Sexual Reproduction and Monogamy

1. Sexual Reproduction and Monogamy from “The Myth of Monogamy” by Barash and Lipton (2001)

2. CB 13.5 Evolution: A species’ genetic component changes as the individuals reproduce. These changes are based on how the DNA changes and who reproduces.

3. haploid X 23 in humans X 23 in humans diploid X 23 in humans Sexual Reproduction = The combination of genes inherited from Mom and Dad.

4. Asexual Reproduction Sexual Reproduction vs. extremely low genetic diversity greater genetic diversity

5. Asexual Reproduction genetically identical to parent (this tree can reproduce both sexually and asexually)

6. Cons: Need two individuals Hard to find mate Diseases/Competition Pros: Genetic diversity Why does sexual reproduction exist?

7. Screw worm flies

8. F M sterile Sterile male screw worm flies led to decreased populations because of screw worm monogamy.

9. F M sterile In most other species, because females mate with multiple males, introduction of sterile males has little effect. Sterile male screw worm flies led to decreased populations because of screw worm monogamy. F M sterile

10. In most other species, because females mate with multiple males, introduction of sterile males has little effect. Hi, want to study biology together? F M F M fertile sterile

11. 10-40% of offspring in “monogamous” bird species are fathered by an extra-pair male

12. Social Monogamy = pair lives/works together, but not “faithful” • Sexual Monogamy = pair raise young and only copulate with each other

13. In mammals, child-rearing is most commonly done by the female. She provides milk.

14. Less than 0.01% of mammals are monogamous

15. Do Males and Females have different attitudes toward sex and relationships?

16. Male answers: …Would you go out with me tonight? = 50% yes Female answers: …Would you go out with me tonight? = 50% yes On a college campus an attractive male or female asked the opposite sex: “I have been noticing you around campus. I find you very attractive…”

17. Male answers: …Would you go out with me tonight? = 50% yes …Would you come to my apartment tonight? = 69% yes Female answers: …Would you go out with me tonight? = 50% yes …Would you come to my apartment tonight? = 6% yes On a college campus an attractive male or female asked the opposite sex: “I have been noticing you around campus. I find you very attractive…”

18. Male answers: …Would you go out with me tonight? = 50% yes …Would you come to my apartment tonight? = 69% yes …Would you go to bed with me tonight? = 75% yes Female answers: …Would you go out with me tonight? = 50% yes …Would you come to my apartment tonight? = 6% yes …Would you go to bed with me tonight? = 0% yes On a college campus an attractive male or female asked the opposite sex: “I have been noticing you around campus. I find you very attractive…”

19. Why do Males and Females have different attitudes toward sex and relationships?

20. The male perspective on monogamy

21. Eggs require large resource input. A clutch of bird eggs can be ~20% of bird’s weight. Sperm are cheap.

22. Human Males: 250,000,000 sperm/ ejaculation Human Females: ~1 egg/month

23. CB 46.15 The female reproductive system CB 46.15

24. Sperm competition: Sperm can survive for several days in a woman’s reproductive tract. In Great Britain in a survey of 4,000 women… 0.5% had sex with 2 different men within 30 minutes… 30% within 24 hours = sperm competition.

25. CB 46.15 The female reproductive system CB 46.15

26. Female mammals provide additional resources in form of milk.

27. Mating pairs share genetic information and possibly help in child-rearing

28. What are the consequences of the different male and female attitudes toward sex and relationships?

29. Zebra Finch

30. Zebra finch pairs were allowed to mate ~9 times

31. Then a new male was brought in and allowed to mate with the female once.

32. Last male advantage Original male (mated 9 times) fathered 46% of offspring The last male that only mated once fathered 54% of offspring

33. Last male advantage To ensure fatherhood males mate guard and produce copious quantities of sperm

34. After successfully mating, male purple martins call and attract younger males Purple Martins

35. The older males then cuckold the younger male’s females Younger males with nests near older males only father 29% of eggs in their nests.

36. Older males produce 4.1 offspring with their mate and 3.6 by younger neighbor’s mate. Younger males with nests near older males only father 29% of eggs in their nests.

37. Older males produce 4.1 offspring with their mate and 3.6 by younger neighbor’s mate. What advantage is their for females to accept or solicit EPCs?

38. Gunnison’s Prairie Dogs Sexually monogamous female squirrels have a 92% chance of successfully giving birth.

39. Gunnison’s Prairie Dogs Sexually monogamous female squirrels have a 92% chance of successfully giving birth. Non-monogamous females have a 100% chance of giving birth

40. Can females detect compatible genes? http://www.pbs.org/wgbh/evolution/library/01/6/l_016_08.html

41. How can a female know which male has successful genes?

42. Females may choose traits, like large displays, that are disadvantageous for male survival.

43. CB 51.36 How can females determine “good” males?

44. CB 51.36 Color: Bright coloring can be correlated with health…

45. CB 51.36 But a male with a mate is judged as being high quality even if he is less colorful

46. How does evolution work for a behaviors such as monogamy? bye monogamous non-monogamous

47. How does evolution work for a behaviors such as monogamy? bye non-monogamous monogamous

48. How does evolution work for a behaviors such as monogamy? After several generations… monogamous non-monogamous

49. Males must choose between having more offspring (more mates) or helping to raise fewer offspring (sperm do not require many resources) • Females choose males that can provide “good” genes or resources for offspring • (eggs, gestation, and/or lactation require high resource input)

50. Am I the only one? Am I better off helping with these kids or should I mate with someone else? Is this the best I can do? Maybe I can find someone with better genes or more genetic diversity.