Engines of Our Ingenuity

No. 618:
BLACK SALT

by John H. Lienhard

Click here for audio of Episode 618.

Today, a fable of death by racial superiority. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Black Americans are horribly at risk of hypertension. Half of Black American males are hypertensive when they reach 50. Ten times as many die of hypertension as do Whites. Kidney disease is 18 times as common among Blacks as it is among Whites. Diabetes also hits Blacks much harder.

Dr. Jared Diamond suggests a startling reason for this imbalance. He invites us into the West African bush in, say, 1800. Slavers capture 100 Africans. They put them in chains and march them 800 miles to a coastal port. They load them down with their supplies. They give them little water or food. Twenty-five die of exhaustion in the month-long trip. Nine more die of heat and dehydration in a coastal holding cage.

Only 66 live to cross the ocean, chained in their own filth in the hold. Seven more die of diarrhea, heat, and scurvy on the way. Three die waiting to be sold. Then another 16 die of heat exhaustion and bad diet during the first three years on the plantation.

By now forty -- maybe fewer -- have survived. They've made it because they could adapt to a diet with hardly any salt. The Darwinian selection process has created a race of super body-salt savers. The survivors also have remarkable sugar metabolism to sustain them through starvation.

The survivors of slavery have other natural advantages. One dramatizes our point today. It's a resistance to malaria. Sickle cell hemoglobin gives that resistance. But when people protected by the sickle cell trait marry, one in every four of their children suffers sickle cell anemia.

So the blessing becomes a curse. Black Americans emerge with a huge Darwinian advantage. But the advantage turns to a death sentence, now that we load our diets with salt and sugar.

All this creates a hard moral fable in a world that loves specialization. The best survivors are not specialized. They're people who can adapt to varying conditions. Sooner or later it works against us to become a specialized superman.

Today, Black Americans come into their own in a land that hasn't treated them well. As they do, it is an eerie fact that the hard-bought ability to live on a low-salt, low-sugar diet turns to disadvantage. I ask anyone who believes in racial superiority to look at the damage this Black superiority has done.

In the end, the only real edge is adaptability. And that's a human trait, not a racial one.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


Diamond, J., The Saltshaker's Curse. Natural History, October, 1991, pp. 20-26.


The Engines of Our Ingenuity is Copyright © 1988-1997 by John H. Lienhard.

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