Why Aren’t (Most) Humans Furry?

Ever since Darwin first made headlines, scientists have been pondering why humans lost their natural coats as they evolved from apes. The theories range from lice to cannibalism.

The traditional theory—refined by scientists over the past 40 years—proposes that humans gradually became furless in order to withstand the brutal heat of the African savanna or to prevent over heating while chasing prey. One alternative idea, put forth in 2003 by evolutionary biologist Mark Pagel of the University of Reading in England, is that as humans learned to keep warm by making clothing and building shelters, they no longer needed heavy body hair. This hairlessness prevented parasites, such as mites and ticks, from sticking to their bodies. Avoiding parasites led to healthier humans, Pagel posits, and because there’s nothing as attractive as a bug-free hominid, hairlessness became a desirable feature in a mate, and natural selection drove the hairier folks into extinction.

In 2006, developmental psychologist Judith Rich Harris suggested a far more gruesome mechanism. As humans became hairless as a result of chance mutations, they split geographically from their hairy cousins. Once hairlessness was in style, any hirsute baby born to a hairless tribe was abandoned. As hairlessness became the norm, a thick fur coat would have become so rare that hairy humans would have been seen as animals and hunted for food. The days before waxing were savage indeed.

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How Will the Universe End?

In 1929, Edwin Hubble discovered that the universe is not in fact static, but expanding. In the years following his discovery, cosmologists took up the implications of the discovery, asking how long the universe had been expanding, what forces caused the expansion, and whether it will ever cease. Cosmologists are pretty confident about the first question: just shy of 14 billion years. A great deal of evidence supports the predominant answer to the second question: The universe rapidly emerged from a singularity in an event that cosmologists call the Big Bang. The third question is a bit more mysterious, and the answer relies on an obscure, confounding phenomenon known as dark energy. The density of dark energy in the universe determines its ultimate fate. In one scenario, the universe does not possess enough dark energy to forever counteract its own gravity and thus ends in a “Big Crunch.” Under this scenario, the universe’s gravity will overcome its expansio...

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Why Do We Have Fingerprints?

Many scientists once thought fingerprints help us hold onto objects. From an evolutionary perspective, getting a better grip on tools or weapons would have made life easier for early humans. In 2009, Dr. Roland Ennos of Manchester University designed an experiment that tested the gripping power of our fingerprints. He used a machine equipped with weights to pull strips of Perspex, a kind of acrylic, across a subject’s fingertips. The machine measured the amount of friction created as the acrylic passed over the tip. In the real world, a high amount of friction between two solid objects in contact with each other would indicate a better grip. In the experiment, the fingertips created some friction on the acrylic, but not as much as Ennos had expected. Ennos compares our fingerprints to the tires on a race car. Ridges in the tire reduce the surface area of the tire in contact with the road, which reduces friction. The ridges on fingertips have the ...

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