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Evolution of the distinction of gender

Discussion of everything related to the Theory of Evolution.

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Evolution of the distinction of gender

Postby ragav.payne » Sat Mar 01, 2008 2:59 pm

For the past few weeks, I've been wondering about why there would be an evolution of gender distinction in animals in the first place. Agreed; there is no "why" to evolution...but "how" did it come about? I just can't imagine a point where hermaphrodite species split into sub-species that are mutually dependent for reproduction.

Along with this question came the following:-

Is the clitoris and labia underdeveloped penis and scrotum respectively?
Are men's nipples vestigial remains from our hermaphrodite ancestors?
By golly, are men malformed versions of women? vice versa?

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Postby canalon » Sat Mar 01, 2008 7:20 pm

The advantage and inconvenent of sexual reproduction have been discussed in many books. A very good book on the subject is Matt Ridley's "the red queen."
The main arguments are:
- sexual reproduction allow a better mix of genes.
- Once it was implemented, it is quite hard to get rid of it.

And there never was human hermaphrodites, because even the most ancestral mammal already reproduced sexually, and in fact most memgers of the animal kingdom. So there never were such things as asexual hermaphroditic ancestral humans, monkeys, shark, squid or anything. But devlopment use the same blueprint to create male and female, that is why you can see some sort of vestigial organs in one sex that are well developed in the other sex.
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Re: Evolution of the distinction of gender

Postby Darby » Mon Mar 03, 2008 1:16 am

The basic difference in gender is purely in the gametes (not all sexual reproducers have genders, but most do), and to have one specialized for holding food for the offspring and the other specialized to get to the first one is the underlying cause of all of the other differences.
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Postby bionecrology » Mon Apr 07, 2008 6:08 pm

Well, reproduction requires energy, and can make an organism vulnerable. Thus, reproduction can be hazardous to survival; for instance, studies of whales and sharks. Having a slightly less vulnerable gender could be advantagious to survival, and perhaps we are the living proof. Some books on the subject have overlooked environmental factors for finding the first instance of sex, but what do you want for a few hundred years of scientific study on a meger budget, and religion breathing down your neck?
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Re: Evolution of the distinction of gender

Postby Anaximenes » Sun Apr 27, 2008 10:37 pm

Sexual dimorphism in some species also seems to have important results in terms of encouraging pro-survival activities and behaviours. For example, in insect populations like bees and ants, the phenomenon of gender allows members of the group to assume radically different roles - a kind of "division of labour" which increases the efficiency of the group - and hence is an evolutionary advantage.

To a lesser extent, you could argue that this manifested itself somewhat in birds, reptiles and social mammals as well, such as baboons and dolphins, where gender differences create the groundwork for the complex social hierarchy which favours group survival.

(For the record, I'm just throwing down ideas, I'm not a proper biologist)
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Postby alextemplet » Tue Apr 29, 2008 6:00 pm

Very good points. One could almost wonder what implications these "instinctive roles for each gender" could have for the modern feminist movement.
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Postby Darby » Tue Apr 29, 2008 7:00 pm

People aren't very good at working from instincts - one of our strongest adaptations is our ability to ignore our weak instincts and alter our behavior for new situations.
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Postby alextemplet » Wed Apr 30, 2008 3:03 pm

To a large extent that is true of most vertebrate species. What we often think of as "genetically programmed instincts" are in fact the product of conditioning by experience. It's the age-old nature vs. nurture debate.
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Re:

Postby Anaximenes » Thu May 01, 2008 8:14 pm

alextemplet wrote:To a large extent that is true of most vertebrate species. What we often think of as "genetically programmed instincts" are in fact the product of conditioning by experience. It's the age-old nature vs. nurture debate.


Partly true, but some particular examples of physical sexual dimorphism do come to mind, which can only be caused by genetics. Environmental conditioning does not, for example, cause male peacocks to have and display plumage for sexual conquest, or for female peacocks to be wooed by said plumage.
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Postby alextemplet » Fri May 02, 2008 12:00 am

Although it is true that nurture does not cause a peacock to have a larger plume, it may have at least something to do with the female finding that plume attractive. For example, humans are almost automatically genetically programmed to find the opposite sex attractive, yet which particular features we find most attractive can be greatly influenced by culture. Consider, for example, the western world's obsession with toothpick-sized women; just a few centuries ago this would have been considered a very unattractive sign of ill health. Latin-American cultures, for example, prefer women who are more solidly built and thus better suited to the harsh working lives of those countries. I think most "instincts" are therefore a combination of both nature and nurture.
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