All animals do the same thing to the food they eat — they break it down to extract fuel and building blocks for growing new tissue. But the metabolism of one species may be profoundly different from another’s. A sloth will generate just enough energy to hang from a tree, for example, while some birds can convert their food into a flight from Alaska to New Zealand.

For decades, scientists have wondered how our metabolism compares to that of other species. It’s been a hard question to tackle, because metabolism is complicated — something that anyone who’s stared at a textbook diagram knows all too well. As we break down our food, we produce thousands of small molecules, some of which we flush out of our bodies and some of which we depend on for our survival.

Continue reading “Stronger Brains, Weaker Bodies” →

Just a few centuries ago, Madagascar was home to a monstrous creature called the elephant bird. It towered as high as nine feet. Weighing as much as 600 pounds, it was the heaviest bird known to science. You’d need 160 chicken eggs to equal the volume of a single elephant bird egg.

The only feature of the elephant bird that wasn’t gigantic was its wings, which were useless, shriveled arms. Instead of flying, the elephant bird kept its head down much of the time, grazing on plants.

Scientists aren’t precisely sure when this strange creature became extinct, but it probably endured well into our human-dominated age.

Continue reading “A Theory on How Flightless Birds Spread Across the World: They Flew There” →