The smell of man sweat doesn't have so much to do with him as it does with us. According to a study in the journal Nature, a dude's B.O. is all about perception, due to a receptor gene. So for some people, a sweaty guy could smell like hoagies, for others he could smell like urine, and for others he could actually smell like sweet vanilla. The chemical androstenone is in the sweat of both men and women, but it's more pronounced in men, and is created when the body breaks down the male sex hormone testosterone. Scientists said that the slight genetic variations in the receptor, called OR7D4, determines how we "experience odors." So why is this important to us?

It facilitates the courtship behavior in females.

So it would seem that men are no longer to be held accountable for their nasty ass-stench, because it's our problem not theirs! What other stuff was discovered in this study? We ladies are likened to pigs:

The role of androstenone is not well understood [on women], but in pigs it sends a powerful sex signal that puts sows in the mood for love...There is some evidence published showing this chemical can modify the mood or hormone levels in humans.

The scientists involved in the research say they will further study how smelling these chemicals might affect human social and sexual behavior.

Stinky? It's Not His Sweat, It's Your Nose [Reuters]
Related: Do People's Smells Change When They Get Turned On? [Esquire]