Here’s a thought that has occurred to a lot of weight-conscious people: If fatty, salty foods are so bad for us, why do we crave them? Shouldn’t our bodies, evolving over many millennia, naturally want to eat foods that are good for us?

Cardiologist Lee Goldman examines this paradox in a larger context in his new book, “Too Much of a Good Thing: How Four Key Traits Are Now Killing Us.” He goes beyond diet issues to talk about survival mechanisms that worked well for thousands of generations but have now turned against human health:

● A craving for high-calorie foods and the ability to store excess calories as fat: These traits helped our ancestors survive when food was scarce; today, he says, they explain why so many Americans are dangerously overweight or obese.

● A craving for salt: Early man continually faced the possibility of fatal dehydration, so human bodies evolved to crave and conserve both water and salt. Today our heavy consumption of salt, combined with the internal hormones that conserve salt and water, contributes to heart disease, stroke and kidney failure.

● Fear and self-protection: Hypervigilance enabled our ancestors to escape or defeat a variety of prehistoric dangers. Today this impulse contributes to soaring rates of depression, anxiety, post-traumatic stress disorder and suicide.

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● The ability to form blood clots: Before the advent of medical care, humans’ efficient clotting mechanism kept people from bleeding to death after injuries, and particularly after giving birth. Today the same clotting mechanism contributes to heart attacks and strokes, the leading causes of death in today’s industrialized societies.

In all, writes Goldman, dean of the faculties of health sciences and medicine at Columbia University Medical Center, these four traits have evolved to the point where they cause more than six times the number of deaths they prevent.

Beginning with a chapter titled “Can our genes evolve fast enough to solve our problems?” (short answer: no), Goldman discusses how we should think about correcting this paradox. He unsurprisingly advocates behavioral changes but also puts a lot of faith in medications and such genetic interventions as DNA repair and gene therapy. Eventually, he says, “the challenge is to use our brains, which so rapidly changed our environment and created these problems in the first place, to help us get back into sync.”