I once made the mistake--in the presence of a nun--of declaring that I was sweating.

She was quick to correct me; "No Caveman. Horses sweat, men perspire, and women glow." Irish wisdom, I believe.

As naked apes, we sweat like pigs. Even pigs and horses--the famous sweaters of the animal world--aspire to the sheer volume of sweat coming out of the human body on a regular basis. Our skin is covered in pores and loaded with sweat glands.

Considering that our primary method of temperature regulation is by sweating or not sweating, and that when the environmental temperature is high and we are active we sweat more, it stands to reason that this water-costly method would have only been possible if water was abundant throughout our evolutionary history.

We could have kept our hair and saved ourselves a LOT of water. Chimps have a fraction of our sweat glands per inch of skin.

Today, we live in climate-controlled environments, for the most part, and we could suggest that because we need to do less sweating, we need less water. Maybe, and undoubtedly we must consume a minimum amount to keep the body from panic and costly conservation, and undoubtedly must consume more water as fully dressed construction workers in the 100 degrees, than a policy analyst working in an office building and with air conditioning in his car.

As for the 8-glasses-per-day rule: it seems that much scientific brainpower is being spent trying to debunk an old-wives' tale. The tale was reinforced by dieters who put a premium on filling up with water so as to give them a full feeling that would decrease their appetite. Some have posed that extra water flushes out fat or toxins or whatever, without much evidence to support these theories. The smart dieter recognizes that human metabolism works efficiently when the body is adequately hydrated.

To specify a minimum amount of water consumed per day might be wise, but any sort of hard and fast rule is confounded by so many environmental variables that we're better off letting thirst be our guide. With so many new beverages available to moderns, can we trust our thirst? Maybe what we think is thirst is just our bodies' cheap way of getting more caffeine or sugar or alcohol.

Dehydration is panic mode, and makes us do things like spend the afternoon in shallow pits to conserve energy, or at the very least, slow down and want to spend the afternoon indoors on an otherwise beautiful day.