Every parent knows that a child's first step is a landmark event. It takes many months for that halting step to develop into a sturdy gait, but as toddlers become walkers, they open the door to independence, exploration, and, eventually, productivity. And just as walking is a signal achievement for each person, the two-footed upright gait is a banner accomplishment for our species. In fact, walking is one of the things that distinguishes man from all other animals.

Walking is an automatic, intrinsic human function, and it serves many practical roles. Strange as it seems, though, modern man appears determined ...

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In fiction, arsenic is best known as a poison; the metal is so notorious that it's been called the king of poisons. In fact, arsenic has been used by so many members of royal households that it's also been called the poison of kings. But arsenic is much more than a murderer's tool. In the past, it was used to treat a variety of illnesses, ranging from sleeping sickness and syphilis to psoriasis and leukemia. It was also used in many pesticides. And even though medicinal and agricultural uses of arsenic have been largely abandoned, the metal still has a ...

Medical memo Age and performance Whatever your politics, John McCain's energetic run for the presidency in 2008 shows that age is no barrier to success in the public arena. Still, it's impossible to deny that things change as men age. Among other things, reaction times, sensory-motor skills, and fine coordination tend to decline. At the same time, though, added years provide added experience.

Can experience, knowledge, and judgment compensate for subtle mental and motor changes? Two very different studies suggest that seniority does have its compensations.

Senior pilots The Federal Aviation Administration (FAA) requires all commercial airline pilots to retire ...

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Drug expiration dates Q. My husband subscribes to Harvard Men's Health Watch, but I read it and like it as much as he does. Since he listens to your advice, I hope you can resolve a problem that worries me. My husband refuses to throw out pills that are past their expiration dates. I never keep foods longer than I should, so I hope you'll convince him to clean out the medicine closet the way I take care of the fridge and pantry.

A. Your question poses a challenge to both diplomacy and science. Although there is relatively ...

I don't have allergies, but my eyes often burn and itch. My vision is fine, but my eyes are sometimes bloodshot, and I come down with two or three sties a year. I don't want to bother my doctor with such a minor problem, but I wonder if you can help.