Lecture 8-9

Kin Selection and Altruism

Why is our psychology so geared towards others - language and empathy

Natural selection works on individuals and not on groups or ecosystems

1. George Williams thought experiment

Imagine a city park inhabited by robins. There is only so much food in the park and if the robins reproduce too much, they will overexploit their food supply and cause their own destruction. Natural selection will act to produce robins that exercise reproductive restraint to keep them in balance with their environment, so as to preserve the species, right? WRONG.

Why? Imagine two variant kinds of robins, one which lowers its reproduction for the good of the group and the other which produces the maximum number of surviving offspring it can. The first type, the altruist, will leave less genetic copies of itself than the second type, the selfish bird. What will happen to the population through time? The selfish ones will predominate.

The implications of this are: 1) all organisms will tend to be selfish; 2) we will not find traits that are for the good of the group, species or planet, at the expense of the individual; 3) organisms are not designed to maintain a population balance with the ecosystem

Outline of lecture

1. Examples of Altruism in Nature

2. Four types of social acts : selfish, altruistic, cooperative, spiteful

3. The concept of the selfish gene

4. Approaches to the understanding of Altruism I: Kinship

A.. Hamilton’s concept of inclusive fitness

B.. Calculating the degree of relatedness

C. The three elements in the calculus of altruism towards kin: Benefits, costs, and degree of relatedness

5. Approaches to the understanding of altruism II: Reciprocity

A. Return effects

B. The prisoner’s dilemma

C. Food Sharing among bats, and humans (reciprocity)

D. The controversy over kinship among Anthropologists

6. Approaches to the understanding of altruism III: Parasitism

7. Spite and its evolution - Revenge killing

8. Conflicts of interests between close relatives.

A. Parent-offspring conflict

B. The case of homicide

9. Selection on virulence the case of aids.

DOES TRUE ALTRUISM EXIST IN NATURE, DO ORGANISMS DO THINGS FOR THE GOOD OF THE SPECIES, GROUP, AT AN EXPENSE TO THEMSELVES, WHY?

1A. “altruism’ in vervets

male defense of group, monkeys

tolerated scrounging

infant gives alarm call

vervet examples, all examples of differential response

1B. Sterile caste in ant and honeybee societies.

1D. The sharing of food in one of the most basic forms of social exchange in all human societies. Among the Ache, all food is shared completely, yet some hunters produce more than 5 times as much food as others. In fact, Ache children are taught to share from very early on. Why is food sharing so important in human societies?

1E. Adoption is also frequently practiced in humans. Why? Among the Efe, babies are passed from person to person, often several times an hour, and they are cared for by many people. And, in most agrarian societies, older children care for younger ones? Why?

1F. Revenge killing is the most commonly reported form of murder in traditional hunting and gathering and agrarian societies. Why risk your life, avenging the life of a dead kinsmen?

1G. Donation of time, goods, services to non-profit enterprises – conservation behavior

2. Four types of social acts : selfish, altruistic, cooperative, spiteful T1

3. The selfish gene - Can we apply the concept of selfishness to the gene? Yes and no. Yes, in the sense that in order to understand the evolution of the gene, we need to understand its effects on its own replication. No, in the sense, that each gene in the genome requires reproduction by the whole organism for its own replication. This is different from groups.

4A. The concept of inclusive fitness - The fitness of a gene depends not only on its effects on the reproduction of the organism in which it is housed but also on its effects on the reproduction of other organisms in which the gene is housed. T2

4b. Kinship determines the probability that the same gene is housed in another organism. The degree of relatedness is calculated through the multiplication of genetic links between organisms and the summation of the different pathways of those links.

4C. Hamilton’s famous equation : Br>C. Benefits to the recipient devalued by the coefficient of relatedness must be greater than the costs to the actor for altruism to be favored.

The case of helping at the nest in birds. Occurs when breeding territories are hard to find. Most helpers are male. T3

Adoption in human societies. Most are kin. In Machiguenga, most adoption is by grandparents and is when there are too many kids. T4

Human helpers at the nest, Efe child care. T5a T5b

Rearing Non-genetic Offspring in the U.S.

The Albuquerque Men study

The sample consists of two sets of interviews. A short interview with about 7100 men included about 2800 Hispanics, 3800 White Anglos and 500 others, and a long detailed interview with about 1200 men.

Most rearing of non-genetic children (fostering) is by men who raise another women’s offspring from a previous marriage T6

Groups for whom kinship is still important raise more kin: Hispanics vs Anglos. T7

When parenting ceases before 18, non-genetic kin receive very little support. T8

Adoption and proximate mechanisms. Machiguenga quote “I raise her as if she were my own”

Garden labor exchange among the Ye’kwana - http://www.multiscope.com/hotspot/factlife.htm

6. Conflicts of interests between close relatives.

A. Parent-offspring conflict -

B. The case of homicide -

Homicide and victimization by kinship. Kin are more frequent victims. However, kin are much less likely to be killed when expectations, based on frequency of interaction, are taken into account, and also when blood kinship is distinguished from affinal kinship.

5. Virtually all aspects of social life in prestate societies are governed by kinship rules, and even much of social life in state societies is dictated by kinship. However, many anthropologists think that this has nothing to do with kin-selected altruism, because kinship is defined differently in different societies, and the concept of fictive kin is ubiquitous. Our best understanding of these two facts is that humans preferentially associate with kin for the same reasons that other organisms do, but the importance of reciprocity in human societies often leads to the extension of social kinship to individuals with whom we share reciprocal aid.