Hmm. My eyes fall upon his sleeveless T-shirt. I imagine pouring my drink on it. My friend Jon tells me that these are “intrusive thoughts” and everyone has them. Which gives me permission to also imagine setting the shirt on fire. Ah, peaceful lakes! Birdsong!

I know I’m not a fun first date. I want to ask prospective partners whether they want to become parents and when — and excuse me? You haven’t given it much thought? A shrug from a man who already has a couple of gray hairs strikes me as wild arrogance.

This arrogance has, as I see it, two main causes — one, a belief that their spermatozoa are good for a very long time, indeed, and two, a belief that they could get a younger woman if they wanted to. Let me examine the evidence for each of those male beliefs; fertility first.

Your sperm is not immortal. A study that tracked 8,559 pregnancies found that “conception during a 12-month period was 30 percent less likely for men over age 40 years as compared with men younger than age 30 years.”

That research was gathered in 2000 and was one of the few studies that focused on male fertility. See, scientists have invested a lot of time in poking and prodding women to understand conception, but only a small fraction of those studies have controlled for the age of the father. In other words, all that data we have about how women in their late 30s are struggling to get pregnant doesn’t take into consideration the fact that many of those women are trying to conceive with men who are in their 40s.

Men are much less fooled when it comes to that second belief — that they could get a younger woman if they wanted to. I’m not just basing this on the Census Bureau data I cited. There’s also the information gleaned from OkCupid’s millions of preferences. The dating site’s researchers found that most conversations take place between an older man and a younger woman and in almost half of them, the age gap is at least five years.