I spent much of the (so far) middle of my life pursuing big/deep questions. That’s what I focused on in each subject I learned, that’s what I liked most about the first topic (physics) I specialized in, and that’s what drew me to each new subject as I switched.
It was good that I was able to stop jumping to new subjects, so that I could actually accomplish things. However, as I long avoided studying biology (too much disorganized detail!), but recently found an excuse to focus there, I’ve been enjoying my old pleasure via deep questions of biology. For example, I’ve long heard talk on the puzzle of why sex exists, and have heard many plausible arguments on why sex (mostly) won over asexual reproduction. But until a few days ago I hadn’t noticed a harder puzzle: why do most animals, but not most plants, have males?
Most plants are hermaphrodites; each organism has both male and female genitalia. Plants thus gain the many advantages of recombining genes from multiple parents, while also ensuring that each organism contributes fully to reproducing the species. Most animals, in contrast, reproduce via pairing one male and one female, with females investing more than males in children. In such species, males and females differ in many ways that can be understood as resulting from these differing investments in children.
Many of these differences seem to be costly for the species. For example, not only do males spend most of their resources competing with each other for access to females instead helping with children, their competition often directly harms females and children. In fact, species where males differ more from females go extinct more quickly:
When comparing species, it emerged that those in which males were very different from females had a poorer prognosis for continued existence. The authors’ models predict a tenfold increase in extinction risk per unit time when species in which males are larger than females, with large differences in shape between the sexes, are compared with species in which the males are smaller than the females, with small differences in shape between the sexes. (more)
And yet males exist, at least in most animal species. Why? More monogamous species, like humans, where fathers invest more in kids, are less of a puzzle, but they remain a puzzle as long as males invest less. As plants show that an all-hermaphrodite equilibrium can robustly last long for complex species, there must be some big positive advantage to having males in animal, but not plant, species.
After reading a dozen or so papers, I can report: we just have no idea what that advantage is. One person suggests males are “an ‘experimental’ part of the species that allows the species to expand their ecological niche, and to have alternative configurations.” But this idea doesn’t seem to have been developed very far, and why wouldn’t this work just as well for plants?
The robust existence of animal males strongly suggests that we men have an important but-as-yet-unknown mission. We offer a gain that more than pays for our many costs, at least in most animals species. And yet our costs seem much clearer than our gains. We men might feel a bit better about our place in the world if we could better understood our positive contributions. And yet very few people study this deep question, even as vast numbers remain very engaged discussing human gender politics. That seems a shame to me.
Added 9:30p: Plants do compete for and select mates. It isn’t obvious that mobility allows far more such competition.
Added 4a: You might have seen evolutionary competition as overly destructive, but existing because more cooperation requires more coordination, which is hard. But the existence of males shows that, at least for animals, evolution saw “red in tooth and claw” competition between hermaphrodites as insufficient. So evolution created and maintains an even stronger kind of competition, between males who need invest less in children and can thus invest even more in competition.
Sorry to be late to the discussion, I only just discovered this blog. As a female, I must say it is unexpected but rather refreshing to find a discussion taking place largely amongst men, which is pondering the utility of men's very existence.
However, I don't think the answer to the question is very difficult to find. My take on why males exist:
1. Diversity: if women get to choose which men to mate with (believe me it's not a given that the woman always gets her choice!), they can choose the best available genes to produce offspring. The choice can be adjusted for the environment/circumstances they find themselves in, so it allows the species to adapt more quickly. Diversity of selection strengthens the survival chances of the species.
2. Usefulness: Having husbands/fathers around can be very useful. On average, men are larger, stronger and faster. If they act in the interest of the family as a whole, they can contribute great value for many practical matters. This is clearly an aid to survival of the species.
(Note: best providers of genes and best husbands/fathers are not necessarily the same group, thus we see some men nurturing other men's genetic offspring).
3. Women like men and enjoy their company: despite what men may think, women do actually like men when they are behaving like reasonable human beings. Women place great value on the love, affection, romance, empathy, understanding etc to be found in a good partner. Whilst I'm not sure how to quantify this in terms of how it aids the survival of the species, it is one of the things that makes that survival worthwhile. Perhaps we can say it gives the species the will to live, because it makes life enjoyable. (The question of whether there is any point in surviving simply for the sake of survival itself could perhaps be debated elsewhere....)
Dimorphism came from natural selection, which resulted in a species that made it to the top of the food chain, and we've kept that status ever since.
It didn't happen because we were the biggest and baddest. It happened because of our social ability, our intelligence - and, including but not limited to, features of brain cells in our limbic system that would shut down when facing danger, allowing our crowning evolutionary achievement of executive function to don the day. The fact we're philosophizing and intellectualizing our own existence is evidence of our uniqueness that put us on top.
We're all human animals, female, male, androgynous alike, whether we like it or not. But we're unique enough it's really a waste of time to engage in comparing us to other species at such fundamental levels, especially those species at the bottom of the food chain. However, we still suffer heuristic, cognitive and social biases, and thinking errors from the animal within.
Dimorphism was essential to survival and our social nature survival during the Stone Age. The problem is although we're out of the Stone Age, it is still within us. Even our dimorphism is obsolete.