The human phalllus. Why?

I hope this post doesn't come across as stereotypically gay, with me dedicating a post showing obsession with the human phallus. Because that is not the point of this post.

Rather, I came across this article when reading through recent science headlines. Turns out that Scientific American has posted an article "Secrets of the Phallus: Why is the penis shaped like that?" And despite being written by a gay writer, he even states during the article:

Now the irony doesn't escape me. But in spite of the fact that this particular evolutionary psychologist (yours truly) is gay, for the purposes of research we must consider the evolution of the human penis in relation to the human vagina.

So don't worry, heterosexuals have nothing to fear from this article.

Why is this article worthy of posting? Because it answers why. Why is the human phallus so large, relative to body size, compared to all other primates? Why are humans the only primates that have a "mushroom-capped glans" at the head of the phallus? In particular, why is the coronal ridge of the glans wider than the shaft that supports it?

Go ahead, read it, and know more about how we came to be so well endowed.

(Day 328)