Life Ain't Easy: What Would Make an Exoplanet "Earth-Like"? [Excerpt]
Two prominent scientists update our view of the history of life on Earth, featuring the prominent roles of oxygen and carbon dioxide, and question claims that it is fairly easy to initiate life—even on a planet such as ours
What May Become of Homo sapiens
Conditions of modern life could be driving changes in the makeup of our genes. Our bodies and our brains may not be the same as those of our descendants
The Future of Man—How Will Evolution Change Humans?
Contrary to popular belief, humans continue to evolve. Our bodies and brains are not the same as our ancestors' were—or as our descendants' will be
The Extinction of the Ammonites
Changes in the shells of these nautliuslike marine animals at the end of their long history suggest they were fighting a losing battle against more mobIle, shell-crushing predators
The Buoyancy of the Chambered Nautilus
The animal trims its weight and gains mobility by dividing its shell into compartments and removing their watery content. It succeeds in spite of the ocean's pressure, which tends to drive water back in