For most of the Earth's history, life consisted of the simplest organisms; but then something happened that would give rise to staggering diversity, and, ultimately, life as complex as that which we see today. Scientists are still struggling to figure out just what that was.
The human eye is an amazing mechanism, able to detect anywhere from a few photons to a few quadrillion, or switch focus from the screen in front of you to the distant horizon in a third of a second. How did these complex structures evolve? Joshua Harvey details the 500 million year story of the human eye.
Lake St. Lucia, Africa's largest estuary lake, is under siege. A series of human missteps have left it cut off from the sea, and the water levels are dangerously low. The wildlife relying on its ecosystem are most affected--from hippos and crocodiles that live on its banks, to exotic birds that migrate from as far as 6,000 miles away. Can they adjust to the new, drier reality imposed on them?