Paul Ehrlich and me

Stanford biologist Paul Ehrlich died on March 13th. His 1968 book “The Population Bomb” was both influential and controversial in its time and has proven to be better fiction than science since then. I was required to read The Population Bomb in college. I recall being beguiled by its arguments and probably too by the stature of its author. Over the decades, I’ve come to appreciate the value of prophecies like those of Ehrlich; they are specific enough that, if we live long enough, we can see if they come to pass. If they do, the prophet is validated. If they don’t, he is discredited.

In the case of Ehrlich, he was massively and conclusively discredited by events that followed.

“. . . in 1970 he forecast that within the coming decade “100-200 million people per year will be starving to death” and “by 1985 enough millions will have died to reduce the earth’s population to some acceptable level, like 1.5 billion people”. Furthermore, by 1980 the life expectancy of the average American would have fallen 42 years as a result of cancer caused by pesticides.

“. . . he lived to be one of more than 8 billion people in a world where global life expectancy has increased at the average rate of seven hours per day since he forecast it would collapse. Meanwhile, famine has all but gone extinct, with death rates from mass starvation down to a tiny fraction of what they were in the 1960s. Here are the astounding numbers: in the 1960s, 29.7 million people out of a population of 3 billion died in famines that killed more than 100,000 people each. In the 2010s, 1.1 million out of a population of more than 8 billion died in such episodes: a decline of 99% in the death rate.”

Look, I’m a scientist. Science is in the prophecy business. If you really understand mechanism, you can predict outcomes from initial conditions. And prophecy is what people pay money for.

Of course, science is also self-correcting. When confronted with new evidence, we revise our conclusions. At least for most scientists, though not apparently for Ehrich:

“For the rest of his life Ehrlich remained adamant that he was not so much wrong as…right. In 2008 he was still predicting “an unhappy increase in the death rate”. In 2023 he tweeted plaintively: “If I’m always wrong so is science, since my work is always peer-reviewed, including the POPULATION BOMB and I’ve gotten virtually every scientific honor. Sure I’ve made some mistakes, but no basic ones.”

I’ve lived long enough to see many paradigms overturned or replaced when new data emerge. Science isn’t religious dogma, and every scientific conclusion is provisional. But science is also a business, and some scientists succumb to the temptation to confuse their celebrity for truth. History will place Ehrich in the same pantheon as Lysenko.

The problematic legacy of Paul Ehrlich