Tamyra Ames describes her oldest son as a “heart attack waiting to happen.”

When Luke was only 18 months old, he climbed out of bed, unlocked the door, opened the gate and toddled into the street.

Six months later, he sneaked through a sliding door and climbed into the pool. When he was 8, he pushed through the screen and tumbled out a second-story window, surviving with minor bruises.

Her twins, Kathryn and Jason, were even worse, thwarting every baby-proofing device that she bought, says Ames, of Tucson. They greedily gobbled the dog food and even boosted each other over the baby gate.

“Toddlers are so excited by the world, and they’re experimenting all the time,” says pediatrician Harvey Karp, who describes toddlers as “little cavemen” in his book, TheHappiest Toddler on the Block (Bantam, $15). “But their abilities leap ahead of their judgment and their ability to think things through.”

After a day spent rescuing their young daredevils from self-destruction, experts say parents can’t be blamed for wondering: How on earth has the human race survived? If natural selection promotes the survival of the fittest, shouldn’t that process have chosen less dangerous tendencies in the smallest, softest and most clueless of humans?

A different kind of danger long ago

In fact, these common childhood behaviors may have been less hazardous in humanity’s early days, says Joyce Benenson, a biological anthropologist at Harvard University.

She notes that the typical baby’s environment has changed radically since the days of hunting and gathering.

In the few remaining hunter-gatherer cultures, women carry their children in slings for their first few years of life, nursing them through the wildest days of toddlerhood. That keeps babies from running off or putting dangerous objects in their mouths, Benenson says. Extended families and neighbors in these cultures help parents keep a close eye on children.

“These horribly dangerous behaviors just wouldn’t have had a chance to hurt too many of us,” Benenson says.

Though the natural world presents hazards of its own, babies who graduated from the maternal sling may have had fewer opportunities for mischief than toddlers today, says Meredith Small, an anthropology professor at Cornell University in Ithaca, N.Y., and author of Our Babies, Ourselves.

“Our homes have more stuff that can be a danger to kids,” Small says.

In humanity’s early days, babies were more vulnerable to the elements and diseases that are now easily treated. But there were no toys with small, detachable parts, no plastic wrap in which babies could suffocate, no windows blinds with dangling cords, no caustic cleaning supplies.

Some toddler behavior may reflect evolution at work. Babies’ tastes — such as a marked preference for sweets and fats — also may have protected them through the ages, Small says.

  • That sweet tooth encourages babies to seek out ripe fruits and calorie-rich foods, such as breast milk, but avoid poisonous plants, which tend to taste bitter, Small says. Those preferences may have protected babies playing on the forest floor, even if they frustrate modern parents trying to get toddlers to eat their greens.
  • Gumming everything in sight — including muddy rocks and twigs — may offer babies hidden advantages, such as extra iron or other nutrients from the soil, Karp says.
  • Mouthing objects also may help build a baby’s immune system by exposing them to tiny doses of local germs, making them better able to fight off seriousinfections, says William Schaffner, an infectious-disease expert at Vanderbilt University.

Why teens don’t sleep like babies

Early tribal life may even have shaped how modern children sleep, says anthropologist Carol Worthman, director of the Laboratory for Comparative Human Biology at Emory University in Atlanta.

Babies wake up at dawn, she notes, but many teenagers prefer to sleep until noon. Those internal alarm clocks may have evolved to safeguard the tribe, Worthman says.

Because babies and old people are the weakest members of a community, it makes sense for them to be still at night, Worthman says. Teens and young adults, with their sharp eyes and quick reflexes, are better equipped for the night shift.

Karp says he has come to appreciate childish behavior, even though it can be exhausting for parents:

“There’s no question that our race has evolved and our culture has matured because of our ability to think of things different, to be inventive and innovative in our thinking and test things out.”

READERS: Go ahead, tell us about the cute and crazy things your toddlers do or did! Share stories of “little cavemen” moments and advice on baby-proofing and keeping kids safe below.

Written by Liz Szabo, posted on 3/3/2009 at www.usatoday.com