Chapter 4.pdf

8 Pages
Unlock Document

Western University
Psychology 3229A/B
Scott Mac Dougall- Shackleton

Chapter 4: The Evolution of Human Mate Choice Testing the Claims of Evolutionary Psychologists • Two of the main claims made by evolutionary psychologists are that there is a human nature and that ecological and social pressures of the past were responsible for the evolution of that nature • People who made poor mat choices int eh ancient past were less likely to pass on their genes than those who made good choices • Sexual selection should, therefore, promote ‘good’mating choice strategies • We explore the relationship between sexual selection, mate choice and human behavior one way by comparing ourselves with out primate relatives that shared a common ancestry with us • Comparing different species in order to add to our knowledge of anatomy, physiology or behavior is called the comparative method • When behavior patterns differ between closely related species then it might be argued that these differences can be traced back to differing ecological pressures • Where behavioral patterns are similar it may suggest that the responses are ancient and might be traced back to a common ancestor • Asecond way in which we can study the evolution of human mate choice is by examining the degree to which such responses are common to separate human cultures Origins of Human Mate Choice: The Social Behavior of Our Relatives • Two main species of primates have been used as models for human behavior: chimpanzees and baboons • Chimpanzees • Chimpanzees share over 98% of their genes with humans and current thinking suggests we shared a common ancestor with them some time between 6-8 million years ago • Highly social, group-living individuals • Males form the permanent core of their society, while females generally leave to join another troop upon reaching sexual maturity • Dominance hierarchy • Despite being largely frugivorous chimps do sometimes engage in group hunting of small animals - an activity which is largely the preserve of males • If rank order and hunting prowess are useful indicators of good genes why do they mate with a number of males? • One answer may be to confuse and hence elicit aid from a number of potential fathers • Baboons • Share 94% of genes • They may well have shared similar ecological pressures • Baboon troops vary around 40-80 individuals • Their diet is largely vegetarian • After human, baboons are the most carnivorous of all primates • Hunting is largely a male preserve and, although baboons are not renowned for sharing their kills they may share with potential mates • Males and females form parallel dominance hierarchies with dominant males having first access to oestrous females Chapter 4: The Evolution of Human Mate Choice • Dominant male baboons of a number of species attempt to limit the access of other males by forming consort relationships with females in oestrus Reconstructing Human Behavioral Evolution • Are Humans Different? • There are three related areas that we can consider - diet, social behavior and reproductive strategies • Meat-eatingAncestors • For at least the last 2 million years, our ancestors lived in small troops of hunter-gatherers on the open savannah • We were likely to have exploited a range of plant foods • Evidence that meat has been of long-standing importance in our diet • Our relatively long small intestine and cutting edges of our incisors, canines, and premolars all suggest that meat played a prominent role during out savannah-dwelling ancestry • VitaminsAand B12 are those which we are no longer able to synthesize form a plant-based diet • Today these vital nutrients are only available to use through animal products • The Provisioning Hypothesis • One area where human differ from chimps and baboon lies in the lack of oestrous swelling in females • Tooby and DeVore are most conducive to what has been called the provisioning hypothesis • There are debates as to whether our ancestors and those of baboons left the rainforest in order to exploit the open grasslands or whether we were elbowed out of the diminishing rain-forests • One suggestion is that when our early human-like ancestors or hominids, left the shelter of the rain-forests and began to live on the open savannah they, unlike baboons made use of their primate features to take serious advantage of the animal life that lived there • This change to open savannah hunting may have had important consequences for both sexes • Males of modern day hunter-gatherer societies who are prolific hunters are the ones who are seen as the most attractive by the women of such bands • If women preferred males that were most able to provide them with meat then we could see immediately that, over evolutionary time, sexual selection would increase hunting prowess in males since females would be choosing their mates on such a basis • Why Only Men? • Women also have large brains, hands that can grip with precision and good stereoscopic vision • The problem for women as hunters is that control over the reproductive cycle is a recent human invention • Hunting was a less likely option since for most of their adult lives they would either be lactating or pregnant • For this reason it has been argued that this hunting/gathering sexual division of labor is likely to be ancient Chapter 4: The Evolution of Human Mate Choice • Anumber of researchers have argues that a shift towards hunting by men may have had a knock-on effect on the oestrus cycle of women • Women bear a child-rearing burden that would not be entirely compatible with big-game hunting • Perhaps while male hominids took advantage of the game available on the savannah, female hominids took advantage of the males • Perhaps by forming a long-term sexual relationship with a good hunter, a woman and her offspring would benefit from the food provided in return • Note that according to this argument the long-term pair bonds formed would have benefited both male and female partners • Why do Men Help Out? • The fossil record shows that this change to bipedalism did happen early • This change to habitual bipedalism led to a narrowing of the pelvic girdle • This, in turn, meant that a large brained baby could only be passed through the pelvis at a highly immature stage • This means that they require almost constant attention for a considerable period compared with any other animal • Females dealt with this problem, so the argument goes, by forming long-lasting air bond with male partners who were prepared to help provide for the offspring • Technically this is called high male parental investment • Cryptic Oestrus • Alexander and Noonan have suggested that by concealing their period of estrus (which they call ‘cryptic oestrus’) women may have made men attentive to them continually, since only in this way would males be able to ensure that they father a partner’s offspring • Badcock suggests that rather than never appearing to be in oestrus, women appear to be permanently in that state • Human females, in contrast to all other primates, have permanently swollen breasts during their fertile years • In this way human females may be providing a false oestrus signal and are therefore permanently sexually attractive to men • Thus the development of oestrus may have come about via sexual selection • This constant female sexual attraction may well be a unique human feature and it may have led, in turn, to a unique long-lasting pair bond • Forming a pair would also have required a degree of psychological re-plumbing in both sexes • Science or Speculation? • Some readers might have found the arguments based around the provisioning hypothesis somewhat speculative • At present the provisioning hypothesis does appear to explain a large number of features that set us apart form other primates • In the future, however, new evidence or other arguments could arise which might weaken it Chapter 4: The Evolution of Human Mate Choice • When dealing with purely anatomical features, however, we can be a little more confident in making use of the comparative method since physical features are ultimately there to provide support for behavior and may be quantified more accurately than behavior Sexual Dimorphism and Mating Systems • Darwin called the degree to which the sexes differ in physical characteristics sexual dimorphism • Human males are about 20% bigger than their female counterparts • Current theory suggests that the greater the increase in male size relative to females the greater the competition between males for access to groups of females • Specie is in which the largest and strongest males monopolize groups of females are said to be polygynous • Hence polygyny is a form of polygamy where one male has access to a number of females but each female is normally limited to one male • One female monopolizes a umber of males is called polyandry • In monogamous species where a lasting pair bond is formed sexual dimorphism is likely to be low since, once paired up, males are no longer in competition for further mates • Mating system vary greatly between human cultures Human Mating Strategies • Buss and his collaborators present men and women with a list of eighteen characteristics that they might find desirable in a serious long-term partner • The range of different cultures chosen is a least important as the actual members samples • Uncovering difference between the relative ratings of various attributes both within and between the sexes in a single culture is clearly of interest • It tells you about that culture • However, by using only one culture we are unable to determine to what extent such a pattern is culture specific • In large-scale cross-cultural studies universal similarities might be taken as evidence of a species-specific response Long-term Mate Choice Preferences • Preferences for Financial Resources, Industriousness and Social Status • Women rate social status, industriousness and financial prospects highly in potential male partners and that men regard such features as of lesser importance in women • Men of particularly high occupational status are able to attract and marry particularly attractive women • This supports the notion that, since ancestral females invested so highly in their offspring, they would have benefited greatly from choosing mates that were able to provide for them and their offspring • Although women in all cultures favor these characteristics more highly than men do, the degree of differe
More Less

Related notes for Psychology 3229A/B

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.