Kevin MacDonald, Ph.D.
CSULB, Department of Psychology
Psychology 346IC
Selection Levels
FITNESS OF WHAT?
INTRA-SPECIFIC COMPETITION (COMPETITION WITHIN SPECIES) IS UBIQUITOUS.
E.G., HAMADRYAS BABOON: MALES COMPETE WITH OTHER MALES TO ESTABLISH HAREM AND PUNISH HAREM FEMALES WHO ATTEMPT TO MATE WITH OTHERS.
GENES MAKING A MALE BABOON BEHAVE IN THE INTERESTS OF ALL MEMBERS OF THE GROUP WHILE MAKING HIM LESS COMPETITIVE WITH OTHER MALES OR UNCONCERNED ABOUT FEMALES MATING WITH OTHER MALES WILL LEAVE FEW COPIES OF THAT GENE IN LATER GENERATIONS. HE WILL NOT REPRODUCE AS WELL AS SELFISH BABOON..
WYNNE-EDWARDS (1962): ANIMALS ARE DESIGNED TO MAXIMIZE THE FITNESS OF THE SPECIES.
E.G., BIRDS PHYSIOLOGICALLY ABLE TO LAY MANY MORE EGGS THAN THEY ACTUALLY LAY (FINCHES: 71 EGGS IN 72 DAYS). THEY RESTRAIN THEMSELVES 'FOR THE GOOD OF THE SPECIES' (PREVENT OVERPOPULATION). WYNNE-EDWARDS ARGUED THAT SPECIES WITHOUT THIS ABILITY WOULD DIE OUT.
WYNNE-EDWARDS' VIEW IMPLIES NATURAL SELECTION BETWEEN GROUPS AND GROUP EXTINCTION: GROUPS THAT FAIL TO REGULATE THEMSELVES BY CUTTING BACK ON REPRODUCTION GO EXTINCT.
PROBLEMS WITH GROUP SELECTION:
1.) HOW CAN GROUPS KEEP OUT SELFISH CHEATERS?
IT WOULD ALWAYS BE TO AN INDIVIDUAL'S ADVANTAGE TO ACT SELFISHLY.
'SELFISH GENES' ALWAYS SPREAD WITHIN GROUPS AT THE EXPENSE OF ALTRUISTIC GENES.
2.) WYNNE-EDWARD'S EXAMPLES AND OTHER EXAMPLES OF BEHAVIOR THAT SEEMS ALTRUISTIC CAN BE EXPLAINED BY NATURAL SELECTION ACTING ON INDIVIDUALS, NOT GROUPS.
FOR EXAMPLE, BREEDING RESTRAINT IS ILLUSORY. MOST COMMON CLUTCH SIZE IS MOST PRODUCTIVE. Higher clutch sizes actually have fewer fledged birds.
DEFINITIONS:
COEFFICIENT OF RELATEDNESS (r) = PERCENTAGE OF GENES IDENTICAL BY DESCENT
PARENT-OFFSPRING r = 1/2; I.E., THE PROBABILITY OF MY OFFSPRING HAVING ANY ONE OF MY GENES BY DESCENT= 1/2
PARENT-GRANDCHILD: R = 1/4
SELF-FIRST COUSIN: R= 1/8
INCLUSIVE FITNESS = RS OF SELF + (r X INCREASE IN KIN'S RS AS A RESULT OF SELF'S INFLUENCE)
EXAMPLE: IF I HAVE 3 CHILDREN AND I ALSO HELP MY SISTER SO THAT SHE CAN RAISE 2 MORE CHILDREN THAN SHE OTHERWISE COULD,
IF = 3 + (.5 × 2) = 3 + 1 = 4
HAMILTON'S RULE: IN ORDER FOR HELPING MY KIN TO BE ADVANTAGEOUS TO ME, MY COST (c) MUST BE LESS THAN THE BENEFIT TO MY KIN MULTIPLIED BY r.
c < r b
EXAMPLE: IT MAKES SENSE FOR ME TO HELP MY SISTER IF
c < rb c < .5b (r for me and my sister = .5)
THEREFORE, IT PAYS ME TO RAISE ONE LESS CHILD IF BY DOING SO I CAN HELP MY SISTER RAISE MORE THAN 2 EXTRA CHILDREN:
c < .5(b) 1 < .5(3)
1 < .5(4) ... etc.
IF MY HELP ALLOWS MY SISTER TO RAISE EXACTLY 2 EXTRA CHILDREN, IT MAKES NO DIFFERENCE IN INCLUSIVE FITNESS IF I HAVE MY OWN CHILD OR HELP MY SISTER
c < .5b 1 = .5(2)
NEPOSTIC STRATEGIES
RICHARD ALEXANDER: 'ACCORDING TO INCLUSIVE-FITNESS THEORY, WE SHOULD HAVE EVOLVED TO BE EXCEEDINGLY EFFECTIVE NEPOTISTS, AND WE SHOULD HAVE EVOLVED TO BE NOTHING ELSE AT ALL.'
MONKEYS: SIBLING SOLIDARITY: MUTUAL GROOMING, MUTUAL DEFENSE; DISCRIMINATION OF MORE DISTANT RELATIVES.
HUMANS: PARENTS;
CHINESE EUNUCHS;
RENAISSANCE POPES;
KINSHIP AS BASIS OF HUMAN SOCIAL ORGANIZATION: E.G., CLANS OF RELATED MALES
LEVELS OF SELECTION
1. GENES: IF SELECTION ACTS AT THE LEVEL OF THE GENE, THEN THERE IS COMPETITION WITHIN THE GENOME FOR WHICH GENES WILL BECOME PART OF FERTILIZED EGG = INTRA-GENOMIC CONFLICT.
EXAMPLE: 'MEIOTIC DRIVE'
ALTHOUGH THERE ARE SOME EXAMPLES OF INTRA-GENOMIC CONFLICT, THERE IS A 'PARLIAMENT OF GENES' WITHIN EACH INDIVIDUAL: EACH GENE HAS THE SAME PROBABILITY OF BEING REPRESENTED IN THE FERTILIZED EGG.
GENES WITHIN PEOPLE ARE DESIGNED TO MESH TOGETHER BECAUSE THEY SHARE A COMMON FATE IN THE INDIVIDUAL.
2. INDIVIDUALS: IF SELECTION ACTS AT THE LEVEL OF THE INDIVIDUAL, THEN THERE IS COMPETITION BETWEEN INDIVIDUALS FOR RS
THIS IS THE PROBABLY THE MOST IMPORTANT LEVEL. WE HAVE MOST EVIDENCE FOR COMPETITION AMONG INDIVIDUALS WITHIN SPECIES. OUR ADAPTATIONS ARE MAINLY DESIGNED BY INDIVIDUAL-LEVEL SELECTION
3. GROUPS: IF SELECTION ACTS AT THE LEVEL OF THE GROUP, THEN THERE IS COMPETITION BETWEEN GROUPS FOR RS AND INDIVIDUALS WITHIN GROUPS SHARE A COMMON FATE.
CENTRAL THEORETICAL PROBLEM: CAN ALTRUISTIC GROUPS EVOLVE?
COMMON WISDOM: SELFISH INDIVIDUALS ALWAYS OUT-REPRODUCE ALTRUISTS WITHIN GROUPS, SO THAT IT IS UNLIKELY THAT ALTRUISTIC GROUPS COULD EVOLVE.
BUT HUMAN (AND PERHAPS SOME ANIMAL) GROUPS CAN EXCLUDE OR PUNISH 'CHEATERS' (NON-ALTRUISTS) WHO DEFECT FROM GROUP GOALS TO PURSUE INDIVIDUAL INTERESTS.
EXAMPLE: MILITARY UNIT
