SPECULATIONS ON THE ORIGINS OF HUMAN SEXUAL BEHAVIOR

SPECULATIONS ON THE ORIGINS OF HUMAN SEXUAL BEHAVIOR Leanna Wolfe, Ph. D. Institute for Advanced Study of Human Sexuality February 9, 2011

When the gods gave people sex, they gave us a wonderful thing. Sex is food: just as people cannot survive without eating, hunger for sex can cause people to die Nisa The Story of Kung Woman

What’s Unique About Humans? �Hidden Ovulation �Extended Childhoods �Human Infants are the least mature apes at birth �Year Round Female Receptivity �Irrelevant of ovulation �Bonding �Serial Pair bonding �Polygamy/Monogamy � Based on economic, social and cultural factors

Just So Stories… �Adam and Eve �Mitochondrial Eve �Early Emergence of Male Provisioning Female and her Infants �Owen Lovejoy �Hidden Ovulation emerged to enable Pair Bonding �Helen Fisher

Mitochondrial Eve Newsweek’s most popular cover ever The discovery of a relatively recent emergence of Homo sapiens (less than 200, 000 years ago) was lost at the thought of there having been a Real Eve…

Extended Childhoods • Babies Less Mature at Birth • Mothers Require more Provisioning • Cultural Learning Important for Survival Dikika Child 3. 3 mya Advent of the Nuclear Family? ? ?

Human-Ape Origins

Distribution of Apes

The Sex Contract Owen Lovejoy, Male Paleoanthropologist Immature young caused females and males to form long term pair bonds in order to facilitate care for the young A Maasai Tribe Shares Meat Ethnographic data from foraging societies establishes that a woman’s offspring will be well-fed simply if she is part of a tribe in which there is at least one good hunter.

A Sex for Meat Exchange? �Certainly, but no evidence that it took the form of monogamous pair bonds �Successful male hunters might have exchanged their bounties with multiple females, ultimately accessing sexual variety �Females in the quest for as much meat as possible might have gladly exchanged sex with multiple male hunters

Bonobo Estrus Displays Bonobo Estrus Display Attracts Attention! Bonobo Full Estrus Display

Human Ovulation Displays… Ovulation Test Kit Measures rise of Luteinizing Hormone, signally impending ovulation Female Showing Lots of Skin (possibly ovulating)

Explanations for Hidden Ovulation Helen Fisher Anthropologist ØMate Guarding ØPairbonding ØLove Sarah Blaffer Hrdy Anthropologist ØConfuse Males ØPrevent Infanticide ØFemale Independence

Sexual Dimorphism As an Indicator of Polygyny Differences in size between male and female were more pronounced amongst the Australopithecine than modern day humans.

Testicle Size As an Indicator of Non-monogamy With their relatively large testicles male chimpanzees are wellequipped for intrauterine sperm wars Humans also have relatively large testicles…

Y-Chromosome Distribution • Less diversity than Xchromosomes • Reveals widespread long-lasting polygyny among human populations

Sperm Competition �An indicator of polyandrous mating patterns Biologists Robin Baker and Mark Bellis observed that females that engaged in extra-pair copulations retained more of their lover’s ejaculate (70%) following orgasm than their spouse/home partner’s (40%). Thus sperm competition could easily foster high levels of genetic diversity.

Sperm Competition �Three unique kinds of sperm (blocker, fighter and egg penetrator) were distributed differently depending on the context of lovemaking. Sperm from different males might compete Only Egg Penetrator Sperm could cause a pregnancy

Reproductive Strategies �Male (re: MPI) �Cad (low investment) �Lad/Pair Bonded Mate (high investment) �Female (discerning Mate Value) �Monogamous Mate �Sexy Son Hypothesis �Partible Paternity �Extended Family/Tribe/Village/Community

Sexy Son Hypothesis David Buss, Evolutionary Psychologist Females seek testosteronated hunks near ovulation while long term bonding is sought with fatherly resource providers.

Humans are by Nature Hypersexual and Promiscuous S. E. Ex – Socio Erotic Exchange Christopher Ryan Research Psychologist Primeval societies engaged in communal parenting, group sex and were oblivious to paternity

How Males Care About Paternity �Dogon Menstrual Huts �Contemporary DNA Testing �Chastity Belts �Female Genital Mutilations (FGM) �Post Nuptial Virginity Tests

Why Males Care… § Fear of Being Cuckolded into Investing in Someone Else’s Genes § Assured that Just Their Genes Go Into the Future § Pass on Wealth/Resources/Legacy to Heirs When Males Don’t Care § When They Are Bonobos § When the State/Community/Village is Responsible for Resources § Exchanging Service/Resources for Sexual Access

Is Chimp Social Sexuality Natural? • Visible Estrus • Multi-Male Multi-Female Troops • Social Sexual Hierarchies • Mother-Infant Bonds

Is Bonobo Social Sexuality Natural? • Females Rule the Business o. Paternity Irrelevant • Homosexuality o GG Rubbing o Penis Fencing • Pedophilia • Disputes Resolved with Sex • Group Sexual Bonding

Serial Monogamy: Is it Natural? �Lust �testosterone �Attraction �Dopamine �Norepinephrine �Attachment �Oxytocin �Vasopressin �Detachment

Is Partible Paternity Natural? • Multiple Fathers • Cooperative Parenting • Group Sex Rituals • Communal Resources Ache (Amazon) Children Sharing Food Ache Children with one of their Fathers • Fetal Growth Requires Regular Inseminations • Multiple Fathers’ Characteristics Inherited

Is it All in the Eye of the Beholder?