What characrerises reproductively successful men? Or, to put it another way, what qualities do women seek in a mate? Women tend to prefer dominant men of high status with lots of money, and there is little reason to believe that their ancestors differed. For much of human history male status came from being a skilled hunter and warrior and from the ability to influence others through muscle or wit. This history has left men more disposed than women to strive for status and engage in the risky, competitive and sometimes aggressive behaviour often required to do a successful startup. Women with a taste for winners would likely be in a position to pass their preference on to more children than would women with a penchant for failures.
Women would not ordinarily enhance their reproductive success through direct competition and risk-taking. Indeed, it would promise little reproductive payoff and could be a very dicey strategy because a bad outcome would imperil a woman's future reproduction and the well-being of existing children. Instead, women, to a far greater extent than men, have enhanced reproductive success by looking after their children as they grow up, resulting in stronger bonds between mother and child than between father and child.
This explanation also hints at the fact that women would make good CEO's of large corporations where security is more important than risk taking.
Note: this isn't in in any way meant as a degradation of women - merely a possible explanation of the cause.
Unfortunately, your explanation does not go the whole way.
Consider the evolution of biological genes:
a) Men and women share mostly the same genes (the y chromosome is a desolate wasteland), and there are few (if any) known mechanisms by which gene merging is different for male and female humans.
b) Dominant, decisive, intelligent, women are likely to share similar evolutionary advantages to men. Note that I leave high status out of this equation.
Compare the mathematics to the evolution of culture:
a) There are numerous known cultural differences between what men and women grow up with. There are also many known mechanisms for which cultural meme merging is different for men and for women. Our culture directs different memes towards men and women, to a far greater extent than gene selection does (if it does at all).
b) High status women are in fact less likely to have many kids, as is shown by an abundance of demographic data. Therefore, the mechanism by which they can spread what's responsible for 'high-statusness' is limited mostly to memes. But culture strongly moderates this influence of dominant, high status, intelligent women. Consider the treatment Hilary Clinton is getting now. Even in a more ordinary circumstance, male bosses can wield power in a way that would label their female cohorts 'ice queens'. So the influence of powerful women is labeled a bad thing, and the adoption of those values by other women is severely inhibited.
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So, for this case, at first glance, it seems like the evolution of cultural memes completely dominates the influence of the evolution of biological genes. Does anyone see a hole in this argument?
a) Genes are not expressed the same way in men and women. To oversimplify a little, if a gene is only activated in the presence of male levels of testosterone, it will not be expressed in women. In the long run, natural selection hooks up genes that are beneficial in men and harmful in women to testosterone-sensitive gene promoters, though this may take a long time, and in the meantime you may end up with women with deleterious traits that were beneficial for their fathers.
While we're at it, similar mechanisms account for the difference between a neuron and a muscle fiber, which share identical genomes.
b) A very successful man can end up with hundreds of concubines and children. A significant percentage of Asians are direct descendents of Genghis Khan, and there was a King Niall in Ulster who is said to be an ancestor of 25% of the men in Northwest Ireland. Monogamy somewhat limits this in our culture, but most people for most of the time humans have existed have been polygynous. For a woman, this is impossible - she can have a dozen or so babies at best.
Gene expression is a good point. It was in the back of my mind (and I glossed over it completely), but you've succinctly explained why it's actually an important issue.
Do you have a notion as to the relative time for gene promoters to hook to a gene with sex dependent fitness? I imagine that the mathematics of evolution would depend to a large degree on gene <-> selector or gene <-> meme coupling.
Yes. The reference to cultural memes is a chicken an egg argument; by claiming "complete domination" you essentially overlook the origin of said memes.
I'm not armed with sources, but I daresay that nature has given everything specialization, so much so that applying the same ideas to the sexes is not the slightest bit strange. More strongly said, there is nothing surprising when one sex exhibits traits much more ostensibly than another. While I am not referring to the superiority of a specific sex, specie, or trait, it actually seems more unnatural to claim equality on things like attitudes towards risk and attribute difference to culture.
Back to your arguments specifically. These come from a fuzzy memory, but they provide a complementary view.
a. Even a single genetic difference can lead to drastically different results. We are close enough to chimps. Men and women have different brains; different areas activate up when shown the same picture. It's not a stretch to say that risk evaluation is done differently as well.
b. I recall at least two matriarchial societies in which women called the shots. Nevertheless, the men were still the fighters, which is perhaps the most competitive, aggressive, and risky behavior possible. Women can be dominant, intelligent, and decisive, and still partake in less adrenaline-laden activities. There may be something else in the motivation.
a. I think this is a good and important point, and am not trying to underplay it, but this argument is usually the convenient one, and the hardest to make any systematic observation. Thought experiment: try comparing startup founder numbers of Japanese men to those of American women.
b. Again, true enough, but also: the sperm of a high-status males, whom are shown to produce more offspring, still hold good chance to yield daughters.
you essentially overlook the origin of said memes.
I don't overlook the origin. Your thrust seems to be that culture only magnifies innate difference. Perhaps this is true in simple cases, but I think that there are particular examples where culture takes on a mind of its own.
I point out that existing cultural bias might be due to biological bias interacting with environmental factors long extinct. This bias is encoded and preserved, unlike almost everything else in the animal kingdom, in human culture, which can be perpetuated and passed on. Existing cultural bias might just be a carry over from prehistoric times, entirely irrelevant to whether or not there are now meaningful differences in aptitude, in this, the present.
it actually seems more unnatural to claim equality on things like attitudes towards risk and attribute difference to culture.
I never claimed equality, I simply pointed out that the differences you'd expect due to biological selection are smaller in magnitude than those due to cultural selection, and so therefore born-attitudes towards things like risk should be largely outweighed by cultural ones.
My mind wouldn't scream inconsistency if I heard that women, on average, were intrinsically, say, 30% less likely to take big risks. That kind of difference seems reasonable. But the data on entrepreneurship implies a difference many dozens of times that.
I don't think this magnitude is consistent with other risky behaviors -- many women do risky things as well, like dating strange men in remote places, running away from home, abusing hard drugs, or keeping a pregnancy in ill-health. This difference in magnitude may be explained by cultural factors, because men have greater cultural support when projecting high-status creating cultural memes (especially those encouraging risky behavior).
this argument is usually the convenient one
Perhaps I was unclear. This is a very different argument than the one typically given, because it uses the very same mathematics that the evolutionary biologists use, only applied to culture. And what you find is that the factors in culture -- the influence of the same kind of mathematics, is much stronger.
the sperm of a high-status males, whom are shown to produce more offspring, still hold good chance to yield daughters.
The easiest way to prove something is genetic rather than cultural is to examine different cultures throughout the world, especially isolated ones like pygmies or aborigines.
The paradigm of man as provider and woman as nurturer, and the mating ramifications of that (i.e. women preferring men who are able to provide, which most closely translates in our society to wealth, and men preferring women more fit to raise children, which in our society most closely translates to healthy appearance) are virtually universal.
That would strongly suggest that it is genetic rather than cultural.
The easiest way to prove something is genetic rather than cultural is to examine different cultures throughout the world, especially isolated ones like pygmies or aborigines.
I agree that this is easy, but I am not sure that it is in fact accurate. To do so you must show that the particular cultural values you're exploring do not share anthropological linage. This is a very difficult problem. How do you propose to handle that case?
The paradigm of man as provider and woman as nurturer, and the mating ramifications of that (i.e. women preferring men who are able to provide, which most closely translates in our society to wealth, and men preferring women more fit to raise children, which in our society most closely translates to healthy appearance) are virtually universal.
So would you draw the line from this evolutionary argument like so: men have a greater instinct to produce wealth or high status, which causes them to produce more startups.
The problem I have with this is that's its so vague. If we don't actually try to nail down or postulate an actual theory, people can be lazy and undisciplined in their thought. They might say, for example "here are some good reasons that the sexes might be intrinsically different; any existing difference is just the way things are, due intrinsically, and due to genetics". My point is that the disciplined way to approach this question is that you actually need to make specific predictions, or you risk degenerating into religious war.
So, in which ways is this instinct for men to provide manifested?
Compared to startups, law or medicine or finance seems a surer method to acquire status and prestige, and you probably come out ahead on average. More women are in these fields than in startups.
And physical science and engineering aren't particularly high prestige careers, nor do they make much wealth, nor do they seem to improve procreative chances. And these fields are particularly male centric.
So then usually someone points out that men like to take risks. They aim for the massive payoffs. If that's so, one should examine the structure of risks that men take versus women.
So, we have a set of hypotheses, backed up in varying amounts by data. Men are much more likely to do one off things to impress people. I guess this is called machismo. They're much more likely to take physical risks, or health risks. They may be more likely to take risks in their social stature, so long as they have little to lose. They're more likely to risk the state of a relationship for some impulse, someone or something that they want.
By contrast, I postulate, women are more likely to risk themselves emotionally. They are more likely to invest themselves in one particular friendship or relationship, even if it risks not panning out. Men, by contrast, fear commitment. They're more likely to keep their eggs out of one basket (see especially, for example, studies on the messaging patterns and viewing patterns and requests and satisfaction on dating sites). Women are more likely to invest themselves emotionally in some community, cause, person, or idea.
Doesn't this sound like a startup?
It's striking how many female entrepreneurs describe starting a startup like having a baby. Mena Trott (in founders at work) describes it like having a chemical in your brain that blocks out the painful moments, leaving only the other ones in memory (This effect is described also of pregnancy, and recently they've actually discovered that such a chemical exists). Are women more ready to devote themselves like this? Are women more emotionally prepared for a startup? Perhaps.
So, we have conflicting attitudes towards risk. On one hand, we postulate, men are more likely to be driven by promises of extreme status and wealth. On the other, women are perhaps more emotionally prepared, in some areas, when they get there. It seems like this should be a fairly balanced game.
But it's not. Female founders make up 3% of the YC pool. The risk and wealth hypothesis can't handle this alone.
Something has to take up the slack. And I think that it has much to do with the fact that different memes that define success in this society propagate to men and to women.
You can't simply say that since men are more hesitant to commit to relationships, and women less, that the same holds true in startups or careers, or that it translates at all. Both genders exhibit behaviors where mating is concerned that are very different from how they behave in other situations.
You should really read up on evolutionary psychology, I think you might enjoy it.
Existing cultural bias might just be a carry over from prehistoric times, entirely irrelevant to whether or not there are now meaningful differences in aptitude, in this, the present.
This is easy to show: superstitions and religions. Then, reverence of those closer to gods. Religion is almost completely cognitive, and so only humans are able to develop, propagate, and perpetuate it. It is also cognitive in the sense that children are not developed enough to invent it themselves. This fits the "entirely irrelevant" category.
But for other things that can be explained loosely by behavioral drift, the chicken and egg problem remains. Perhaps a small, innate difference was exacerbated by culture, creating a sustained, artificial specialization; this is also the byproduct of the human tendency to generalize. Not saying it's the most efficient, but in most cases I would say there is nontrivial relevance.
I never claimed equality ... a difference many dozens of times that.
This I agree with. The examples of risky behavior like dating strange men and running away though, I'm not so sure if they make good comparison; it is possible to look at these behaviors from another angle (behavioral/biological), but that's not to devalue the point you made.
About sperm of high status males. High status males produce more offspring, several of which can be females, who inherit the status. Upon rereading I realize I'm confused about this point. How are males's status not also spread through memes (disregarding relative degree)? I suppose you'd say they are, then what's the crux of saying that high status females produce less?
Another clarification, what kind of mathematics is that used by the evolutionary biologists?
Above questions are for my own interest and I won't follow up on them. I mostly agree with you, but I'm fairly sure "completely dominates" is an overstatement, and I went about throwing pebbles because you asked.
I guess I'm using 'entirely' and 'completely irrelevant' as literary flourishes, hoping that the qualifiers elsewhere modulate the meaning properly. But I guess that's a little confusing...
what's the crux of saying that high status females produce less?
My point is that, the same behaviors that men can use to achieve high status, if women use they're frowned upon. Even if they succeed in using said behaviors to achieve a higher status, cultural resistance applied a force restricting the spread of those memes to other women. (For example, talking behind someone's back about 'whipping' employees or coworkers, or ad-homeniem/targeted/unfairly focussed attacks, such as on Martha Stewart or Hillary Clinton or Kathy Sierra http://headrush.typepad.com/)
what kind of mathematics is that used by the evolutionary biologists?
Some do a lot of analysis, or combinatorics. I'm actually more interested in a complexity approach, in the manner of stephen wolfram, because there's a lot of complexity which I think can't be easily engineered out -- it's better simulated.
> the same behaviors that men can use to achieve high status, if women use they're frowned upon
To achieve high status, males have to endure much more than being frowned upon; the price of failure, historically, has often been death. You bring up Hillary, but compare the total weight of attacks on her with the total weight of attacks on McCain or Obama. Even if we take just the ad hominem ones.
"Even in a more ordinary circumstance, male bosses can wield power in a way that would label their female cohorts 'ice queens'."
I suspect that those male bosses are equally called names and disliked. They just don't give a damn.
I wonder if women bosses just have a bigger aversion to being strongly disliked?
(Rhetorical question here. I really don't know. I've had several different male and female bosses at this point, but haven't really experienced behavior from either that would make me want to call them bad names.)
a) irrelevant
b) I don't think anyone suggested that "dominant, decisive, intelligent, women" are any less likely to start startups than "dominant, decisive, intelligent" men. (I'd define the characteristics that drive one to start up differently, but you get the picture. However you define it, it may be that fewer women have those characteristics).
a) ok. undoubtedly a part.
b) Perhaps you have cause and effect bakcwards. Perhaps women with fewer kids are more likely to become high status. Perhaps both are just correlated and caused by some other factor.
And Hillary Clinton is getting a lot of the treatment she is now because her refusal to concede for a long time when it was clear that Obama would be the nominee has been potentially very destructive to her party. I'm not so sure a male candidate who did the same thing would be thought of any better, or at least not much.
a) irrelevant with respect to what? The point of this is that it contrasts with the case for memes. Memes are directed towards the different groups much more strongly, and so by that force you'd assume that they're more likely divergent.
I don't think anyone suggested that "dominant, decisive, intelligent, women" are any less likely to start startups than "dominant, decisive, intelligent" men.
That is in fact more along the lines of what i'm suggesting. I think that conditioned on the same startup traits, women are actually less likely to start startups due to cultural factors, of which one of the strongest is the cultural disincentive to risk. My specific claim is that the cultural disincentive strongly outweighs the innate tendency.
I'd define the characteristics that drive one to start up differently
I too, but these were the traits on topic.
b) Perhaps you have cause and effect backwards.
My central hypothesis was that women, currently, face more resistance than men in spreading any memes that create high 'provider status'. And that under the model postulated, you'd expect the evolution of memes to dominate genes.
And Hillary Clinton is getting a lot of the treatment she is now because her refusal to concede for a long time when it was clear that Obama would be the nominee has been potentially very destructive to her party.
Her maltreatment long preceded that moment -- the media has consistently typecast her as 'icequeen' or 'man', and I have heard that sentiment abundantly reflected.
Irrelevant in that sharing "mostly the same genes" still leaves the door open to vastly different physical and psychological makeups. It's a given to say that men and women are very different physically (hell, our brains even have noticeably different shapes) yet it's taboo to say we might be different psychologically.
> b) Dominant, decisive, intelligent, women are likely to share similar evolutionary advantages to men.
Unfortunately women like that are incompatible with many human cultures. E.g. try being a dominant, assertive woman someplace with Sharia law. Historically, those traits were bad for survival in many parts of the world.
Or women were treated like chattel and were property of men, and they didn't get a say in who they mated with. So their intelligent genes would be diluted. Or look at Darfur -- it's rape rape rape all the time. Being good at Sudoku requires a certain level of societal stability before it's really that handy.
Basically, men aren't as important as women. If 99.99% of men died today, the human race could be back to it's normal population within a generation (a man could easily father a child a day for 30 years ~10,000 children). On the other hand, we'd have much more trouble if 99.9% of women died, since a women can only realistically have about 10 children in a lifetime. This encourages men to be bigger risk takers - women were the limiting reagent to population growth.
Similarly, the potential gain for a ridiculously successful man (genetically speaking) is that he can have several thousand children. A women, on the other hand, can likely have 10 children whether or not she is successful; so there is little (evolutionary) benefit for her to be hugely successful (or take risks necessary to do so).
A women, on the other hand, can likely have 10 children whether or not she is successful
Surely you are joking... Miscarriages, even a century ago, claimed so many women. You would be lucky to live past your third, much less your tenth!
Without some network to provided for her (either by her family, or the village, or her mate, all of which are strongly effected by status), the likelihood of surviving a pregnancy becomes much lower.
Women couldn't just flip a switch and get pregnant to satisfy a biological urge. Pregnancy represents both an enormous investment in time, effort, and energy, and a gamble on life. Status structure reflects this.
Families with nine or ten children weren't all that uncommon in my grandparents' generation here in Taiwan.
Even today, there are ten different countries in which the fertility rate is currently above 6 and a couple above 7. I don't think 10 children would be unreasonable as an upper bound for the exceptionally successful.
Oh, and the 10 was an upper bound. If it's 3 that's even better - women are even more of a limiting reagent and they have less of a evolutionary need for massive amounts of wealth.
My theory is that there are two types of fundamental 'evolutionary units' that are important when discussing humans. Memes, and genes. I agree that, when memes were unimportant, the genetic influence, for females, of an outstanding capability to provide, would be largely wasted.
However, massive wealth only became possible once human culture grew, and then, for reasons I outlined below, memes became far more sticky, more influential, and more important, by comparison. In this, women have a greater evolutionary incentive to gain wealth or prestige or spread memes, but not a greater genetic incentive.
fair enough. Let me rephrase to say that a moderately successful women (on the par of a low level aristocrat) could easily support 10 children. It still supports my contention that men had more to gain from being hugely successful (king level) than a women.
I remember once reading that before modern medicine, 1/4 of pregnancies ended in death to the mother due to the baby's size. That would certainly explain why women don't take mating lightly.
"The historical level of maternal deaths is probably around 1 in 100 births." However: "Mortality rates reached horrible proportions in maternity institutions in the 1800s, sometimes climbing to 40 percent of birthgiving women."
"Also, the life expectancy for women was lower throughout history than it was for men; because, until the advent of modern medicine, one in four women died in childbirth."
I had heard this statistic originally in some atheist propaganda video, hilariously enough.
While that makes for a neatly packaged Darwinian theory, it's important to remember that genetic selection is not the only force that affects our decisions. Medicine, culture, technology, and many other factors affect, and even override, what our genes may steer us toward if they could "act in a vacuum."
Not convinced? By the same theory, one would think that men in today's society would be highly encouraged to have children with multiple partners -- at roughly age 18. Yet, we discourage both for no apparent genetic benefit. Rather, it's for a societal benefit.
Unfortunately, Darwinian theories about "women being wired for different work than men" are perpetuated at all levels. (Anyone remember Lawrence Summers at Harvard?) And because people actually begin to believe the theories, they become in themselves a form of subtle discrimination that both discourages women from attempting certain activities and prevents them from being offered certain opportunities.
It's really important not to belive it yourself and to consider all the many factors at play here.
Men have always been encouraged to have sex with a lot of different partners, not to sire children with them. (Children were, of course, the reason that men developed the urge, but the urge stands separately, as shown by the fact that men do not decrease their mating habits when there is no chance of pregnancy.) That's clearly still the case in modern society. Spend 10 minutes in a high school locker room and you'll see that.
Darwinian theories about women being wired differently than men are perpetuated because science backs them up. We don't know exactly how, or how much of the difference is genetic vs. cultural, but it's just a reality that men and women have different motivations, aptitudes, etc.
Nobody would argue that evolution has made us different physically. Men are much stronger and better coordinated. Women are more able to bear pain and often have stronger senses of smell and taste. Why would it not stand to reason that evolution might make each sex better at some mental tasks than the other, just as it has physical? It's not sexist to point out that male weight-lifters are able to bench more because men have been designed by evolution to be stronger. Why is it sexist to say we show up more frequently in science departments because we have also been designed by evolution to be better at math?
Sexism is not believing that one sex is different than another, it's believing that those differences make it inferior.
Why is it sexist to say we show up more frequently in science departments because we have also been designed by evolution to be better at math?
Because compared with bench-pressing, claims of mathematically ability being better in men (and partially ordered, to boot) is seriously jumping the gun.
We know what's involved in a bench press. We understand how testosterone stimulates the production of muscle. We are nowhere close with mathematical ability. We have no theory of mathematically ability -- we really don't know what it means, or if the simplest metrics are even useful for higher level math. We have no experimental results, because we have no controlled variables. We have few pieces of data, none of which are conclusively disentangled from cultural and historical influence.
In the past two decades, the number of women scoring highly on the IMO, the IOI, the Putnam, and SMPY has gone up by roughly a factor of six. Doubtful that the number of girls with 'math talent genes' have sextupled that quickly. Isn't this evidence that we should hold off on our conclusions?
I don't think anyone would claim that we know or understand all of those differences yet. I don't even really have an opinion on the math one, it's just the most commonly cited so I used it as example.
But we need to be open to the fact that they are there. It hinders scientific and social progress to scream sexism any time someone suggests the sexes might be different in some way.
It hinders progress in the same way to scream anti-sexism when what is really being suggested is a reasoned discussion.
It might be absurd to assert equality, but it's a decent postulate to take while we don't know for sure. And I think asserting the certainty of particular innate differences, without sufficient evidence, is more dubious than the corresponding assertion of equality.
Well, the one thing we know for sure is that we're different. We just don't know all of the why's and how's. So overall equality (in the sense of similarity) is the only thing we know to be incorrect.
Lawrence Summers, if you read or watch the talk, did not, in fact, assert that the dearth of women in science was explained by biological factors. He brought up the question. Even considering the insufficiently delicate way he put it, there's an exceptionally important distinction. Unfortunately, people heard what they wanted to hear.
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Not convinced? By the same theory, one would think that men in today's society would be highly encouraged to have children with multiple partners -- at roughly age 18. Yet, we discourage both for no apparent genetic benefit. Rather, it's for a societal benefit.
As I note below, often societal benefit trumps genetic benefit, which remains true as long as there is a high genetic correlation between the people in that society.
There is a difference between acknowledging a difference exists, and acting on that difference in a discriminatory manner.
Women and men are wired differently. That much is a fact. The obvious, those of reproductive organs, are visible and nobody would deny them. Those in the head, are invisible and so somehow made into a sensitive issue, but significant differences exist. Women have a larger corpus callosum than men; one could suppose then, that their hemispheres talk faster with each other: efficient multitasking. There is nothing wrong with this step: it is the same kind of reasoning that you apply to saying that giraffes have long necks to eat food in trees.
The problem about discrimination is what happens after this step: a man is unable to multitask. A giraffe is unable to eat food that is not in trees.
But these are two things. And most knee-jerk antidiscriminationist rhetoric lumps them into one. Also, I am not calling you one :)
The problem about discrimination is what happens after this step: a man is unable to multitask. A giraffe is unable to eat food that is not in trees.
We are in agreement, and I give you credit for explaining the point better than I did.
I also probably should have been more specific when I said it's dangerous to believe that "women [are] wired for different work than men". I'm not arguing that women and men are the same in every way. Clearly there are differences. I'm saying it's unfortunate to take a problem like the low number of women founders and to use Darwinian theory to say "women just aren't wired for this type of intellectual work." This makes it all too easy to overlook other causes of the problem and, as you point out, can lead to discrimination in various forms.
Indeed, someone just posted this timely article on HN today about a study showing that "boys are not innately better at maths than girls, and any difference in test scores is due to nurture rather than nature."
http://education.guardian.co.uk/schools/story/0,,2283083,00....
From a Darwinian perspective, you are of course right.
I think that potential pregnancy is a factor. The hours traditionally worked by startup founders could be detrimental to health, and the inability to take prolonged breaks from work at CEO level is probably a deal-breaker.
(Some of the best salespeople I know are female, particularly in consultative selling.)
RE-EDIT: Sarcastic thanks for the downvotes. And sincere thanks to whoever upvoted. I feel better!
This may be true. However, I do know some very smart women who have gotten pregnant accidentally.
It's claimed (by?) it takes an average of 7 years to exit your startup. That is a large chunk of time for women with a ticking biological clock. I do realise of course that it is possible to have kids in to your 40s, but most women choose not to do so.
That implies that women have a greater biological imperative to reproduce than men. I don't know that that's true.
Honestly, I see my "grad school clock" as an equally big, if not bigger, problem than anyone's biological clock. When you do a startup, you have to choose your priorities -- the implication is that neither kids nor grad school are amongst them.
Women certainly do have a greater biological imperative to reproduce than men. It's for the very simple reason that a woman's fertility starts declining in her early 20's and bottoms out around age 40 -- a man's fertility erodes very slightly and is usually in perfectly serviceable condition at age 60.
Kids take a lot of time, granted. But grad school? It takes 4-5 years (1), and during that time, you can work on your startup part time. You also develop technical skills, which you can later use to work outside the (somewhat crowded) webapp space.
(1) The average is 6 years, but that includes lots of lazy people, future college teachers, people who enjoy grad school, etc. Potential startup founders would almost certainly be faster.
Besides aggression, the explanation that I've heard that makes the most sense revolves around risk: men can effectively have more than one mate (and do in many cultures, especially non-western), so there's more benefit to genetic risk-taking in men. This isn't a big effect, but is very noticable at the ends of the bell curve: more male serial killers, more male ceos.
Anyway, take all evolutionary psych with a grain of salt, but it's interesting to talk about.
All of this would certainly be valid if women and men were separate species. It would also certainly be valid if females of the human race had specialized into something reminiscent of a queen bee or ant. I don't know if that is or is not the case, but I know where I'll put the burden of proof.
In a darwinian sense men and women are profoundly different and have seperate tasks to perform in the process of creating offspring. This inevitably leads to natural selection acting differently on men and women, as exemplified in the above post.
What characrerises reproductively successful men? Or, to put it another way, what qualities do women seek in a mate? Women tend to prefer dominant men of high status with lots of money, and there is little reason to believe that their ancestors differed. For much of human history male status came from being a skilled hunter and warrior and from the ability to influence others through muscle or wit. This history has left men more disposed than women to strive for status and engage in the risky, competitive and sometimes aggressive behaviour often required to do a successful startup. Women with a taste for winners would likely be in a position to pass their preference on to more children than would women with a penchant for failures.
Women would not ordinarily enhance their reproductive success through direct competition and risk-taking. Indeed, it would promise little reproductive payoff and could be a very dicey strategy because a bad outcome would imperil a woman's future reproduction and the well-being of existing children. Instead, women, to a far greater extent than men, have enhanced reproductive success by looking after their children as they grow up, resulting in stronger bonds between mother and child than between father and child.
This explanation also hints at the fact that women would make good CEO's of large corporations where security is more important than risk taking.
Note: this isn't in in any way meant as a degradation of women - merely a possible explanation of the cause.