Some current theories focus on yawning as a social cue (like laughing) that communicates information and helps organize group behavior.

A century and a half of scientific inquiry has yet to solve this one.

Like many plants, most species of grass produce a bright pigment called chlorophyll.

The function of body and head hair, and why it grows the way it does.

Fecal matter, aka poop, is the end product of the digestive process - and here's the secret of its chief visual property.

A combination of calcium-rich casein and certain fats give bovine juice its color.

Actually, bare feet prevent these stately ice emperors from burning up in their suits.

An explanation of the purpose of melanin in humans and other animals.

An explanation of limb numbness and paresthesia.

Screaming is an evolutionarily useful tool becuase it lets others know something is wrong.

Don't get offended! You could be hyper-hygienic and you'd still ooze odors. Even grosser, bacteria's to blame.

It's clear that a human brain knows a good tune when it hears one.

When you pop the top, the pressure inside the can decreases, causing the CO2 to convert to gas and escape in bubbles.

Evolution seems to have allowed for varying types based at least in part on environmental pressures.

You'll never swim out to the horizon, and you'll never reach a rainbow's end. The visibility of both requires distance between object and observer.

Those external folds of cartilage and skin, called the pinna, have important resonant properties that modify high-frequency sound waves entering the ear before funneling them to the middle ear.

Beer likely dates back to the dawn of cereal agriculture.

The history of the public museum.

That ringing or buzzing in the ear is a symptom of hearing loss resulting from excessively loud noises.

Two competing theories are currently rolling around the academic journals for acceptance.

The Doppler effect describes the difference between a sound and its source.

Prometheus stole fire from the gods and bequeathed it to humans. Aristotle defined it as one of the four essential elements.

Amnesia can occur as a result of head trauma, drug toxicity, stroke, Alzheimer disease, infection or even emotional shock.

Determining which categories an organism falls into is no easy matter. In general, physical characteristics determine grouping.