"past research showing that married men tend to be healthier and happier than unmarried men"
That's an interesting observation, but I've read otherwise here. Most married men tend to have children.
THE GIST
The male hormone fell by 34 percent after men became fathers.
Testosterone levels in more than 600 men showed marked declines in salivary testosterone.
Research in some primates has shown that when a father sniffs the scent of his own babies, but not strange babies, his testosterone drops within minutes.