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

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Presentation on theme: "Families Overview of the Day What is a family? Evolutionary perspective Family conflict mother-fetus, mother-infant, parent- child, sibling Altruism and."— Presentation transcript:

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? zGroups where offspring continue to interact with their parents regularly into adulthood ysimple families (nuclear) yextended families zOnly 3% of bird and mammalian species form families ywhat are the benefits and costs?

3 Mother-Fetus Conflict Over Mother’s food zPregnancy sickness: nausea, vomiting, and food aversions and cravings during pregnancy zFunctions of pregnancy sickness yprevent fetus from being exposed to teratogens (toxins that are harmful to developing fetus) zPregnancy sickness is associated with: yFewer miscarriages yFewer fetal deaths

4 Food Aversions and Cravings zAversions yMeat yVegetables yBeverages containing caffeine (coffee, tea) zCravings yFruit and fruit juice ySweets yGrains and starches yDairy and ice cream

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

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

7 Conflict over Weaning zWho wants to cease weaning first, mother or infant? zWhy

8 Sibling Conflict z50 % relatedness zCompete with each other for resources zMZ twins exhibit less conflict zHalf sibs exhibit more conflict zWhy do parents teach children to share? yWhat hurts your relative hurts your fitness

9 Other Conflicts zFinicky about food yAdult and child nutrition needs are different yChildren more susceptible to teratogens zBedtime yNight was dangerous, safer with mom yHigher incidents of SIDS among children who sleep alone

10 Parents and Teenagers zAdolescent rebellion yChanges in frontal cortex yDevelop own identity yPerhaps a motivating force for leaving the nest zCan you think of possible evolutionary explanations for the reckless behavior of many teenagers?

11 Kin Selection and Hamilton’s Rule zKin Selection: Altruism toward kin zHamilton’s Rule: Natural selection favors mechanisms for altruism when c < rb ywhere c = cost to actor yr = relatedness of actor and recipient yb = benefits to recipient zAnother relevant variable is reproductive value, v.

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

13 Who Would You Help? zJump in a river to save y___ bothers y___ cousins z1 <.5(3); 1 <.125(9) zHow about a non-relative? yReciprocal 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? zGround squirrel alarm zLA study: help was a linear function of relatedness zStudies of wills: 92.3% of people leave money to kin zWho helps more: maternal or paternal uncles and aunts?

15 The Grandmother Hypothesis zWhy do women live beyond menopause? zThey contribute substantially to the welfare of grandchildren yGrandmothers share 25% of their genes with their grandchildren

16 Altruism in The Road North zWhat concepts from EP could explain why Claveles Picero gave her young son to Senora Dermoths’ charitable mission? zWhat concepts from EP could explain why Jesus Picero was so insistent that they travel 70 kilometers to look for his grandson? zWhy 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 zWhy does the institution of marriage exist in every society, and why has it existed for thousands of years? yIt works--not perfectly, but better than alternatives devised so far xChild rearing and paternity uncertainty xOther 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 zWhat is a family? zFamily conflict zAltruism and inclusive fitness zYour projects: yFocus yQuestion that can be addressed with data yWhat type of data will you collect? yHow will your data answer your question?


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