Over the past 50 million years, a group of small, hoofed mammals gradually evolved into today’s whales and dolphins. In the process, they gained much: a watery, planet-wide habitat and bountiful sources of food. But they lost a lot, too. Surrounded by endless blue, they became color-blind. Immersed in water, their sense of smell disappeared. And for some reason, they lost a gene called PON1.
PON1 helps humans and other mammals process fatty acids and cholesterol, but whales—and other marine mammals like manatees and seals—seem to have lost the need for it. For most of their existence, the gene’s absence was inconsequential.
Not anymore.
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Today, organophosphates are widely used as pesticides, and they occasionally become environmental pollutants. And as it happens, our main defense against these chemicals is a gene that can break them down—PON1, the same gene that whales have lost.
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For millions of years, the loss of PON1 was just another quirk of evolution. Now it’s a tragic vulnerability. It means that whales and other marine mammals are uniquely susceptible to toxins that have only existed for a few decades.
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“People have the impression that mammals are only susceptible to these pesticides at high levels, but marine mammals might be susceptible at low levels,” [researcher Wynn] Meyer says. “We need data on how much these compounds are getting into the environment and accumulating in the animals.”
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