Thousands of dead fish have begun mysteriously washing up in the polluted Rio bay that will host sailing events at the 2016 Olympics -- and experts are at a loss to explain why.

Guanabara Bay has already been the subject of concern amongst sailors who are to compete in Rio because of the human sewage that gets pumped into its waters.

For millennia, the sight of a comet filled humans with awe or dread.

The birth of Jesus, the assassination of Julius Caesar, the Great Plague of London, the coming of war or peace, bountiful harvests or famine... all thought to be portended by cosmic herald.

DNA recovered from the fossilized leg bone of a man who lived 36,000 years ago suggests early Europeans survived the Ice Age, researchers said Thursday.

The international team of scientists also said the DNA from one of the oldest known anatomically modern humans shows that interbreeding with Neanderthals took place some 54,000 years ago, far earlier than previously thought.

The human populations now predominant in Eurasia and East Asia probably split between 36,200 and 45,000 years ago, according to a study released Thursday.

Researchers used new techniques to analyze genetic samples from the shin bone of a young man who died at least 36,200 years ago near Kostenki-Borshchevo in what is now western Russia. The study, published in the journal Science, concludes that Kostenki man shared genetic sequences with contemporary Europeans, but not East Asians.

The space tourism company that suffered a tragic setback when its experimental rocket-powered spaceship broke apart over the California desert could resume test flights as early as next summer if it can finish building a replacement craft, its CEO said Wednesday.

The sleek composite shell and tail section of the new craft are sitting inside the company's manufacturing facility in Mojave, California.

Scientists have discovered a new species of deep-sea coral in underwater canyons off the Northern California coast, the National Oceanic and Atmospheric Administration announced Wednesday.

A NOAA research team using small submersibles found the coral in September near national marine sanctuaries off the coast of Sonoma County, the agency said.

Chinese diplomatic and military staff went on buying sprees for illegal ivory while on official visits to East Africa, sending prices soaring, an environmental activist group said Thursday.

Tens of thousands of elephants are estimated to be slaughtered in Africa each year to feed rising Asian demand for ivory products, mostly from China, the continent's biggest trading partner.

Until a few decades ago, there were no beavers in Patagonia. That changed when 20 pairs of the tree-chewing creature were introduced with the hopes of creating a fur industry.

Today, their numbers have exploded and they pose a serious threat to the South American area's biodiversity.

As slow-moving lava approached a cemetery in a rural Hawaii town, Aiko Sato placed flowers at the headstone of the family plot she's tended to over the years, thinking it would be the last time she would see it.

"I made peace with myself," Sato said Monday of visiting the Pahoa Japanese Cemetery on Oct. 23. A few days later, lava smothered part of the cemetery and the family believed the headstone had been buried.

Small islands, long thought to be natural tsunami barriers for coast-dwellers, may in fact amplify the waves they are supposed to break, researchers warned Wednesday.

The findings are of concern, for many coastal communities have settled in areas traditionally believed to be shielded from waves by offshore islands.