There was Donald Trump just a year and a bit ago, trying to drag an entire country down with him and having some success in the enterprise.

There’s Jair Bolsonaro, flailing around as he awaits almost inevitable defeat by ‘Lula’ in next October’s Brazilian election.

There’s Viktor Orban, astounded to face a united six-party opposition in Hungary’s April elections.

And what they have in common is that they are all liars. Not shy, sly liars. Bold, in-your-face, shameless liars. They don’t care if you really know the truth from personal experience. It doesn’t bother them that you know they are lying. They will just say the lie again – and you might even believe them, because they say it with such conviction.

They are convincing because after a split-second when they privately decide that some lie will serve their purpose, they actually believe it themselves. They have other markers, too: they are usually male, they are always intelligent, they are almost always charming, and they generally get through several spouses and many children in a lifetime. They are, in a word, sociopaths.

Almost all confidence trickster are sociopaths, but the reverse is not true. Sociopaths can also end in the highest positions in business, in the professions, even in politics. (Not so much in the military, where they tend to get found out early.) And in recent times, they have been showing up in the highest political offices in many countries. Why now?

Which takes me back to an interview I did with a sociologist in an American university many years ago. He had written an article about how evolution had shaped human marriage customs, which somehow fitted into some radio doc I was doing at that time. God knows.

Anyway, we had finished up, and as I packed my gear I casually asked if he knew of any evolutionary circumstances that were changing human behaviour now. He paused for a moment, then said that he thought the sociopaths were multiplying. So I unpacked my gear and resumed the interview.

He began with the obvious statement that sociopathy is usually if not always a genetic property. Most sociopaths are born, not made. And he speculated on how they could have escaped being weeded out by natural selection back in the hunter-gatherer days, because those were small groups of people – thirty or forty adults – where everybody knew everybody else.

His answer was that small groups are not very vulnerable to a sociopath. Everybody has his number before he reaches reproductive age, so he can’t be a super-spawner. Everybody checks his lies with everybody else, so he doesn’t get away with much. And there are certain rare circumstances where it could be handy to have a sociopath around.

Hunter-gatherer bands are normally not just egalitarian but literally leaderless. However, little groups that can suddenly face existential crises – a famine, a rival band – need somebody in reserve who can provide ruthless, charismatic leadership. He’ll be almost an outcast in normal times, but one day you might need him, so don’t breed him out entirely.

All went well until human beings started living in societies thousands or millions strong where the sociopaths become invisible. Nobody has their number, and there’s an endless supply of strangers to deceive and exploit (and breed with).

A mass society is a sociopath’s garden of delights. Of course their numbers are going up: my sociologist friend reckoned 3% of males and rising. And of course they are appearing in leadership positions because they can lie directly and convincingly to far more people. (Mass media gave them a boost, but social media made them rocket-propelled.)

I checked, by the way. All four of the men listed above are daily, even hourly liars. They are male, fairly intelligent, and some people at least find them charming. They have all have five or more children (Johnson is at 7+), and all except Orban are currently on their third wives. Bingo!

But here’s the really interesting question: why are all these men now on their way out of power or already gone? That may be part of their sociopathy too, because they all leave trails of human wreckage behind them: cheated partners, abandoned lovers, betrayed followers. They can’t help it; it’s who they are.

So the good news may be that genuine sociopaths get found out in the end. The bad news, however, is that there’s lots more of them out there, and they’re breeding like flies.