What is it about masculinity, that it seems to be so easily threatened?

@Simone posted this article about redefining our views on fertilization. It’s a fascinating article from the biological perspective, but it’s equally fascinating in a sociological/anthropological way.

One of the main threads of the article is how our language regarding fertilization and the interaction between sperm and eggs is skewed, incorrectly, to reflect our views regarding gender. We use strong, manly, virile, and potent imagery regarding sperm and rather unexciting, passive, lady-in-waiting terms for the egg.

In the article, Dr. Martin (the researching anthropologist), mentions a few times that men aren’t comfortable thinking their sperm are anything but warriors conquering that egg. It got me thinking.

Now, being gay and never having had a boyfriend, my intimate knowledge of men is more limited than, say, a straight woman. So my views here are based on observation and, yes, generalization, but I’m hoping you can forgive and/or look past that to get to the heart of what I’m asking.

It seems to me that one of the important qualities of being male is one’s masculinity and that a lot of interesting male behaviors stem from trying to keep up the appearance of one’s masculinity or from feeling that one’s masculinity is threatened. I feel like a lot of stock is placed in men toward the importance of “being a man”. For example,

- having such a difficult time admitting one’s sperm isn’t strong
– that one might not be fertile/potent
– how embarrassing it is for a guy to be missing a testicle or both
– feeling threatened by male homosexuals
– feeling threatened by the idea of being penetrated despite the fact that prostate stimulation is apparently quite pleasurable
– strongly preferring to be the ‘strong’ one, the provider, “the man”, “the protector” in a relationship
– I can think of loads more, but we’ll go with that for now.

It seems like there’s a male culture of… I’m not sure how to put it… requiring an invulnerable masculinity. If a man doesn’t stack up, he can feel low self-esteem and self-worth, simply for not being “man enough”. It’s this desire, almost a need, to be “a man” that I find really interesting and that I’m hoping to understand.

So.. why this comparison of masculinity all the time? Why is masculinity so important to men? And why does it seem to be something that’s easily threatened?

And anything else that you might consider a propos or interesting.