3. Evolution of sex differences
[Note: Alex Cooke appears to be responding to Judy Chatwin, but Judy's
original comments don't seem to have been posted. Weere they posted to
Alex? -- SH.]
>>For the present argument, sexual selection is broadly
>>defined to include
>>characteristics that directly influence the outcome
>>such as physical strength, as well as less direct
>>influences on the outcome
>>of any such competition.
jc?> Does this mean that all sex differences can be accounted for
jc?> by the desire for males to compete against other males in
jc?> order to win a mate?
According to the article - yes. I believe this to be true,
although it may not always be conscious, i.e answering a
maths problem first, is probably not the best technique for
aquiring a mate. The element of competition is certainly present
but I do not believe it is always to win a mate. This behaviour
is seen in young children, i.e. 4 year old boys who often don't
even want to sit next to girls let alone find a mate!
>>Trivers (1972) argued that sex differences in the level of
>>investment in offspring "governs the operation of sexual
>>selection" (p. 141),
>>and, as such, is the ultimate cause of any associated sex
>>The higher-investing sex, in contrast, is expected to be
>>discriminating in terms of choosing sexual partners, with
>>focusing on a potential partner's physical characteristics
>>or behaviors that
>>might benefit future offspring.
jc?> Does this not reflect the fact that women are far more
jc?> limited in the number
jc?> of off-spring they can produce and therefore have less room
jc?> for error?
The answer must be yes. there is no point in producing too many
offspring, if you cannot look after them. There is little point in
producing many weak offspring, if there is a potential for strong
In the animal kingdom, of which we still belong, and therefore I will
say with the exception of 'first world humans' where food is
a comodity, if there are two offspring, the mother will ALWAYS
feed the strongest first, while the weak one will often die. To
increase the chance of survival of the mothers genes, she wants only
to mate with the fittest male, however if the fittest male is not
an option for what ever reason, she will try to mate with another
male, since in this way the possibility of her genes being passed on
is greater than if she does not mate at all.
For the male it is a different story, since he often takes less
or even no care of the offspring. Due to the high motality rate of
offspring it is in the intrest of the male to mate as many times as
possible, with as many females as possible, to increase his chance of
passing on his genes. The passing on of the genes is more important
for the male, since the males mortality rate is higher than that of
>>First, sex hormones are likely to be an important proximate
>>mechanism for the
>>development of any sex differences associated with sexual
>>Second, sex differences in social behaviors and cognitive
>>abilities that are
>>relatively insensitive to historical and cultural changes
>>also need to be
>>considered as potentially related to sexual selection.
>>Third, it is possible that sex differences in early play
>>later sex differences in cognitive abilities (Serbin &
>>Finally, the associated social and cognitive skills should
>>plausible function related to reproductive success.
jc?> When looking at sex differences in social and cognitive
jc?> styles, you need to
jc?> consider the influence of sex hormones, which behaviours and
jc?> abilities have
jc?> not been affected by history and cultures, how early
jc?> developmental behaviour
jc?> can affect later ability and their relevance to successful
Good point well made. Just to add that play could be highly
instumental in mathematical abilities, such as those mentioned in
original text, i.e males have better judgement of velocity etc. In
the case of human children in the present day, this could reflect on
boys playing computer games etc. far more than girls. Hence their
exposure to seeing object moving and rotating should be higher than
for non computer playing children.
>>Human males are verbally and physically more aggressive
>>than females across
>>cultures (Eibl- Eibesfeldt 1989; Rohner 1976).
>>Moreover, Susman et al. (1987) found that during
>>adolescence, adrenal and
>>gonadal hormones were related to aggression and delinquency
>>in human males
>>but not females.
jc?> Does this increased aggression relate to increased
jc?> competitiveness in the
jc?> If this is the case why does it not affect all academic
jc?> achievement rather than emphasize mathematical ability?
Maths is an object subject as opposed to a social subject, i.e.
languages. As was said in the text, boys are cross culturally more
object orientated than girls who are more socially orientated, as can
be seen in playground behaviour.
>>..sex differences in competitive and aggressive behavior
>>are often very large
>>under conditions that represent a threat to the male's
>>status, or might
>>directly influence reproduction, e.g., sexual jealousy
>>(Daly & Wilson 1988;
>>Wilson & Daly 1985).
jc?> Beware generalizations, the author seems to be forgetting
jc?> the male individuals
jc?> who do not display these characteristics. If aggression and
jc?> are such dominant features when why hasn't natural selection
jc?> led to these
jc?> characteristics being displayed in all males?
We must remember that humans have created Gods, morals and laws.
These thus make humans repress natural behaviours. Human
socialisation also depends on vocal communications and technologies,
and medecines, which those who we have evolved from did not have. I
feel that natural selection in humans is not so important as it used
to be, nor as it is to the remainder of the animal kingdom.
>>During the preschool years and into adulthood, girls'
>>social styles reflect,
>>relative to boys' styles, a greater concern for
>>more cooperation, and a greater concern for the feelings
>>of other group
>>members (usually other girls; Buhrmester & Furman 1987;
>>Maccoby 1988; 1990).
>>..males appear to be relatively more object oriented, and
>>females more people
>>oriented (McGuinness 1993; Thorndike 1911).
>>This is not to say that this pattern necessarily supports a
>>mechanism associated with sexual selection, but rather
>>suggests that parental
>>socialization is not likely to be the sole cause of the
>>sex difference in
>>object versus people preferences.
jc?> This would seem to be an important factor in explaining the
jc?> differences in
jc?> mathematical abilities.
I have spoken of this previously.
>>Nevertheless, it is more likely that the object preferences
>>of boys reflect a
>>bias toward learning about the physical, as opposed to the
jc?> I agree, but remember there are exceptions.
Again these are probably due to man kinds departure from natural
>>..it has been frequently argued that the male advantage in
>>certain areas of
>>mathematics (e.g., problem solving) is related to a male
>>advantage in spatial
>>abilities (e.g., Benbow 1988; McGee 1979).
>>..in a meta-analysis of sex differences on the Mental
>>Rotation Test (MRT;
>>Vandenberg & Kuse 1978), a measure of the ability to
>>mentally rotate 3-
>>dimensional geometric figures, Masters and Sanders found a
>>advantage (3/4 to 1 1/4 standard deviations) in 14 of the
jc?> Need to consider the cognitive abilities used for this test
jc?> and relate them to
jc?> other mathematical abilities.
Surely, this relates to the object orientatation of males. Exposure
to rotating objects, such as toys, and especially in the visual
computer rotations of objects on a screen while playing computer
games will enhance and stimulate ones cognitive abilities.
>>Furthermore, "there is now substantial evidence that
>>cognitive patterns may
>>vary with phases of the menstrual cycle in normally cycling
>>women and with
>>seasonal variations in androgens in men" (Kimura & Hampson
>>1994; p. 57).
jc?> It seems that hormones cannot be ignored when considering
jc?> any sort of sex
jc?> differences in cognitive abilities.
>>The point is---if males with superior spatial abilities
>>hunting and, for example, group migration or warfare) had
>>even a slight
>>reproductive advantage over their low-ability peers, then
>>a sex difference,
>>favoring males, in certain spatial abilities (e.g., those
>>processing of 3- dimensional information) would have
>>emerged over the course
>>of human evolution.
jc?> But what about those males who do not display such superior
jc?> ability - why are
jc?> they here at all?
We could not live in a world full of ultimate ability, in the way
that we live now. Imagine if we had an army full of majors, no one
would drive the tanks! If we still lived by the rules of natural
selection maybe 'they' would not be here at all. We have chosen to
deviate away from natural selection, and the result is weak
organisms, supported by technologies to make them stronger.
>>For complex spatial measures, the male advantage is found
>>periods and cultures, is influenced by prenatal exposure to
>>sex hormones, and
>>fluctuates with circulating levels of sex hormones.
>>The proximate mechanisms governing the emergence of these
>>include sex hormones and a biological bias in the
>>of boys and girls, a bias that is also likely to be
jc?> As usual - a bit of both!
Exactly! it's time psychologists put there heads together and admit
that it is 'a bit of both'. Why is it always nature vs nurture? If
both sides swallowed a bit of pride, maybe we could start to advance,
as a science a little bit faster.
>>..the position that sexual selection might be related to
>>the tendency of
>>males to show more variability in some cognitive domains
>>than females is
>>relevant to the issue of sex differences in mathematics
>>Feingold 1992; Thorndike 1911).
>>Greater variability in reproductive strategies would
>>presumably result in
>>greater variability in any associated social or cognitive
>>..there are more males than females at the high and low
>>ends of many ability
jc?> It is unclear just how great this variability is and
jc?> therefore how relevant it
jc?> is. It is possibly that social factors could explain it.
I agree the article does not make it clear, but from past experience
in the classroom, I feel the point is a valid one. I will not attempt
to try and explain this phenomenom.
>>.. not only are males more variable in many cognitive
>>abilities, they are
>>also at much greater risk than females for an array of
>>other physiological disorders (e.g., Gualtieri & Hicks
>>1985; Stillion 1985).
>.Sex hormones have been implicated as one source of these
>>Such deleterious effects of male hormones might explain the
>>greater number of
>>males than females at the low end of many ability
>>distributions, but does not
>>explain the greater number of males at the high end of
jc?> It has also been suggested that males are more sensitive to
jc?> the environment,
jc?> poor environment = negative impact, good environment =
jc?> positive impact - this
jc?> view may explain the greater variability in the male
A possible explanation, but I cannot quite link favourability of the
environment to sex hormones!
>>The greater variability in the reproductive success of
>>males, relative to
>>females, might have created pressures for males who were
>>not successful in
>>modal forms of intramale competition to develop
>>strategies (Le Boeuf 1974).
>>It seems that there are many different routes to high
>>status for males.
>>Presumably, different routes to high status would have led
>>patterns of cognitive abilities being selected for in
>>males who used
>>different reproductive strategies.
jc?> These factors may also have led to greater variability
jc?> within the males,
jc?> thereby offering an explanation for the wider distribution.
This is a good possibility. Perhaps it is possible that males
who are stronger, more athletic, i.e fitter, in the natural selection
sense, feel they do not need other educational abilities to increase
their 'fittness', while those who do not possess such abilities, feel
they should excell in an educational ability to increase their
fittness. (not sure about that now that i've written it! doesn't
explain those who are good at both, i.e. fit in both ways)
>>.. sexual selection and its consequences might be one
>>from which the issue of the sex difference in intrasexual
>>variability can be
>>addressed. Second, sex differences in the distributions of
>>abilities has important implications for interpreting mean
>>sex differences in
>>mathematical abilities, because mathematics is a domain
>>where a consistent
>>sex difference in variability is found; males are more
>>variable than females
>>(e.g., Feingold 1992).
jc?> The need to understand variability in sex differences is as
jc?> important as
jc?> understanding the mean sex differences because of the
jc?> variation in the number
jc?> of males and females at each end of the ability
jc?> distributions. There is also
jc?> a need to relate these differences to mathematical abilities
jc?> because of the
jc?> consistent sex difference in variability found in this area.
Couldn't have put it better myself
This archive was generated by hypermail 2b30 : Tue Feb 13 2001 - 16:23:19 GMT