Dichotomous Male Reproductive Dichotomous Male Reproductive Strategies in a Polygynous Human Strategies in a Polygynous Human

Society: Mating versus Parental Society: Mating versus Parental EffortEffort

Kevin CurryKevin CurryYolanda MejiaYolanda MejiaAnavely RodriguezAnavely Rodriguez

IntroductionIntroductionLife history theory: idea that organisms Life history theory: idea that organisms

face the decision regarding the trade-off face the decision regarding the trade-off between quality and quantity of offspring.between quality and quantity of offspring.Males: generally emphasize offspring quantityMales: generally emphasize offspring quantityFemales: generally emphasize offspring Females: generally emphasize offspring

qualityqualityThis creates conflict of interest This creates conflict of interest

Summary of ArticleSummary of Article Goal of paper: to examine the effect of Goal of paper: to examine the effect of

wealth on the decision of male mating wealth on the decision of male mating versus parental effort using offspring versus parental effort using offspring survivorship as a measure of parental survivorship as a measure of parental investment. investment.

Hypothesis:Hypothesis:1: 1: a. Wealthy males will attract and gain a. Wealthy males will attract and gain

more marriage partners.more marriage partners.b. have higher completed fertilityb. have higher completed fertilityc. have more surviving offspringc. have more surviving offspringd. have higher reproductive careers d. have higher reproductive careers than poor males than poor males

2: a. Poor males will have more offspring 2: a. Poor males will have more offspring per wife than wealthy malesper wife than wealthy malesb. have more surviving offspring per b. have more surviving offspring per wife than wealthy maleswife than wealthy males

MethodsMethodsSample of 90 males, their wives and Sample of 90 males, their wives and

offspring offspring Household: a married man with one or more wives Household: a married man with one or more wives

and their respective offspring. and their respective offspring. Male fertility: all offspring recorded as sired by the Male fertility: all offspring recorded as sired by the

male head of household.male head of household.Male’s reproductive career: calculated from the Male’s reproductive career: calculated from the

time between the first recorded and the last time between the first recorded and the last recorded birth of his offspringrecorded birth of his offspring

Offspring survivorship: survivorship to 15 years of Offspring survivorship: survivorship to 15 years of ageage

ResultsResults

– Wealthy males had significantly more offspring survive to 15 years old than poor males

-When the likelihood of obtaining mates is slim because of lack of resources, males may be maximizing a mating strategy through parental effort.

Results cont.Results cont. Wealthy males have significantly more wives Wealthy males have significantly more wives

than poor males (consistent with Ia.) and than poor males (consistent with Ia.) and therefore Wealthy males sired significantly therefore Wealthy males sired significantly more offspring per reproductive year than more offspring per reproductive year than poor males (prediction Ib.)poor males (prediction Ib.)

Wealthy males had longer reproductive Wealthy males had longer reproductive careers than poor ones (prediction Id.)careers than poor ones (prediction Id.)

DiscussionDiscussionConsistent with Darwinian Theory Consistent with Darwinian Theory Monogamy is a result of unsuccessful Monogamy is a result of unsuccessful

mating strategy mating strategy Monogamy and Parental Care are Monogamy and Parental Care are

correlatedcorrelated

Critique of ArticleCritique of Article Sample: 90 males and their wives in Utah Sample: 90 males and their wives in Utah

territory in the 19th century. territory in the 19th century. The sample is too small and therefore is not a proper The sample is too small and therefore is not a proper

representation of the entire population.representation of the entire population. Men were mormons who entered polygynous Men were mormons who entered polygynous

marriages. marriages. Using only mormons is not representative of the entire Using only mormons is not representative of the entire

male population. male population. 1850 1860 and 1870 US census.1850 1860 and 1870 US census.

This is not representative of the most recent census This is not representative of the most recent census therefore it is difficult to relate this sample to present therefore it is difficult to relate this sample to present day population. day population.

Critique cont. Critique cont. The study measured male wealth as quality The study measured male wealth as quality

but failed to take into account other male but failed to take into account other male qualities that can make a difference in parental qualities that can make a difference in parental investment such as:investment such as: Male healthMale health Special skills the male may possesSpecial skills the male may posses Social statusSocial status Number of kinNumber of kin Or any combination of the above mentionedOr any combination of the above mentionedThis could have explained inter and intrapopulation This could have explained inter and intrapopulation

male reproductive strategies.male reproductive strategies.

Critique cont.Critique cont. This article has shown that monogamy in This article has shown that monogamy in

paternal investment helps increase paternal investment helps increase survivorship of offspring, however in class survivorship of offspring, however in class we have discussed that it is not in a male’s we have discussed that it is not in a male’s best interest to be monogamous. best interest to be monogamous.

QuizQuiz 1. Parental effort was measured in the study by looking at:1. Parental effort was measured in the study by looking at: a. lifetime reproductive success of parentsa. lifetime reproductive success of parents b. genetic variabilityb. genetic variability c. survivorship of offspringc. survivorship of offspring 2. The study found that monogamy is closely associated with:2. The study found that monogamy is closely associated with: a. the occurrence of genetic mutationa. the occurrence of genetic mutation b. parental careb. parental care c. fitness of offspringc. fitness of offspring 3. Survivorship of offspring was measured up to:3. Survivorship of offspring was measured up to: a. age 18a. age 18 b. age 15b. age 15 c. age 21c. age 21 True/FalseTrue/False 4. Male fertility was defined in the article as all offspring recorded as sired by the male 4. Male fertility was defined in the article as all offspring recorded as sired by the male

head of household.head of household. 5. Males generally emphasize offspring quality rather than quantity.5. Males generally emphasize offspring quality rather than quantity. 6. Wealthy males had shorter reproductive careers than poor males. 6. Wealthy males had shorter reproductive careers than poor males.

Class DiscussionClass Discussion Parenting investment as a mating strategy. Parenting investment as a mating strategy.

Male baboons that show affection to their offspring Male baboons that show affection to their offspring are more likely to mate more with their mother. are more likely to mate more with their mother.

High quality males resort to mating and escape High quality males resort to mating and escape parenting where as low quality males resort to parenting parenting where as low quality males resort to parenting skills and take care of the few offspring they have so that skills and take care of the few offspring they have so that their offspring survive. their offspring survive.

This study has shown that high quality males have more This study has shown that high quality males have more offspring pass away than do low quality males. offspring pass away than do low quality males. Shouldn’t males with more resources have more Shouldn’t males with more resources have more

children surviving? Which theory do you agree most children surviving? Which theory do you agree most with?with?

Questions?Questions?

Thank youThank you