Sexual Behaviors

1. Sexual Behaviors • Why do we have particular preferences? • Evolutionary Explanations • Sex differences? Psychoneuroendocrinology

2. Evolutionary explanations • Preferences/behaviors and choices…..

3. 1871 – evolution of characteristics that give organisms a reproductive advantage “Survival of the fittest” – definition of survival

4. Sexual selection based on parental investment by each sex • kin selection • certain wasp species; certain bird species • E.O. Wilson

5. thinking about parental investment and sexual selection • The sex that invests more in offspring should be more choosy or discriminating • The sex that invests less in offspring should compete more vigorously for opposite sex

6. Are there differences in the time investment in humans to produce an offspring? • amount of time for a woman – • amount of time for a man -

7. If there are differences – should the strategy for what one looks for be different?

8. If there are differences – should the strategy for what one looks for be different? males females

9. Problems with evolutionary explanations for behavior • always use posthoc observations to explain behavior • never can be really proven

10. David Buss • “The Evolution of Desire: Strategies of Human Mating” • has looked at preferences across MANY cultures from around the world with specific predictions……..

11. David Buss • Hypothesis: Men will express greater desire for, or interest in, short-term mates than women n= 148 college students; 75 men, 73 women Asked if seeking short-term mate (“ one night stand, brief affair) and independently whether they were seeking a long-term mate (defined as marrige partner) 7 point scale 1 – not at all currently seeking 7 – strongly currently seeking

12. Hypothesis • For any given period of time, men will desire a larger number of mates than will women

13. From Buss and Schmitt, 1993

14. Hypothesis • Which sex would more likely consent to sexual intercourse after knowing the other for a shorter period of time?

15. From Buss and Schmitt, 1993

16. Clark and Hatfield, 1989 • Attractive confederate approaches students on University of Hawaii campus “I have been noticing you around campus, I find you very attractive”….. • Would you go out with me tonight? • Would you come over to my apartment tonight? • Would you go to bed with me tonight?

17. Some other hypotheses • Importance of financial prospects

19. Some other hypotheses • Age of partner

21. role of hormones in sexual development and behavior • What is a hormone? • chemical substance released that binds to receptors on other cells • How is this different from a neurotransmitter?

23. Some chemicals act as both neurotransmitters AND hormones

24. role of hormones in sexual development and behavior • What is a hormone? • chemical substance released that binds to receptors on other cells • How is this different from a neurotransmitter? • travels further distance • released by glands

26. Steroid hormones • critical for aspects of sexual behavior (and development of sex organs and circuits) • ex. estrogen, testosterone, • these are lipid (fat) soluble and readily cross membranes and so can even bind to receptors in neuronal and cell nuclei

27. Steroid hormones exert effects on behaviors and/or structures in 2 ways • organizational effects • critical window for organizational effects (usually early in development)

28. Steroid hormones exert effects on behaviors and/or structures in 2 ways • organizational effects • critical window for organizational effects • effects are usually permanent • primary sexual characteristics • structural AND CNS circuitry

29. Activational Effects • activating established circuits • effects are reversible and usually occur after puberty • secondary sexual characteristics

30. So what happens to determine genotypic and phenotypic sex? • genotypic sex vs phenotypic sex • genotypic sex - determined at time of fertilization

32. 23rd chromosome is sex chromosome

33. phenotypic sex – • what you see………

34. Importance of Y chromosome: • Y chromosome controls development of gonads • gonads – sex organs that releases steroid hormones (for males; testes for females; ovaries) • on Y chromosome is a gene - HY antigen • if present- testes will develop ~ 6 weeks after conception

35. Importance of Y chromosome: • Y chromosome controls development of gonads • gonads – sex organs that releases steroid hormones (for males; testes for females; ovaries) • on Y chromosome protein is produced- HY antigen • if present testes will develop ~ 6 weeks after conception • if not present – ovaries will develop

36. Importance of Y chromosome: • Y chromosome controls development of gonads • gonads – sex organs that releases steroid hormones (for males; testes for females; ovaries) • on Y chromosome is a gene - HY antigen • if present testes will develop ~ 6 weeks after conception • if not present – ovaries will develop • up until that time a single “premordial” tissue is identical in male and females

37. What if this gene inadvertently goes onto an X chromosome? • XX male – estimated 1 in 20,000 • What if this gene is missing from a male? • XY female- estimated 1 in 20,000

38. "Nature's impulse is to create a female“ • in the absence of HY antigen (early) or male sex hormones (later in prenatal development), the organism will develop as female • male hormones (androgens like testosterone and dihydrotesterone) are necessary for undeveloped tissue to develop into male internal and external sex organs

39. So what are some things that can go wrong? • AIS – androgen insensitivity syndrome • a genetic abnormality whereby there are androgen receptors but they do not respond to androgens • females – little body hair • males – internal gonads – testes; • what after that? • 1 in 65,000 males estimated • often diagnosed at puberty

40. Congenital Adrenal Hyperplasia • estimates 1 in 13,000 to 1 in 16,000 • overactive adrenal gland releases excess androgens • diagnosed in females at birth – because of ambiguous genitalia • males not usually diagnosed at birth

41. 5 alpha reductase deficiency • 5 alpha reductase is the enzyme that produces the androgen DHT (dihydrotestosterone) • DHT is important (apparently) for the production of male external genitals

42. guave doces; Dominican Republic • first reported in 1974 • early cases – first raised as girls……… • What does it say about biology vs vs environment for determining human sex roles?

43. true hermaphroditism • intersex condition in which indvl born with ovarian and testicular tissue • can be one on one side; the other on the other or more often one or both gonads is an “ovotestis” containing both • very rare • can see XXY, XX/XY, XX XXY

44. What about organizational effects other than sex organs? • CNS – clearly affected by both organizational and activational effects of steroid hormones • Rodents have been used to gain a tremendous amount of info about the role of organizational and activational effects of steroid hormones

45. Example of experiments

47. In utero position • In species that have multiple births; developing embryos can be affected by hormones from surrounding fetuses

48. 0M, 1M and 2M females; exposed to varying levels of male hormones from developing sib nearby

49. Sexually dimorphic behaviors differences in all of these behaviors depending on whether it is a 0M or 2M female aggression male sexual behavior rough-and-tumble play sexual attractiveness onset of puberty AG distance

50. so data from numerous species that bear multiple offspring at the same time, prenatal hormones can have an influence on later structures and behavior! • What about human conditions?