Thousands of years ago, after domesticating cows and other ruminants, humans did something remarkable: They began to consume the milk from these animals.

But living closely with animals and drinking their milk also presents risks, chief among them the increased likelihood that infections will jump from animals to people. Some of humanity’s nastiest scourges, including smallpox and measles, probably originated in domesticated animals. In the 19th century, health authorities began pushing for milk to be treated by heating it; this simple practice of pasteurizing milk would come to be considered one of the great public-health triumphs of the modern era.

Today, however, a small but growing number of Americans prefer to drink their milk raw. And Robert F. Kennedy Jr., President Trump’s choice to lead the Department of Health and Human Services, now stands at the vanguard of this movement.

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