Overview of Lecture: Sex & Reproduction. Read: Text ch 46 (review ch 13) Bullet Points: • Sex & Reproduction • Why Have Sex? • Parthenogenseis • Sexual Selection • Sexual Conflict • Human Mating Systems • Signaling & Mate Choice • Evolutionary Psychology • Parental CareIn a population of parthenogenetic females cloning selves: the pop. can produce babies faster – everyone’s a mom; & each baby reproduces 100% of a mom’s genes, not 50%; With sex, isolated mutations at diff loci in diff individuals can be combined in one individual: beneficial mutations can interact synergistically & deleterious mutations can be purged in batches – both processes can speed adaptation and select for sexual recombination. But babies, families & the pop genetically more homogeneous; less variable ecology, more vulnerable to coevolving parasiteshttp://www.pbs.org/wgbh/evolution/sex/mating/index.htmlBy Nancy Touchette; April 23, 2004 Researchers in Japan have shown for the first time that female mice can reproduce without help from the other half of the species.Environment includes social env as well as ecological env. Males & females are in different social (mating) env’s. Parasitic male anglerfishfemales males There appears to be stronger selection on than on to mate more than once. mean # offspring 0 120 0 1 2 3 # mates Fruit flies: - eager ? - choosy ?… courtship alone was sufficient to reduce male life span. Mating itself and production of seminal fluid and sperm, on the other hand, did not seem to be costly … p (still alive) Mounting attempts may be an indicator of an altered metabolic rate or hormonal status {stress?} that renders the males more susceptible to death. Cordts R, Partridge L. 1996. Courtship reduces longevity of male Drosophila melanogaster ANIM. BEHAV. 52: 269-278.The cost of mating to females may therefore represent a side-effect of evolutionary conflict between males Neuroscience: Love hangover. {identifies receptor to sex-peptide} Leslie C. News and Views Nature 451, 24-25 (3 January 2008) Sex-peptide is the molecular basis of the sperm effect in Drosophila melanogaster. Liu H, Kubli E. Proc Natl Acad Sci U S A. 2003 Aug 19;100(17):9929-33. The cost of mating rises nonlinearly with copulation frequency in a laboratory population of Drosophila melanogaster. Kuijper et al. 2006 J Evol Biol 19:1795-1802Does size dimorphism in humans suggest anything about ancestral mating systems? Across primates, harem size is correlated w/ dimorphism Comparing human dimorphism (1.1) to pattern in primates suggests humans evolved dominance and mating system with at least a little polygynyBBC. 1.5m Chinese 'descendants of one man' Over 1.5 million served. Not by McDonalds but Giocangga, the grandfather of the founder of the Qing dynasty, Recent genetic research suggests that over 1.5 million Chinese men are the direct descendants of this one single man. ... the average Chinese man at the time of Giocangga would only have around 20 descendants living today.Chimps are not size dimorphic; males do not control access to harem Gorillas are very dimorphic; males control access to harem Humans slightly dimorphic; slightly polygynous; do guard mate(s) Inverse correlation between size dimorphism vs testicle size; Human mating system seems to have evolved w/ some competition for access to copulation; what about sperm competition? Big mystery: Why human male penis so big? More on Primate sexual dimorphism & mating system (from The Third Chimpanzee, Diamond 1992) 3.4 3.4Human female breasts padded w/ fat, much larger than necessary to nourish babies. Hyp: Large breasts advertise youth, health & high repro. potential. Angier (1999) claims male obsession w/ breasts is maladaptive Consider female choices: Males find ‘shapely’ breasts attractive.MACHINE MEASURES BEAUTY OF FACE (Feb, 1933)Abstract: Psychological evidence suggests that sex differences in morphology have been modified by sexual selection so as to attract mates (intersexual) or intimidate rivals (intrasexual selection): Low waist-hip ratio is sexually attractive in women ... The male beard is not obviously related to phenotypic quality ... Darwinian aesthetics: sexual selection and the biology of beauty. Grammer et al. Biological Reviews 78 (3): 385-407 AUG 2003Waist-hip ratio in women is often considered a key feature in physical attractiveness. Measured directly from this image, the frontal WHR of the model in this image is approximately 0.69.The left-hand composite face was from women with the highest oestrogen levels, and was judged more attractive than the composite on the right, from women with the lowest levels of oestrogen. These are the computer-generated composite faces of the 10 women w/ highest & lowest oestrogen levels - which do you find more attractive? (Image: Miriam Law Smith) ML Smith & colleagues photographed 59 women, aged 18-25, every week for six weeks. ... they provided a urine sample for hormone analysis and gave information on their menstrual cycle. None wore make-up, nor took the contraceptive pill. The photographs were rated by 14 men and 15 women, for attractiveness, health and femininity. The group also rated two composite face images of the 10 women with the lowest peak-oestrogen levels & the 10 women with the highest levels (see image). {note skin color in photos & consider function of makeup}Human oestrus October 10, 2007 By Abigail Goldman Science says lap dancers send 'signals,' rake in cash The earnings of the normally-cycling (non pill-using) lap dancers nearly doubled to US$350 per shift around the times when they ovulated ... as they approached menstruation ... earnings declined to about US$200 per shift.The results indicate that females exhibit (1) a preference for a male face on the masculine side of average, (2) a shift toward a more masculine male face preference during the high-risk phase of their menstrual cycle {-29 frames} The results are interpreted as support for a hormonal theory of facial attractiveness, whereby perceived beauty depends on an interaction between displayed hormone markers {masculinity} and