spermatozoa them-selves compete to fertilize the ovum. females of species that engage in sperm competition typically have various tricks to advertize thei fertility, thereby inviting more competitors. their provocations range from sexy vocalizations or scents to genital swelling that turn every shade of lipstick red from Berry Sexy to Rouge Soleil.


male apes living in multiple social groups (such as chimps, bonobos and humans) have larger testes, housed in an external scrotum, mature later than females, and prduce large volumes of ejaculate containing greater concentrations of sperm cells than primates in which females normally mate with only one male per cycle (such as gorillas, gibbons and orangutans).

even if Darwin suspected something like sperm competition had palyed a role in human evolution, he could hardly be expectes to drag the angelic Victorian woman down from her pedestal.

J.Diamond (1991) considers the theory of testis size to be "one of the triumphs of modern physical anthropology" .like most great ideas, the theory of testis size is simple: species that copulate more often need larger testes, and species in which several males routinely copulate with one ovulating female need even bigger testes.

through generations, male gorillas eveolved impressive muscles for their reproductive struggle, while their relatively unimportant genitals dwindled down to the bare minimuum needed for uncontested fertilization. conversely, male chimps, bonobos and humans had less need for oversized muscles for fighting but eveolved larger, more powerful testicles and, in case of humans, a much more interesting penis.

himans fall in the middle ground between gorillas and bonobos on the tesicular volume/body-mass scale. those who argue that our species has been sexually monogamous for millions of year point out that human testicles are smaller than those of chimps and bonobos. those who challenge standard narrative (like us, for example) note that human testicular ratios are far beyond of the polygynous gorilla or the monogamous gibbon.
so, is the human scrotus half-empty or half-full?

a one-man/one-woman system reduces competion among males, as the pool of available females isn't being dominated by just few men, leaving more women available for less desired men. but a mating system in which both males and females tipically have multiple sexual relationships running in parallel reduce male mating competion just as effecively, if not more so. and given that both of the species closest to us practice multimale-multifemale mating, this seems by far the more likely scenario.

humans, chimps, and bonobos -but not gorillas- show "accelerated evolution of genes involved in sperm and seminal fluid production" associated with "multiple insemination".

Margulis and Sagan: men's "souped-up genitals" backed by "a lot of spermatic firepower" would be worthwhile only if there were "some sorts of race or contest. otherwise," they write "they seem to be excessive" (1991)

Souped-up genitals. Spermatic firepower. now we are talking!
indication of spermatic firepower are evident in the differences between a man's first sprout and his last.
the first sprout contain chemical that protect against various kind of chemical attack. what sort of chemical attack? aside from leucocytes and antigens present in a woman's reproductive tract (more on that later) , they protect the sperm from the chemical in the latter spurts of other men's ejaculate. these final spurts contain a spermicidal substance that slows the advance of any latecomers. in other words, competing sperm from other men seems to be anticipated in the chemistry of men's semen, both in the early spruts (protective) and in the later spurts (attacking). (Lindholmer 1973)

consider the story of Heracles and Iphicles: the night preceeding Amphitryon's marriage to Alcmene, Zeus disguised himself as Amphitrion and slept with the bride-to-be. the following night, Amphitrion consummated her marriage. Alcmene had twins: Iphycles (fathered by Amphitrion) and Eracles (fathered by Zeus). clearly, the ancient Greeks had an inkling of sperm competition.

a man's sperm production increases significantly when he has not seen his partner for a few days, regardless of whetever or not he ejaculated during her absence. this finding conforms to the notion that sperm competition has played a role in human evolution and may even reflect an adaptation to monogamy.

women have reported that their partners tend to be more vigorous in bed after a separation or if infidelity is suspected.
sacrosant female sexuality it's a vision that Darwin cultivated in public.

flared glans of the human pensis forming the coronal ridge, combined with the repeated thrusting action characteristic of human intercourse creates a vacuum in the female's reproductive tract. this vacum pulls any previously deposited semen away from the ovum, thus aiding the sperm about to be sent into action. but wouldn't this vacuum action also draw away a man's own sperm? no, because upon ejaculation, the head of the penis shrinks in size before any loss of tumescence (stifness) in the shaft, thus neutralizing the suction that might have pulled his own boys back. very clever.

"We theorize that as a consequence of competition for paternity, human males evolved uniquely configured penises that function to displace semen from the female vagina left by other males.

without sperm warfare during human evolution, men would have tiny genitals and produce few sperm. ... there would be no thrusting during intercourse, no sex dreams or fantasies, no masturbation, and we would each feel like having intercourse only a dozen or so times in our entire lives.

FVC female copulatory vocalization SEE:
Stuart Semple 2001: vocalization are particularly common among the primates and evidence is now accumulating that by calling a female incites males in her group

although Dixon classifies humans as mildly polygynous , he writes: "one might argue that..the female's orgasm is rewarding, increases her willngness to copulate with a variety of males rather than one partner, and thus promotes sperm competition.".

the female reproductive system is capable of making subtle judgements based upon the chemical signature of different men's sperm cells. these assesments may go well beyond general wealth to the subtetlies of immunological compatibility. the genetic compatibility of different men with a given woman means that sperm quality is a relative characteristic. thus, as Anne Pusey (2001) explains: "females may benefit from sampling many maes, and different females will not necessarily benefit from mating with the same "high quality" male".
(...) a woman (and ultimately, her child) may benefit by sampling many males and letting her body decide whose sperm fertilizes her.

anatomical and physiological obstacles are in the vagina, cervis, and on the surface of the ovum. ***the complexity of the human cervix suggests it evolved to filter the sperm of various males.

if it is true that multiple mating was common in human evolution, the apparent mismatch between the relatively quick male orgasmic response and the so-called delayed female response makes sense. the male's quick orgasm lessens the chances of being interrupted by predators or other males, while the female and her child would benefit by exercising some preconscious control over which spermatozoa would be the most likely to fertilize her ovum.