Psychology 346IC
Evolutionary Theory of Sex
1.) MALES DEFINED AS SEX WITH SMALL GAMETES, FEMALES ARE SEX WITH LARGE GAMETES2.) FEMALES TEND TO INVEST MORE IN REPRODUCTION THAN MALES.
TYPICAL MAMMALIAN FEMALE: PREGNANCY, LACTATION, CAREGIVING'VERY HIGH
COST IN TIME AND ENERGY
TYPICAL MAMMALIAN MALE: SPERM'VERY LOW COST
3.) ECONOMICS 101: WHEN YOU HOLD VALUABLE RESOURCES, YOU DON'T GIVE THEM AWAY.
FEMALES EXPECTED TO BE SELECTIVE
FEMALES WANT:
MALES WHO WILL INVEST IN OFFSPRING,
MALES WITH GOOD GENES, HIGH SOCIAL STATUS,
ETC.
4.) MALES MUST COMPETE FOR FEMALES.
MAIN OBSTACLE ARE OTHER MALES:
ELEPHANT SEALS: DEFEATING MALES IN COMBAT
CHINESE EMPERORS: CONTROLLING MALES AND FEMALES
MOVIE STARS, SUCCESFUL HUNTERS in hunter-gatherer societies,
AND RICH
MEN everywhere: ATTRACTIVE TO FEMALES (The Anna Nicole
Smith
phenomenon)
MALES HAVE MORE TO GAIN BY BEING HIGH ON BEHAVIORAL APPROACH SYSTEMS (AGGRESSION, RISK-TAKING, SENSATION-SEEKING, SOCIAL DOMINANCE): SUCCESSFUL MALE CAN MATE POLYGYNOUSLY, SUCCESSFUL FEMALE CAN MATE ONLY ONCE.
FEMALES ADOPT A MORE CONSERVATIVE STRATEGY:
HIGHER ON FEAR, BEHAVIORAL INHIBITION.
FEMALES ALSO EXPECTED TO BE HIGHER ON NURTURANCE/LOVE SYSTEM AS MATE
DISCRIMINATION SYSTEM AND BECAUSE OF ITS ROLE IN NURTURANCE.
SEXUAL SELECTION
SEXUAL SELECTION: DIFFERENTIAL REPRODUCTION DUE TO ADVANTAGES IN MATING (NOT SURVIVAL). E.g., antlers on a male deer facilitate defeating other males in combat and therefore increase access to females.
INTRASEXUAL SELECTION: COMPETITIVE ABILITIES WITHIN SEX; E.G., MALE FIGHTING ABILITY: WINNERS MATE MORE FREQUENTLY; LEADS TO EVOLUTION OF MALE HORNS, ETC.
INTERSEXUAL SELECTION: SPECIALIZED SIGNALS THAT APPEAL TO THE OPPOSITE
SEX
1. SIGNALS INDICATING ANIMAL WILL BE A GOOD PARENT. E.G., FEMALES CHOOSE
HIGH-INVESTING MALES; MALES CHOOSE NURTURANT FEMALES
2. SIGNALS INDICATING 'GOOD GENES'; E.G., FEMALES OR MALES CHOOSING
HEALTHY PARTNERS
INTRASEXUAL SELECTION INVOLVES TRADE-OFFS BETWEEN MATING
EFFORT AND PARENTING EFFORT.
MATING EFFORT: EFFORT EXPENDED TO ATTRACT MATES
PARENTING EFFORT: EFFORT EXPENDED TO REAR OFFSPRING
ON AVERAGE, FEMALES EXPEND GREATER PARENTING EFFORT, BECAUSE THEY DO
NOT GAIN FROM INCREASED MATINGS.
ON AVERAGE, MALES EXPEND MORE MATING EFFORT BECAUSE THEY GAIN MORE
FROM ADDITIONAL MATINGS.
HOWEVER, SOME MALES GAIN MORE FROM DEVOTING MORE TIME AND ENERGY
TO MATING THAN OTHERS.
E.G., MALES WITH FEW MATING OPPORTUNITIES SHOULD BE WILLING
TO DEVOTE MORE ENERGY TO PARENTING;
MALES WITH LOTS OF MATING OPPORTUNITIES SHOULD DEVOTE MORE ENERGY
TO MATING;
These are ALTERNATE CONDITIONAL STRATEGIES; i.e., they are if-then rules:
If I am attractive, I should pursue a mating strategy; If I am not attractive,
I should pursue a parenting strategy.
E.G., ATTRACTIVE MALE ZEBRA FINCHES ENGAGE IN LITTLE PARENTING EFFORT.
FEMALES WHO MATE WITH THEM PAY A PREMIUM: THEY MUST ENGAGE IN MORE PARENTING
EFFORT
ALTERNATE CONDITIONAL STRATEGIES
1. CHOICE OF TACTICS CUED BY SPECIFIC ENVIRONMENTAL FEATURES;
E.G, IF ATTRACTIVE, INCREASE MATING EFFORT.
IF UNATTRACTIVE, INCREASE PARENTING EFFORT
2. ALTERNATE STRATEGIES ARE GENETIC UNIVERSALS (SPECIES-TYPICAL, WITHIN SEX)
3. ALTERNATE STRATEGIES LEAD TO GREATER FITNESS THAN STRATEGIES
THAT DO NOT TAKE ACCOUNT OF CONTEXTUAL VARIATION.
E.G., THE ALTERNATE STRATEGY 'IF ATTRACTIVE SEEK LARGE
NUMBERS OF FEMALES' WOULD HAVE TO LEAD TO HIGHER FITNESS THAN 'ALWAYS
SEEK LARGE NUMBERS OF FEMALES'
THERE IS MEAN DIFFERENCE BETWEEN MEN AND WOMEN ON DESIRE FOR SEX WITHOUT COMMITMENT, BUT DISTRIBUTIONS OF MEN AND WOMEN OVERLAP. ABOUT 30% OF MEN EXPRESS LESS FAVORABLE ATTITUDES TOWARD UNCOMMITTED SEX THAN THE MEDIAN FOR WOMEN.
THIS SUPPORTS THE ALTERNATE STRATEGY THEORY.
BEST STRATEGY FOR 'TYPICAL MAN' MAY BE TO INVEST IN OFFSPRING OF SINGLE
MATE. ANALOGY: IF THE BEST JOB IS TO BE A BRAIN SURGEON, BECOMING ONE IS
NOT A GOOD STRATEGY FOR MOST MEN.
GOOD GENES SEXUAL SELECTION
LOW FLUCTUATING ASSYMETRY IS THE BEST MARKER OF GOOD GENES
FA = DEGREE OF DEVIATION FROM PERFECT SYMMETRY ON BILATERAL FEATURES.
FA RESULTS FROM GENETIC (e. g., MUTATIONS) OR ENVIRONMENTAL DISRUPTIONS (e. g., EXPOSURE TO PATHOGENS); ASSOCIATED WITH LOWER FUCUNDITY, SLOWER GROWTH, POORER SURVIVAL
HYPOTHESES: MEN WITH LOW FA WILL SEEK EXTRA-PAIR MATINGS;
a.) MEN WITH HIGH FA WILL INVEST IN ONE FEMALE
b.) WOMEN WILL PREFER LOW FA MEN AS SHORT-TERM OR EXTRA-PAIR
MATES
c.) WOMEN WITH ACCESS TO RESOURCES WILL VALUE GOOD GENES
RATHER THAN PATERNAL INVESTMENT (CONTRADICTS BUSS; DATA
ARE MIXED)
FINDINGS:
LOW FA MEN 1.) HAVE MORE LIFETIME SEXUAL PARTNERS
2.) HAVE MORE EXTRA-PAIR SEX
3.) ARE CHOSEN BY WOMEN AS EXTRA-PAIR PARTNERS AND
FOR SHORT-TERM SEX BY 'SEXUALLY UNRESTRICTED
WOMEN'
FREQUENCY OF FEMALE ORGASM NEGATIVELY CORRELATED WITH FA OF MALE (SELF-REPORT).
FEMALES PREFER LOW FA MEN GREATEST DURING OVULATION. (BASED ON SWEAT PREFERENCES)
FA ASSOCIATED WITH 1.) PHYSICAL ATTRACTIVENESS,
2.) BODY
MASS
3.) PHYSICALITY
(MUSCLE MASS, VIGOR)
4.) SOCIAL
DOMINANCE
5.) DIRECT
COMPETITIVE TACTICS e. g., FIGHTING, DEROGATING
COMPETITORS
6.) INTELLIGENCE
LOW FA MEN INVEST LESS IN RELATIONSHIPS: LESS NURTURANT,
LESS HONEST, MORE PHYSICALLY PROTECTIVE
REGIONAL ENVIRONMENTAL DIFFERENCES:
TROPICAL AREAS:
1. PATHOGEN PREVALENCE;
2. SELECTION FOR LOW FA
3. LACK OF MALE INVESTMENT
4. MALES DEVOTE MORE EFFORT
TO MATING
5. FEMALES DON'T NEED MALES'
INVESTMENT
6. FEMALES LOOK FOR GOOD
GENES (LOW FA)
FA is quite important
NORTHERN AREAS
1. PATHOGENS NOT PREVALENT
2. LESS SELECTION FOR LOW
FA
3. MALE INVESTMENT NEEDED
4. MALES DEVOTE MORE EFFORT
TO PARENTING
5. FEMALES LOOK FOR MALES
WHO ARE GOOD PARENTS
FA less important
Genghis Khan a Prolific Lover, DNA Data Implies
http://news.nationalgeographic.com/news/2003/02/0214_030214_genghis.html
Hillary Mayell for National Geographic News
February 14, 2003
Genghis Khan, the fearsome Mongolian warrior of the 13th century, may have done more than rule the largest empire in the world; according to a recently published genetic study, he may have helped populate it too.
An international group of geneticists studying Y-chromosome data have found that nearly 8 percent of the men living in the region of the former Mongol empire carry y-chromosomes that are nearly identical. That translates to 0.5 percent of the male population in the world, or roughly 16 million descendants living today.
The spread of the chromosome could be the result of natural selection, in which an extremely fit individual manages to pass on some sort of biological advantage. The authors think this scenario is unlikely. They suggest that the unique set of circumstances surrounding the establishment of the Mongol empire led to the spread.
By analyzing DNA from people in all regions of the world, geneticist Spencer Wells has concluded that all humans alive today are descended from a single man who lived in Africa around 60,000 years ago. His research was showcased in the television documentary Journey of Man, which aired recently in the United States on PBS and throughout the rest of the world on the [25]National Geographic Channel. Spencer Wells' research is funded in part by the National Geographic Society.
"This is a clear example that culture plays a very big role in patterns of genetic variation and diversity in human populations," said geneticist Spencer Wells, one of the 23 co-authors of the paper. "It's the first documented case when human culture has caused a single genetic lineage to increase to such an enormous extent in just a few hundred years."
Legacy of Genghis Khan
To have such a startling impact on a population required a special set of circumstances, all of which are met by Genghis Khan and his male relatives, the authors note in the study published in the American Journal of Human Genetics.
Khan's empire at the time of his death extended across Asia, from the Pacific Ocean to the Caspian Sea. His military conquests were frequently characterized by the wholesale slaughter of the vanquished. His descendants extended the empire and maintained power in the region for several hundred years, in civilizations in which harems and concubines were the norm. And the males were markedly prolific.
Khan's eldest son, Tushi, is reported to have had 40 sons. Documents written during or just after Khan's reign say that after a conquest, looting, pillaging, and rape were the spoils of war for all soldiers, but that Khan got first pick of the beautiful women. His grandson, Kubilai Khan, who established the Yuan Dynasty in China, had 22 legitimate sons, and was reported to have added 30 virgins to his harem each year.
"The historically documented events accompanying the establishment of the Mongol empire would have contributed directly to the spread of this lineage," the authors conclude.
Tracking the Y-Chromosome
The study looked at blood samples collected over a period of ten years from more than 40 populations living in and around the former Mongol empire.
Geneticists use the Y-chromosome in population studies such as this because it doesn't recombine as other parts of the genome do. When it comes to eye color, or height, or resistance or susceptibility to particular diseases, each parent contributes half of a child's DNA, which join together to form a new genetic combination.
The Y-chromosome is passed on as a chunk of DNA from father to son, basically unchanged through generations except for random mutations.
These random mutations, which happen naturally and are usually harmless, are called markers. Once the markers have been identified, geneticists can go back in time and trace them to the point at which they first occurred, defining a unique lineage of descent.
In this particular instance, the lineage originated 1,000 years ago. The authors aren't saying that the genetic mutations defining the lineage originated with Khan, who was born around 1162; they are more likely to have been passed on to him by a great great grandfather.
The lineage was found in only one population outside of the former Mongolian empire, in Pakistan.
"The Hazaras [of Pakistan] gave us our first clue to the connection with Genghis Khan," said Wells. "They have a long oral tradition that says they're his direct descendants."
Of course, the connection to Genghis Khan will never be a certainty unless his grave is found and his DNA could be extracted. Until then, geneticists will continue to seek out isolated populations in the hope of unraveling the mysteries of geographic origin and relatedness told by our genes.
References
25. http://www.nationalgeographic.com/channel/intl/
