Transcript Man Seeking Woman - Central Michigan University

Families
Overview of the Day
What is a family?
Evolutionary perspective
Family conflict
mother-fetus, mother-infant, parentchild, sibling
Altruism and inclusive fitness
Discussion of class projects
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?
Mother-Fetus Conflict
Over 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
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
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
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
Conflict over Weaning
Who wants to cease weaning first, mother
or infant?
Why
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
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
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?
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.
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
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
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?
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
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?
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
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?