An arched fossilized foot bone found in Ethiopia shows that human ancestors walked upright 3.2 million years ago and were no longer tree dwellers, said a study Thursday in the journal Science.

The bone belongs to a cohort of the famed hominid Lucy, whose species Australopithecus afarensis roamed eastern Africa, and is the first evidence to address the question of how they got around.

Toddlers who have a diet high in processed foods may have a slightly lower IQ in later life, according to a British study described as the biggest research of its kind.

The conclusion, published on Monday, comes from a long-term investigation into 14,000 people born in western England in 1991 and 1992 whose health and well-being were monitored at the ages of three, four, seven and eight and a half.

People who are genetically predisposed to produce lower amounts of a certain brain chemical that regulates appetite and stress may be at higher risk of severe depression, researchers said Monday.

The findings should shed more light on how depression affects certain people more than others, and could help lead the way toward developing more individualized therapies, researchers at the University of Michigan said.

A survey of oyster habitats around the world released Thursday found that the succulent mollusks are disappearing fast and 85 percent of their reefs have been lost due to disease and over-harvesting.

Most of the remaining wild oysters in the world, or about 75 percent, can be found in five locations in North America, said the study published in BioScience, the journal of the American Institute of Biological Sciences.

Japanese researchers have collected eel eggs from the wild for the first time ever, shedding light on the mystery surrounding the spawning habits of the fish.

Experts say the new discoveries about how and where eels lay their eggs could help pave the way for new techniques to farm a creature that Greek philosopher Aristotle believed emerged spontaneously from mud.

Brazil's environmental agency announced Tuesday the "largest orchid in the world" was growing in a botanic garden in the capital, at a height of 8.2 feet (2.5 meters) and some stems measuring as long as 9.8 feet (three meters).

Displayed at the Brazilian Orchids Project garden in Brasilia, the flower -- part of the Grammatophyllum genus -- has been growing for five years and already has 19 long stems, on which 400 flowers bloom, said the Brazilian Institute of Environment and Renewable Natural Resources (IBAMA).

Modern humans may have left Africa thousands of years earlier than previously thought, turning right and heading across the Red Sea into Arabia rather than following the Nile to a northern exit, an international team of researchers says.

Stone tools discovered in the United Arab Emirates indicate the presence of modern humans between 100,000 and 125,000 years ago, the researchers report in Friday's edition of the journal Science.

Astronomers on Wednesday said they had snared an image of what may be the oldest galaxy ever seen, a starry cluster that came into being when the Universe was still a baby.

The tiny smudge of light captured by the orbiting Hubble telescope took 13.2 thousand million years to reach Earth, which means the galaxy was born some 480 million years after the "Big Bang" that created the cosmos.

Orangutans are far more genetically diverse than thought, a finding that could help their survival, say scientists delivering their first full DNA analysis of the critically-endangered ape.

The study, published Thursday in the science journal Nature, also reveals that the orangutan -- "the man of the forest" -- has hardly evolved over the last 15 million years, in sharp contrast to Homo sapiens and

U.S. doctors are treating soldiers suffering from post-traumatic stress disorder by plunging them back into combat using a virtual reality game that simulates scenes from Iraq and Afghanistan.

The therapeutic game, called Virtual Iraq or Virtual Afghanistan, was developed from the X-Box game Full Spectrum Warrior, a combat tactical simulation game launched with funding from the U.S. Army.