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Human behavioral ecologist Alyssa Crittenden of the University of Nevada in Las Vegas has studied the Hadza since 2004.

What does research suggesting we should focus on diet, not exercise to lose weight and the evolutionary reason we sleep less as we age have in common?

Much like the weather, some human stomachs change throughout the year. The gut microbes of the Hadza, a hunter-gatherer group in Tanzania, shift dramatically as their diet changes with the seasons, according to new research from Stanford University. When applied on a longer timescale, these trends could explain why industrialized populations have a less diverse set of gut microbes and more chronic disease relative to hunter-gatherer populations.

A sound night’s sleep grows more elusive as people get older, but what some call insomnia may actually be an age-old survival mechanism.

Trouble sleeping is a common complaint among older folks, but what if their insomnia traces back to prehistoric times when Grandma and Grandpa were in charge of keeping the cave safe at night?

If your sleep is getting worse with age, evolution might be to blame. A study recently published in Proceedings of the Royal Society B found that humans' age-specific sleep patterns may have evolved to protect mixed-age groups from potential danger in the night. And in this scenario, the elderly members of these groups may have drawn the short straw—their restless sleep made them perfect for the night watch.

You may not look forward to sleeping less as you get older. But maybe it wouldn’t seem as bad if you knew it once played an important role in human survival.

Poor sleep is often regarded as a modern affliction linked to our sedentary lifestyles, electric lighting and smartphones on the bedside table.