5 Most Incredible Discoveries of the Week

A famous conqueror's assist from Mother Nature and an intriguing "hell diamond" from deep in the Earth are on the list :

• Genghis Khan Owes His Empire to … Rain: Turns out, Genghis Khan had a secret weapon that helped him create his empire in the 13th century. Tree-ring scientists have discovered that central Mongolia had an usually warm and wet spell from 1211 to 1225, which coincides with Khan's rise to power. That climate created lush grasslands that fueled his horse-driven army.
• ‘Hell Diamond’ Signals Vast, Deep Water Deposit: A huge "wet zone" hundreds of miles beneath the surface of the Earth could hold as much water as all the oceans put together, according to researchers analyzing a mineral from deep in the mantle. The water is "not a Jules Verne-style ocean you can sail a boat on," explains one, but is held inside minerals in the "transition zone" 250 to 400 miles underground. One theory: It arrived long ago via asteroids or comets.
• Elephants Can Recognize Different Human Languages: Speak the wrong language in front of an African elephant, and she may not like you much. In a study at a Kenyan national park, researchers played recordings of different languages and voices for 47 elephant family groups, and found that the animals got defensive only when hearing the sounds of Maasai men, whose cattle-herding can cause run-ins with elephants.
• Ancestor of All Animals: the Sponge? Sea sponges don't get much respect—or even much use as sponges any more—but humans and every other complex animal on the planet may owe our existence to them, according to new research. Scientists believe primitive versions of the filter-feeders, which can survive in water with very low oxygen, helped oxygenate the deep seas by consuming organic matter, creating conditions ideal for other life forms to evolve. Sponges, then, are a good candidate to be the "Animal Eve" from which all today's creatures evolved.
• Researchers on Horseback Find Bits of 1765 Shipwreck: In a tale of archaeology with a bit of an Indiana Jones ring to it, researchers have identified new pieces of a 1765 shipwreck off Argentina—while traveling 125 miles of Tierra del Fuego on horseback. They even think they know where the ship went down off the coast, but they're keeping it a secret to deter scavengers.

Click for more discoveries, including one that suggests the Bronze Age had hipsters, too. (More discoveries stories.)