New York City’s subway system is a microcosm — or Petri dish, depending on your view — of humanity.

Nowhere was this more evident than as I made my way recently from Queens into Manhattan and observed the following all within the span of 40 minutes:

* A stranger (a man) helping a woman carry an ungainly stroller up a steep flight of stairs to a subway station.

* Two teenagers (both boys) rushing to grab the few available seats on the subway when there was clearly an older man who was eyeing a seat and certainly could have used one.

* A man entering the subway car, struggling with a stroller and awkwardly carrying his daughter, who was maybe a year old. A young woman offered her seat to the guy, who accepted it with a mixture of relief and gratitude.

Big props to the guy who helped the lady with the stroller and the woman who offered her seat to the guy with his young daughter. And a smack with a hard-cover book of manners for the two dolts who were oblivious to anybody but themselves.

It reminded me of the old Goofus and Gallant comics that were a feature of “Highlights” magazine when I was a kid. Presented with the same set of circumstances, Goofus would choose the path that was either rude or selfish and Gallant would do the thing that was chivalrous or polite.

What I am seeing increasingly in the world is too many Goofuses and too few Gallants.

I am not saying I am a perfect gentleman all the time but I think I have some sense of courtesy. Maybe it is the product of 12 years of Catholic education.

Seared in my memory is an episode from seventh-grade math class with Sister Margaret Marion.

A bunch of math equations were on the blackboard and myself and another student, Corrine Cortes, at the board to solve them. When we were done, I erased my work and handed Corrine the eraser.

In a voice that still echoes in my head, Sister Margaret boomed: “A real gentleman would have erased the board for her.”

Duly noted, sister. But being courteous is a practice that is gender-neutral.

I feel like a fossil saying this, but everyday manners seem to be as antiquated as Internet Explorer or black-and-white TV.

Gestures, such as holding the door for someone or offering a stranger a hand with their bags, seem like relics that belong in a museum for future generations to marvel at.

Maybe we are averse to interacting with strangers because the world is an unpredictable place filled with outbursts of violence.

Maybe we are too absorbed in our damn smartphones to ever look up and see a person in need.

Or maybe there is an entire generation that is too socially awkward to interact with others because it grew up spending so much time in front of computer screens.

I am not sure of the underlying causes but I do know that it costs nothing to be courteous but it can invaluable to the recipient.

So let’s see if we can all do our part, even just a little bit, to improve how we act toward others.

Please. And thank you.