February 25, 2016 6:55 AM EST

Studies have shown that eating too much meat can lead to heart disease, among other conditions. But if that’s the case, why did humans evolve to be carnivorous in the first place? The answer, according to science journalist Marta Zaraska, is that we (kind of) didn’t; rather, we evolved because we ate meat. Prehumans had a mostly plant-based diet, comprising fruits, leaves and flowers. But some 2.5 million years ago, climate change caused lengthy dry spells over the African savanna, severely limiting many of those calorie sources–and making lions’ leftovers, like zebra meat, an appealing alternative (with extra nutrients that helped our brains grow). By 1.8 million years ago, we were hunting game on our own, fostering the kind of teamwork and communication that allowed us to have complex social lives. That know-how also allowed humans to move to continents with less abundant edible plants, which helped our species spread. Today most people don’t need meat to survive; there are plenty of nutrient-rich, plant-based foods available. But our taste buds, Zaraska writes, “obviously didn’t get the memo.”

This appears in the March 07, 2016 issue of TIME.

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