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Families

Families. Overview of the Day What is a family? Evolutionary perspective Family conflict mother-fetus, mother-infant, parent- child, sibling Altruism and inclusive fitness Discussion of class projects. What is a Family? Why did Families Evolve? .

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Families

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  1. Families Overview of the Day What is a family? Evolutionary perspective Family conflict mother-fetus, mother-infant, parent- child, sibling Altruism and inclusive fitness Discussion of class projects

  2. What is a Family? Why did Families Evolve? • Groups where offspring continue to interact with their parents regularly into adulthood • simple families (nuclear) • extended families • Only 3% of bird and mammalian species form families • what are the benefits and costs?

  3. Mother-Fetus ConflictOver Mother’s food • Pregnancy sickness: nausea, vomiting, and food aversions and cravings during pregnancy • Functions of pregnancy sickness • prevent fetus from being exposed to teratogens (toxins that are harmful to developing fetus) • Pregnancy sickness is associated with: • Fewer miscarriages • Fewer fetal deaths

  4. Food Aversions and Cravings • Aversions • Meat • Vegetables • Beverages containing caffeine (coffee, tea) • Cravings • Fruit and fruit juice • Sweets • Grains and starches • Dairy and ice cream

  5. Mother-fetus Conflict over Mother’s Blood Supply • Placental cells destroy arteriolar muscles which regulate blood supply and secrete substances that increase constriction of arteries • Constriction results in: more blood to fetus but high blood pressure to mom (excessive HBP--> preeclampsia) • Moderately HBP during pregnancy is associated with lower fetal mortality

  6. Mother-Fetus Conflict over Mother’s Glucose • Fetus secretes hPL (human placental lactogen) that ties up mother’s insulin • Mother’s glucose goes up, providing more to fetus • Mother then secretes more insulin and fetus secretes more hPL • If mother cannot respond with enough insulin, she develops gestational diabetes

  7. Conflict over Weaning • Who wants to cease weaning first, mother or infant? • Why

  8. Sibling Conflict • 50 % relatedness • Compete with each other for resources • MZ twins exhibit less conflict • Half sibs exhibit more conflict • Why do parents teach children to share? • What hurts your relative hurts your fitness

  9. Other Conflicts • Finicky about food • Adult and child nutrition needs are different • Children more susceptible to teratogens • Bedtime • Night was dangerous, safer with mom • Higher incidents of SIDS among children who sleep alone

  10. Parents and Teenagers • Adolescent rebellion • Changes in frontal cortex • Develop own identity • Perhaps a motivating force for leaving the nest • Can you think of possible evolutionary explanations for the reckless behavior of many teenagers?

  11. Kin Selection and Hamilton’s Rule • Kin Selection: Altruism toward kin • Hamilton’s Rule: Natural selection favors mechanisms for altruism when c < rb • where c = cost to actor • r = relatedness of actor and recipient • b = benefits to recipient • Another relevant variable is reproductive value, v.

  12. Altruism and Inclusive Fitness • Altruism: helping other without consideration of one’s own welfare • Inclusive fitness: the number of copies of one’s genes that appear in current or subsequent generations of offspring and kin’s offspring • Altruism increases inclusive fitness

  13. Who Would You Help? • Jump in a river to save • ___ bothers • ___ cousins • 1 < .5(3); 1 < .125(9) • How about a non-relative? • Reciprocal altruism: giving help with the expectation that the other will return the favor in the future (tit for tat). Evolutionary stable strategy

  14. Who do People Help the Most? • Ground squirrel alarm • LA study: help was a linear function of relatedness • Studies of wills: 92.3% of people leave money to kin • Who helps more: maternal or paternal uncles and aunts?

  15. The Grandmother Hypothesis • Why do women live beyond menopause? • They contribute substantially to the welfare of grandchildren • Grandmothers share 25% of their genes with their grandchildren

  16. Altruism in The Road North • What concepts from EP could explain why Claveles Picero gave her young son to Senora Dermoths’ charitable mission? • What concepts from EP could explain why Jesus Picero was so insistent that they travel 70 kilometers to look for his grandson? • Why did the mother of Jesus’ youngest son’s daughter drop her (the daughter) off in a bundle on the father’s barracks door?

  17. The Evolution of Marriage and the Benefits of Marriage • Why does the institution of marriage exist in every society, and why has it existed for thousands of years? • It works--not perfectly, but better than alternatives devised so far • Child rearing and paternity uncertainty • Other benefits: married adults are less likely than single adults to die young, develop physical disabilities, or suffer psychological and emotional illnesses

  18. Summary and Projects • What is a family? • Family conflict • Altruism and inclusive fitness • Your projects: • Focus • Question that can be addressed with data • What type of data will you collect? • How will your data answer your question?

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