No one knows for sure why we sleep.

Hair and nails DO NOT continue to grow after a person dies.

The harder you concentrate, the less you blink.

You blink about 6 times a minute while reading.

Human kidneys weigh about 5 oz.

The average person sheds a layer of skin every 28 days (just not in one big piece).

Some studies show that a 30 minute nap each day can reduce the risk of heart attack by 30%.

There is no genetic cause of left-handedness; it is not an inherited trait. Statistically, a child is more likely to be left handed if:
the child is male,
the child is one of a pair of twins (although it is rare for both to be lefties),
the child is born to a mother with diabetes, or who is a smoker, or who is over 30.

Compared with right-handed people, left-handed people are:
at least twice as likely to be admitted to mental institutions,
three times as likely to be alcoholic,
four times as likely to have an accident resulting in an emergency room visit,
more likely to have an IQ over 140,
more likely to have an IQ under 70
more likely to have dyslexia.

Baldness is not caused by hair falling out. All hair stops growing and falls out after a period of time. Even if a person does not cut his scalp hair, each hair will only grow to a limited length before falling out. Every person with a full head of hair loses about 100 scalp hairs a day this way. If the hair is not replaced by a new hair growing in the same follicle, then "thinning" hair and eventual baldness result.

The pupil of a person’s eye dilates about 45 percent when the person is viewing something pleasant.

The human brain is pink, not gray.

There are about ten trillion cells in the human body.

The average person’s skin weighs about six pounds.

When a person dies, the first sense to be lost is sight. Then follow taste, smell and touch. The last sense lost is hearing.

A person who has a heart attack while exercising has a significantly greater chance of surviving than a person who has one while resting. This may be because those who require strenuous activity to bring on an attack have healthier hearts anyway; if rest can cause an attack, your heart probably is in poor shape.

The soles of your feet and palms of your hands contain more sweat glands than any other part of your body.

Human taste buds are less sensitive at higher altitudes.

A human brain is 80 percent water; it contains a greater proportion of water than does the blood

In 1977, a 13-year-old boy discovered a tooth growing on his left foot.

The gene for six digits is rare, but genetically dominant in humans; if you have the gene, you will have six fingers on each hand.

Your heart does NOT really stop when you sneeze (a sneeze takes much less time than a heartbeat).

Red blood cells contain no nucleus when they mature (although they start with one). They are the only cells in the body without one.

The average person is about a quarter of an inch taller at night.

Your pupils dilate when you see someone you love. They also dilate when you see someone you hate.

Rigor mortis occurs more rapidly if a person is killed in a fight or while under stress.

The typical human body has 70,000 miles of blood vessels.

Alcohol lowers the body’s temperature, but causes dilation of the capillaries which creates the illusion of warmth.

Normally, an autonomic reflex shuts a person's eyes when he sneezes. It is therefore nearly impossible for a person to keep his eyes open during a sneeze without external aid. However, a sneeze that occurs when eyelids are propped open will not result in the eyeballs popping out.

A normal, healthy person will never sneeze in his sleep. 

One of the symptoms of asthma is improved hearing.

Research has shown that beer tastes differently if the drinker hears a particular musical tone while drinking it. The tone for optimum taste is different for different beers.

Air expelled during a sneeze travels at about 100 miles per hour.

An average person laughs about 15 times a day.

Tongue prints are as unique as fingerprints.

Men without hair on their chests are more likely to have cirrhosis of the liver than are hairy-chested men. Gradual loss of chest hair and armpit hair is a symptom of cirrhosis.

Women are 37% more likely to go to a psychiatrist than men are.

People with blue eyes are the most sensitive to light. People with dark brown eyes are the least sensitive.

Your left lung takes in less air than your right one does.

Men's hearts beat slower than women's.

Younger women give birth to a larger proportion of boys than do older women.

Adults are more susceptible to death when bitten by a snake than a child is.

The brain uses 25% of the body’s oxygen, even though it comprises only two percent of the body’s weight.

The Neanderthal's brain was bigger than yours is.

A typical person’s mouth produces a quart of saliva a day.