Day 17 March 22nd Chapter 9

Day 17 March 22nd Chapter 9

I’m still grading your retakes – it’s taking more to export them, average them, then

re-upload them than I thought

Prepared Learning

Behaviors that are learned easily and by all (or nearly all) individuals

Snake-fearing behavior of monkeys Acquisition of language in humans

Animals don’t consciously try to maximize their reproductive success, yet they behave as if they do?

How do they do it?

Rules of Thumb

Relatively easy-to-follow responses to cues that reliably lead to a desired outcome

Pleasure = Repeat

Rules of Thumb

Pleasures, incentives, and reproductive success

Not necessary for the animal to be consciously seeking that outcome

How do we know?

Tricking animals

9.5 A general theory of “kindness” helps explain the evolution of apparent acts of altruism.

Does unconditional love exist in the animal kingdom?

Altruistic behaviors—behaviors that come at a cost to the individual doing the behavior while benefiting the recipient.

Darwin

Natural selection generally works to produce selfish behavior.

Altruistic-appearing behavior is common.

Fatal to his theory?

Apparent Acts of Altruism

Kindness toward close relatives: kin selection (population survival)

Kindness toward unrelated individuals: reciprocal altruism (help you in the future)

Hamilton’s Rule

Altruistic-appearing behavior will occur when the benefits to close relatives are greater than the cost to the individual performing the behavior.

They are really acting in their own genes’ best interests.

According to Hamilton’s rule, if an individual could only help one person, who would they prefer to help?

1. Son with a flat tire2. Aunt with a flat tire3. Cousin with a flat tire4. Stranger with a flat tire

According to Hamilton’s rule, if an individual could only help one person, who would they prefer to help?

1. Son with a flat tire2. Aunt with a flat tire3. Cousin with a flat tire4. Stranger with a flat tire

End day 18

Who are people most likely to bequeath money to upon their death?

Redefining an Individual’s Fitness

Direct fitness• An individual’s total reproductive output

Indirect fitness• The reproductive output brought about

by altruistic behaviors toward close kin Inclusive fitness

• The sum of an individual’s indirect and direct fitness

Conflicts

Because different individuals do not share all of the same alleles, we should always expect some conflict.

Example: gestational diabetes – mother is producing a THOUSAND times the normal amount of insulin

9.7 Apparent altruism toward unrelated individuals can evolve through reciprocal altruism.

Vampire Bats

In many cases, individuals give blood to unrelated individuals.

How might this behavior have arisen?

First, -recognize more than a hundred distinct individuals. Second, -receive blood donations from non-relatives reciprocate significantly more than average. And third, -not familiar with each other (and do not have a history of helping each other) generally do not regurgitate for each other.

Are they repaid the favor?

Reciprocal AltruismStoring goodwill

“I’m doing this for you so that you will do it for me in the

future”

We’re all born with a spare kidney, yet virtually no one donates theirs to non-relatives in need.

Why?

Certain Conditions Must Be Met

1) Repeated interactions among individuals

2) The benefits to the recipient must be significantly greater than the costs to the donor.

3) The ability to recognize and punish cheaters

Why are humans among the only species to have friendships?

Why is it easier to remember gossip than

physics equations?- it helps us survive if we recognize cheaters

9.8 In an “alien” environment, behaviors produced by natural selection may no longer be adaptive.

Behaviors favored by natural selection over evolutionary time can cause individuals to behave in a way that reduces their fitness. Belding’s ground squirrels Craving high-fat foods Donations to refugees

Feels good to help

Good Karma?

9.9 Selfish genes win out over group selection.

Does evolution ever lead to behaviors that are for the good of the species or population, while being detrimental to

the individual?

If we donate money to “save the children” or another international charity, is this a purely altruistic behavior?

1. Strongly agree2. Agree3. Neutral4. Disagree5. Strongly

disagree

9.10 There are big differences in how much males and females invest in reproduction.

Russian woman had 69 children (in 27 pregnancies).

888 offspring produced by a male (the Emperor of Morocco from 1672 to 1727)

Definition of “Male” and “Female”

A female produces the larger gamete. A male produces the smaller gamete.

The mother’s material contribution to the offspring exceeds the father’s.

Evolution of Differences in Male/Female Behaviors

1) Extent of energetic differences in the reproductive investment.

Why do males usually compete for females rather than the opposite?

About how much greater is the male reproductive output with three mates when compared to the female?

1. 2 times greater2. 4 times greater3. 6 times greater4. 8 times greater5. 10 times

greater

About how much greater is the male reproductive output with three mates when compared to the female?

1. 2 times greater2. 4 times greater3. 6 times greater4. 8 times greater5. 10 times

greater

Differences in Reproductive Investments

Fertilization within the female

Lactation in female mammals

Offsets and Reversals in Reproductive Investment

Examples: Birds

• Gestation external

• No lactation

Examples: Fish and amphibians

• External fertilization

Offsets and Reversals in Reproductive Investment

Evolution of Differences in Male/Female Behaviors

1) Extent of energetic differences in the reproductive investment

2) Paternity uncertainty• also has profound influence on reproductive

behavior