Evolution/Sociobiology

Question 1

Pros and cons of categorical thinking

Answer 1

1. Helps you remember and recognize an example of a group.
2. You tend to see members of a group as more similar than they actually are and members of different
   groups as more different than they actually are (color perception example).
3. Myopic focus on individual categories (buckets) by leading thinkers of the past has led to disastrous
   outcomes

Question 2

Evolution (change over time) caused by a number of things. We focus on the big one: natural
selection. Requires what three conditions?
Then what happens?

Answer 2

1. Heritability (DNA)
2. Variability (mutation)
3. Differential fitness (success in leaving progeny)
   then happens:
4. Versions that confer more fitness will become more prevalent over time

Question 3

Sociobiology is the study of the evolution of behavior. What are the three core explanatory pieces you should be able to apply to a wide range of behavior?

Answer 3

1. Individual selection. “A chicken is an egg’s way of making another egg.” -Samuel Butler
2. Kin selection/inclusive fitness. “I will lay down my life for 2 brothers or 8 cousins” -JBS Haldane
3. Reciprocal altruism.

Question 4

Five pieces of evidence for evolution?

Answer 4

1. Observable over past 100 years in short-lived species like staph bacteria & penicillin resistance
2. Fossil record shows tons of intermediate forms
3. Genetic evidence: we share huge percentages of our genomes with our closest evolutionary ancestors,
   and less the further you go back in time to most recent common ancestor
4. Geographic distribution of species: relatives are bunched together in space
5. Unintelligent design: vestigal structures like leg bones in dolphins, pyramidal system for finger
   movement

Question 5

In our class: natural selection and sexual selection are different (sometimes opposing) forces.
How do they apply to individual selection?

Answer 5

1. Natural: adaptedness to surviving in the environment

2. Sexual: adaptedness at attracting a mate

Question 6

In our class: natural selection and sexual selection are different (sometimes opposing) forces.
How do they apply to kin selection (inclusive fitness)?

Answer 6

1. Natural: Engage in behaviors that allow related individuals to survive and reproduce
2. Sexual: Work to make related individuals seem attractive to potential mates

Question 7

In our class: natural selection and sexual selection are different (sometimes opposing) forces.
How do they apply to cooperation/altruism?

Answer 7

1. Natural: non-related hunters cooperating to get game they couldn’t get alone.
2. Sexual: cooperatively making a non-relative more attractive to mates

Question 8

How do you calculate degrees of relatedness?

Answer 8

1. 50% gene-variant similarity with parent or full sibling. 25% with grandparent. 25% with (biological) aunt/uncle. 12.5% with great grandparent, etc.
2. Each “line” in the family tree that you traverse typically halves the number of genes you share with the next individual.

Question 9

What typically characterizes species that demonstrate reciprocal altruism?

Answer 9

“Species that are social, long-lived enough and in sufficiently stable groups so that individuals interact with each
other more than once (how else can the reciprocity occur?), smart enough to recognize individuals and, critically, smart enough to try to cheat at the reciprocity when it’s possible to get away with it (i.e., to not reciprocate an altruistic act), and smart enough to spot someone trying to cheat against them.”

Question 10

What is Axelrod’s famous winning strategy? What does even better under some conditions? (game theory : prisoner’s dilemma of when to cooperate and when to defect)

Answer 10

1. Tit for tat. Will lose battles but win wars. Will lose to cheaters, but pairs of TfT will win more than
   cheaters ever will.
2. Better with forgiving tit for tat (less prone to signal errors)
3. Pavlov can exploit forgiving tit for tat

Question 11

What are five examples of Tit for tat or interesting elaborations?

Answer 11

1. Vampire bats (TfT)
2. Stickleback fish (TfT)
3. Gender switching fish who defect if the other defected (TfT)
4. Cowardly lions who are good hunters (different domains of contribution)
5. Huge naked mole rats plugging up holes (different domains of contribution)

Question 12

Related to kin selection: the greenbeard effect. What is it?

Answer 12

1. Not about recognizing kin, necessarily, but instead just one gene that allows for
2. Recognition of the gene in other individuals
3. Cooperation with other individuals that have that gene

Question 13

Related to cooperation: rock-paper-scissors equilibrium

Answer 13

1. Actually restraint from competition. Not true altruism.

Question 14

How does cooperation/altruism start?

Answer 14

1. Founder population cooperates on a basis of kin selection. Then when re-integrated into large population, they keep “winning the war” and cooperation crystalizes outward or non-cooperation is driven extinct.

Question 15

Pair Bonding and Tournament Species
How do we explain imprinted genes (both father and mother)?
What happens when these go unchecked?

Answer 15

1.Father’s imprinted genes cause a more “selfish” infant that grows a lot, suckles lots of nutrients, etc. at
the expense of the female’s future reproductive success. Tournament species males are interested in mating with many females until they get kicked out.

Choriocarcinoma.

2.Mother’s imprinted genes do the opposite. Slow down growth and nutrient uptake. She’s equally
interested in the success of future progeny as much as this one.

Egg won’t implant

3.Exemplify inter-sexual competition via parent-offspring conflict. Higher in tournament species.

Question 16

How do we explain competitive infanticide?

Answer 16

1. Definitely not for the good of the species!
2. When the average tenure of the head male is shorter than the average interbirth interval in females.
3. Males operating under individual selection: wipe out other infants so mothers can be impregnated (tie to oxytocin
   - nursing - fertility suppression - endocrinology foreshadowing), plus less competition for his future offspring.
4. Females coping via individual selection principles: smell of new male causes spontaneous miscarriage because it
   doesn’t make sense to have an offspring that will be killed. Save on pregnancy costs and get pregnant with the
   new male. Female still has 50% genetic interest in her offspring whether it’s old male or new.
5. Females coping via kin selection: defending their children up to a point (when would they lay down their life?),
   also faking pseudo-estrus to fool the new head male into not forcing them to spontaneously miscarry from harassment.

Question 17

What are some further behavioral examples explained well by sociobiology?

Answer 17

1. Kidnapping by male baboons (and not kidnapping when high-ranking male just joined the troupe)
2. Relatedness in dominance hierarchies. Females inherit their rank
3. Sex ratios.
4. Males are more “expensive” but high ranking tournament species females will gamble on a son instead of a daughter. What’s the proximate mechanism here? Higher-ranking females have better nutrition so sons will be more likely to be carried to term.
5. Sex ratios will stabilize over time near 50-50.
6. Paying attention to alarm calls as a function of relatedness
7. Male-male cooperation
8. Instances of polyandry (multiple males leading a harem).
   Usually adelphic (by related males). Includes humans (see
   traditional Tibetan marriage patterns).

Question 18

Why would you mate with relatives? (behavioural examples explained well with sociobiology)

Answer 18

1. Share more genes with them so more of your genes make it into the next generation. Great!
2. But if they’re too closely related than recessive disease-causing alleles are likely to be inherited and cause disease. Not so great!
3. Where does the “optimal” mating occur, according to the Helgason “Kinship and Fertility” reading? 3rd or 4th cousin matings produce the most fertile offspring.

Question 19

How do chimps vs. baboons differ in which gender leaves the troupe? What consequences does that have? (behavioural examples explained well with sociobiology)

Answer 19

1. Baboons: males leave the troupe. Females stay and are more related.
   i. Males kill each other more
2. Chimps: females leave the troupe. Males stay and are more related.
   i. Males band together and often kill neighboring males. This is protowarfare and genocide.

Question 20

Group selection. Is it valid? What version is invalid?

Answer 20

1. Not for the good of the species.
2. Yes multi-level selection.
   a. Founder populations evolve cooperation based on kin selection, and can then outcompete other groups they are re-integrated with.
   b. Situation of A<b>BB.
   c. Parochial altruism is the phenomenon of cooperating with an in-group against an out-group, regardless of
   kinship. Like WWII.</b>

Question 21

What are some common patterns of human behavior across cultures and time?

Answer 21

1. Males more violent than females
2. Hierarchical systems
3. Emphasis on kinship
4. Polygamy (most cultures contain polygamy; most individuals within those cultures practice (serial) monogamy)

Question 22

What are four criticisms of sociobiology?

Answer 22

1. Sociobiology says behaviors are heritable.
   a. Criticism: What is your proximate mechanism? Where’s the gene? What protein does it code for?
   That’s the real basis of evolution.
2. Sociobiology says every social behavior is an adaptation.
   a. Criticism: This is the adaptationist fallacy that everything is adaptive. You’re making up just-so stories! What about spandrels?
3. Sociobiology says that evolutionary change happens continuously in small incremental steps - gradualism. Evolution, not revolution.
   a. Criticism: What about punctuated equilibrium? Fossil record shows periods of stasis and periods of rapid change. Tiny adaptations don’t make a difference.
4. And political criticisms. “Oh the conclusions you draw scientifically just happen to justify the hierarchies and inequities our society faces and which you (Southern, white scientists) benefit from.”