Having children changes a man. All of us know examples of that. I’m pretty sure, for instance, that the only time I ever saw my father sing was to his kids. It wasn’t always pretty, but it was pure Dad.

But is there something about fatherhood that actually changes the male brain? Studies suggest that it does, including one published a few years ago which found that new sets of neurons formed in brains of mouse dads that stayed around the nest after their pups were born.

Still, there’s much yet to be learned about the effects of being a father. And so scientists continue to explore the eternal question: “What’s with this guy?”

Here are 10 recent studies deconstructing dad:

1.The upside to an old old man: So what if they’re only good for one throw in a game of catch. Old fathers can do something for their kids that young dads can’t–pass on genes that give them a better shot at a long life. A study published earlier this week in the Proceedings of the National Academy of Sciences says children of older fathers–men who wait until their late 30s to have children–inherit longer telomeres, caps at the end of the chromosomes that protect them from degeneration. And that seems to to promote slower aging and likely a longer lifespan for those kids.

2. See what I do for you?: Most dads know they’re going have to make a few sacrifices for their kids, but lose testosterone? Who knew? A recent study of 600 men in the Philippines found that testosterone levels dropped considerably after they fathered children. Scientists were quick to counter the notion that raising kids makes someone a less manly man and instead concluded that men’s bodies helped them evolve hormonal systems that make it easier to commit to their families. And the men who spent the most time taking care of their kids had the lowest testosterone levels, suggesting that biology helps them shift into parent mode.

3. And see what I do for you: Looks like being a dad may be good for your health. According to a study published last fall, fathers are less likely than childless men to die of heart-related problems. While the scientists acknowledged that their research didn’t prove a definitive connection between fatherhood and reducing fatal heart problems, the size of the study–it involved almost 138,000 men–gave credence to the belief that having kids improves your odds of dodging ticker trouble.

4. This is how you return the favor? Apparently, that healthier heart thing doesn’t go both ways. A study published in The Lancet earlier this year concluded that sons who receive a certain genetic variant on their Y chromosomes from their fathers were 50 percent more likely to develop heart disease than those without it.

5. Who needed all that testosterone anyhow?: At-risk men are less likely to drink, use tobacco or commit crimes after they become fathers–particularly if they have their first child in their late 20s or early 30s. Researchers at Oregon State University said the decreases in bad behavior went beyond what comes simply with young men maturing. Said lead researcher David Kerr: “This research suggests that fatherhood can be a transformative experience, even for men engaging in high-risk behavior.”

6. Of mice and men: Researchers in California have determined that more anxious mice make lousy fathers. Further tests showed that less paternal males had higher levels of vasopressin in their brains. That’s a hormone strongly associated with stress and anxiety. The scientists stopped short of saying stressed-out men struggle as fathers, but do think that what they’ve learned about mouse fathers could shed light on the behavior of anxious human dads.

7. The unkindest cut: A father’s love–or lack thereof–can have a greater influence on the shaping of a child’s personality and development than the mother’s. So says a recent wide-ranging analysis of research about the power of parental rejection. The research, based on 36 studies from around the world and involving 10,000 participants, concluded that nothing has as strong or as consistent an effect on a child’s personality development as rejection by a parent–an experience that can make them feel more anxious and insecure, as well as more hostile and aggressive. And the research suggested that it’s often the father’s rejection that has the greater impact.

8. Diapers…the final frontier: The idea that men have truly become involved in the raising of their children only in the past few decades just isn’t true, says a University of Warwick paper published yesterday. What has changed is that many more fathers now are willing to make the ultimate expression of love–they’re changing diapers. Figures from a 1982 study suggested that 43 percent of fathers had never changed a diaper. By 2000, that figure, according to another study, had fallen to 3 percent. Which makes you wonder: How did the 3 percent pull that off?

9. Bowed by the weight of dirty diapers, but not broken: A large majority of American men now say they place more value on being a good father than on having a successful career. That’s according to a survey of 1,000 men–both dads and non-dads–which found that a full 77 percent said doing a good job at home was very important to them, while only 49 percent felt that way about how they performed at the office. The Mad Men are so over.

10. You’ve come a long way, baby…and yet: Despite the strides fathers have taken in manning up around the house, they still have a way to go if they hope to go halfsies with their partners. The latest Father’s Day Index, published on the Insure.com website earlier this week, estimates that if the average dad was paid for what he does at home, his income would be slightly more than $20,000. Based on Bureau of Labor Statistics data, the value of what moms do at home is about three times that.

Video bonus: Sure, more fathers now embrace diaper-changing, but for some, it remains a great crucible. And as a Father’s Day Special, here’s an extra video of a dad who is moved to take desperate measures to deal with a baby daughter who won’t sleep.

Read about our 10 Studies That Deconstructed Mom