Q: Why is it so hard to move your toes separately?

-Amelia T., Ohio

A: So you didn't write this question with your toes? Unfortunately, my toes can't type either. While determined people have taught themselves to light matches, open medicine bottles, play video games, knit, and perform all sorts of other handy feats with their, er, handy feet, most people can simply wiggle their toes a bit.

Humans' lack of foot dexterity is a worthwhile trade-off, says anatomy specialist Jeffrey Laitman.* It's the price of our two-legged gait. Human feet are literally made for walking. Our closest primate relatives, monkeys and apes, have longer toes and an opposable big toe that functions like our thumbs, allowing them to grasp things easily with their feet. Human feet were probably similar millions of years ago. Then, to accommodate an upright stance, our big toe rotated in line with the other toes. We lost some grasping ability. We also developed two specialized arches that efficiently bear our weight.

With practice, you can teach your toes new tricks. But, Laitman urges, don't wear high-heeled shoes: "It took evolution millions of years to create your foot. Do not destroy it with bad shoes!"

-Ruth

*Jeffrey Laitman is the Director of the Center for Anatomy and Functional Morphology at Mount Sinai School of Medicine in New York.

Q: Why can't a bird be electrocuted from sitting on a power line?

-Warren W., Idaho

A: "Some are," says University of Illinois electrical engineer George Gross. "Usually those with large wingspans."

Why large birds can get zapped but the little ones don't has to do with how electric current works. "Current tries to move through the path of least resistance," Gross notes. For the current to move off the wire and course into the bird is for it to go a long way around. A bird on a power line is essentially an unwelcome detour for the electrons on their path along the wire. Therefore, the bird's body remains an unexplored path for the current.

All that can change with shocking results, if the bird spreads its wings in the wrong direction. A large-winged bird can easily make contact between the wire it's sitting on and another wire, turning itself from detour to shortcut. "The circuit between the two wires provides a path for the electrons to escape through," notes Gross. "The bird's body is not able to withstand such a large current." So the same power line that's a chickadee's perch can be a condor's deadly high-wire act.

-Andy

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