What does science tell us about the right age for a leader? U.S. voters have been struggling with this question since Joe Biden and Bernie Sanders entered the pool of presidential candidates at the ages of 77 and 76. Either would surpass 72-year-old Donald Trump’s record as the oldest president to be elected to a first term.

These numbers have sent several pundits running for the actuarial tables, only to find that while average life expectancy at birth for American males is around 78 and a half, the numbers that apply to Sanders and Biden are conditional probabilities. Given that they’ve already reached their late 70s, their odds are now good for getting into their late 80s.

In last week’s Washington Post, Yale professor Jeffrey Sonnenfeld argued that there’s nothing wrong with a 70-something leader. To back this, he cited numerous examples of energetic leaders in their eighth and ninth decades.

Individuals have followed leaders since the dawn of humanity – or more likely, since long before: Many social animals, such as elephants, follow leaders, said Mark van Vugt, an evolutionary psychologist and author of the book “Naturally Selected: The Evolutionary Science of Leadership.” When it comes to leadership, elephants pick the oldest female, he said, which works to the whole herd’s advantage because elephants really do depend on their memories, and older elephants have more accumulated useful knowledge, such as the location of the best migration paths and good watering holes.

For people, the long-term pattern is similar, but a little more complex, said van Vugt. In what he calls small-scale societies – what people lived in for most of human existence – people followed the guidance of elders in their 60s and 70s in times of stability and young men in times of war. The older people had experience and skill in solving conflicts, and back before Twitter, they had more useful social contacts than younger people did.

There are vestiges of this in recent history. While U.S. presidents tend to cluster in their 40s, 50s and 60s, leaders of revolutions have been much younger – Fidel Castro, 33; Napoleon, 30; and Emiliano Zapata, 31. (Something similar happens with CEOs: Those who head Fortune 500 companies average around 50, but Silicon Valley entrepreneurs starting new companies average around 30.)

This doesn’t necessarily mean youthful leaders create revolutions. It may be that when enough citizens want a revolution, they turn to the young.

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To test whether conditions change age preferences, van Vugt and colleagues conducted an experiment, in which they showed subjects pictures of young and older faces and asked them who they’d want as a leader under different circumstances. When told things were stable, they chose the older faces. When told society was in the middle of a big transition in its economy or technology, they chose the younger ones. (Indeed, older leaders are often mocked for lack of tech savvy – as when columnist Richard Cohen suggested that Biden probably thought Snapchat was a cereal.)

Is there any rationality to people’s preference for older leaders in some circumstances and younger ones in others? It might have been a pretty good heuristic in small hunter-gatherer groups. But today, a better guide would be candidates’ stands on policy issues. If the oldest candidate has the best ideas to navigate a dynamic moment in the nation’s evolution, then great – that candidate is the best choice, regardless of stereotypes about age.

There are other ways we are stuck in the Stone Age when picking leaders. In those small societies, van Vugt said, the leader’s decisions meant life or death – go right or left, pick this or that new hunting ground, fight with the hostile neighbors or retreat. And so, with that habitual thinking pattern, we still tend to assume presidents and CEOs are responsible for every up and down of an economy or a company’s bottom line. Our brains, geared as they are for a different world, give leaders too much credit for fortune and too much blame for its reversal.

Humans are also particularly ill-adapted to television and video, which give us the illusion that we know potential leaders personally, the way our ancestors did in those small-scale societies. People who watch more television are more likely to make their political choices based on appearance, including whether the person looks old or young. Those who see less footage focus less on the looks of a candidate and more on the policy.

There is evidence the average person loses some mental capacities by 70 or so, most of this amounting to loss in speed; they can still do everything younger people can do, but a little slower. That kind of speed may not matter much outside the heat of battle. And a factoid about “the average person” doesn’t mean any given individual is any less sharp at 77 than at 50. So if science has anything to tell us about age and leadership, it’s that we should not to let it distract us from things that matter – such as policy.

Faye Flam is a Bloomberg Opinion columnist. She has written for the Economist, the New York Times, the Washington Post, Psychology Today, Science and other publications. She has a degree in geophysics from the California Institute of Technology.