In 1665, the Black Death was sweeping across Europe.

In northern England, in a small town called Eyam, a tailor received some cloth he had ordered from London. He shook out the cloth and hung it to dry, intending to make clothes for an upcoming religious festival.

What he didn’t — and couldn’t — know was the cloth was infested with fleas infected with plague.

The tailor died quickly. Soon after, many others followed in death.

As the pestilence swept through Eyam, the surviving villagers met and decided they would go to London where doctors and medicine could be more easily found.

William Mompesson, the village clergyman, stepped in and suggested the unthinkable: that the village quarantine itself to prevent the plague from reaching nearby towns and villages.

Though it meant almost certain death for almost half the villagers, remarkably, they agreed.

They felt it was the right thing to do.

In just more than a year, 260 of the village’s inhabitants died. While the exact population of Eyam at this time is unknown, historians believe the death toll was about half of all townsfolk.

Eyam is now known as the village of the damned.

Yet I believe it should be called the village of the angels because the brave and altruistic choice to isolate the Black Death saved thousands of lives.

It’s a perfect example of the Trolley Problem in ethics.

If a trolley is speeding toward you, would you sacrifice yourself (or kill a single person) in order to save five people’s lives?

Science defines two types of altruism: kin selection and reciprocal altruism.

Kin selection speaks to the human tendency to sacrifice only for those people who share our bed or our genes. It holds that we might lay down our life for our spouse or children, but not for a stranger.

Reciprocal altruism is tit-for-tat, or doing something for another to receive something in return.

But to be considered “purely altruistic,” a person must sacrifice their time, energy, material possessions or life without expectation of compensation.

Because humans would tend to at least feel some satisfaction for their sacrifice, many psychologists agree true selflessness does not exist.

They follow the leadings of Thomas Hobbes, the English philosopher who believed man is inherently selfish and requires social order to reign in his greedy, self-centered nature.

I disagree.

I believe humans have the capacity for great acts of sacrifice.

The villagers of Eyam were not related to the strangers whose lives they saved. Nor did they receive anything for their sacrifice, except perhaps a feeling of satisfaction that they were doing something noble and right.

I not only believe humans are giving, loving beings, I believe we can cultivate altruism using something called the neural Golden Rule.

Humans are wired with mirror neurons, a type of brain cell that responds equally when we perform an action and when we witness someone else perform the same action.

These neurons will fire when you smile and also when you see me smile. They are essential brain cells for social interactions, because without them, we would likely be blind to the actions, intentions and feelings of other people.

Basically, the human brain tends to blur the distinction between other people and the self. So the more we tend to vicariously experience the states of others, the more we are inclined to do unto others as we would ourselves.

Neural Golden Rule. Get it?

So then why are there so many people who act like selfish jerks?

Why do we have racial prejudice and homophobia and misogyny?

If humans are altruistic by nature, why do crime, murder, rape and genocide exist?

Remember I said humans have the capacity for altruism. The answer lies in what we do with what we have.

Mirror neurons work for negative and positive experiences. So if you were raised in a household — or culture — that denigrates Jews or blacks or women, then you probably will too.

If you hang out with people who disrespect the law, then you probably will too. If you fill your time watching people spread senseless violence without remorse, then … well, I think you get my point.

It matters a great deal then to choose how — and with whom — we spend our time. To be selective in choosing what books we read, movies we watch, podcasts we listen to. These choices will invariably shape us into either more selfless or more selfish people.

Think of it as preventive medicine for your soul.

When the plague sweeps through, you’ll make the right choice.

Erin Smith is the owner of the OM place in Winchester, the author of “Sensible Wellness” and the online host of the OM channel. Follow her on Twitter @erinsmithauthor.