A 375 million-year-old fossil has shed new light on the theory of evolution, challenging the widespread view that large hind appendages first appeared after vertebrates transitioned from the water to land.

A report published in the Proceedings of the National Academy of Sciences said the well-preserved pelves and partial pelvic fin of a Tiktaalik roseae -- which looked like a cross between a crocodile and a fish -- indicated that hind legs actually began as hind fins.

Inspired by nature and by the aviation pioneers of the early 20th century, scientists in the United States said Wednesday they had built the world's first jellyfish aircraft.

The tiny, ultra-light lab machine, weighing just 2.1 grams (0.07 ounces), is the first man-made flying object to hover and move with a motion like that of the jellyfish in water, the inventors believe.

A scientist published a guide Wednesday to help authorities limit deaths from fallout after a city is hit by a nuclear bomb.

Taking cover in existing buildings is widely accepted as a critical first action after a nuclear blast in a major city.

Indonesia's Mount Sinabung erupted more than 30 times Tuesday spewing lava and ash clouds over a wide area, officials said, with more than 26,000 people now forced to flee their homes.

Sinabung, which lies in the northwest of Indonesia's Sumatra island, sent hot rocks and ash 5 kilometers (3.1 miles) into in the air, spreading hot clouds over a 4.5 kilometers radius, the Center for Volcanology and Geological Hazard Mitigation told Agence France Presse.

Are people with kids happier than people without? In the United States, those with and without kids rate their lives about the same, but globally children tend to diminish well-being, said a study Monday.

The results were derived from two major surveys by Gallup that included almost three million people worldwide.

A plant thief has stolen one of the few surviving examples of the world's smallest water lily, which is extinct in the wild, from the Royal Botanic Gardens at Kew in London, police said.

The tiny 'Nymphaea Thermarum' was stolen on Thursday from the Princess of Wales Conservatory, a giant glass house at the gardens in the southwest of the capital, a Scotland Yard statement said.

Energy-related carbon dioxide pollution grew by 2 percent last year after declining several years in a row, a government report said Monday. The increase was largely due to a small boost in coal consumption by the electric power industry, according to the study by the U.S. Energy Information Administration.

American cars and factories spewed 5.38 billion tons of carbon dioxide in 2013, up from 5.27 billion in 2012, the report said. Carbon dioxide is the chief man-made global warming gas.

Antarctica's Pine Island Glacier, one of the biggest single contributors to world sea-level rise, is melting irreversibly and could add as much as a centimeter (0.4 inches) to ocean levels in 20 years, a study said Sunday.

The glacier "has started a phase of self-sustained retreat and will irreversibly continue its decline," said Gael Durand, a glaciologist with France's Grenoble Alps University.

Bulging in land that occurs before a volcano erupts points to how much ash will be spewed into the sky, providing a useful early warning for aviation, geologists in Iceland said on Sunday.

The telltale came from data from Global Positioning System (GPS) sensors placed around the notorious Icelandic volcano Grimsvoetn, they said.

Authorities in Uruguay on Sunday recovered the body of a 16-meter sperm whale, normally at home in deep waters, after it beached near the capital.

Using a crane, the authorities moved the animal from the shallow waters onto the beach off Carrasco, an upscale town just next to Montevideo.