A rapid shift in climate that brought wetter and warmer conditions in southern Africa during the Middle Stone Age helped propel innovation and cultural advances in early man, a study has found.

Paleontologists have long known that anatomically modern man’s technological progress moved in fits and starts in various regions of the planet.

A European team suggests that one period of abrupt change, about 40,000-80,000 years ago in what now is South Africa, matches with a climate shift brought about by cyclical changes in the currents of the Atlantic Ocean. Their findings were published...

By the end of high school, 12% of teens say they have taken a stimulant medication for reasons other than to treat attention-deficit hyperactivity disorder (ADHD). But parents, including many of those whose kids are taking ADHD drugs in a bid to boost their academic performance, appear to be clueless.

Among parents whose kids have not been prescribed ADHD medication, a University of Michigan study found, only 1% said they believed their child had used prescription stimulant medication -- including Ritalin, Adderall and Vyvanse -- as a study drug.

University of Michigan pediatrician Dr. Matthew...

More physical education in kindergarten through fifth grade means less chance of obesity, especially for boys, researchers say.

The study provides some of the first evidence of a causal effect between gym and childhood obesity. It is to be published in the Journal of Health Economics.

A number of health organizations, including the Centers for Disease Control and Prevention, have advocated for increased gym class time as one response to the dramatic rise in childhood overweight and obesity. But there has not been much known about the effect of such classes, the researchers said.

They took...

"One thing that really surprised me was how quickly it developed," said Robin Tanamachi, a postdoctoral researcher at the National Severe Storms Laboratory in Norman, Okla. "It went from being a benign-looking blip to a supercell in 10 to 15 minutes.  All the ingredients were there at the right time."

On Monday, Tanamachi, who specializes in using radar to build computer simulations of severe storms and blogs at Tornatrix.net, was...

Images showing the massive tornadoes spawned by "super cell" thunderstorms over Oklahoma, and the scars they left behind, have been released by NASA and the National Oceanic and Atmospheric Administration.

The images show the sudden outbreak of super-cell thunderstorms with strong, tight rotation.

The storms form where air masses with different temperatures and water content collide -- a common occurrence during the spring in the lower Midwest, where warm, moist air currents originating in the Gulf of Mexico meet drier, colder air masses from the upper Plains and Canada.

Warm air expands,...

For years, physicians have been inching their way to a better understanding of how -- and how well -- the drug ketamine, a "twilight drug" used to sedate some patients before a painful procedure, can lift someone with severe depression almost immediately from the abyss.

A new study, presented in San Francisco this week at the American Psychiatric Association's yearly meeting, shows that ketamine's rapid antidepressant effect is no incidental effect of sedation: it's real, and it lasts -- albeit with diminishing effects -- for at least a week.

Ketamine, which is also a drug used recreationally...

NASA’s Mars rover Curiosity has already met its mission goals, discovering that parts of the Red Planet could have been friendly to microbial life. But not one to rest on its scientific laurels, the robot has drilled a second sample of rock to back up the rover’s ground-breaking findings.

The Mars Science Laboratory rover drilled a 0.6-inch-wide and 2.6-inch-deep hole into a rock named Cumberland, which sits about nine feet west of John Klein, the first rock sampled back in March. Ground into a powder, sieved, portioned and delivered to the lab instruments in the rover’s...

A tornado researcher at the University of Alabama at Huntsville couldn't believe it when he heard Monday that a devastating twister was headed toward Moore, Okla.

"One of my graduate students came in my office yesterday and said, 'Moore is about to be hit again,' " Kevin Knupp said. "I said, what?"

Monday's devastating storm was the third major tornado to strike the town since 1999. But Knupp, whose work focuses on how external influences like features on the ground systems contribute to tornado formation, said that scientists don't know yet whether the Oklahoma City suburb's string of storm...

A record-setting Burmese python nearly 19 feet in length was captured and killed in a rural part of Miami-Dade County, officials announced this week.

Measuring 18 feet 8 inches, it is the longest Burmese python that has ever been found in the area.

The snake was discovered by Jason Leon, 23, a marine biology student at Florida International University. Leon was riding all terrain vehicles with friends in Florida City, about 35 miles south of Miami, when he spotted 3 feet of the python poking out of the brush, the Sun Sentinel reports.

Having kept Burmese pythons as pets, Leon knew to grab it...

The march of the penguins seems to mock evolution. If Emperor penguins just got up and flew 40 miles, they could get to their mates in no time flat. Why would evolution abide a tedious waddle across the ice?

It turns out there’s method in the seeming madness of these blubbery short-winged pedestrian birds. Penguins long ago faced a steep trade-off between the high calorie costs of flight and low energy expenditure of using their wings to swim. They dived into an "adaptive fitness valley" of evolution that fly-and-dive ocean birds such as murres and cormorants still straddle, according to...

A crew of Mongolian gerbils may have gone where no Mongolian gerbil has gone before, but they did not come back alive. A Russian spacecraft filled with mice, lizards and other animals has returned to Earth -- but with the majority of its furred passengers apparently dead.

The Bion-M experiment, launched from Baikonur, Kazakhstan, on April 19, carried 45 mice, 15 geckos, 18 Mongolian gerbils, 20 snails and a number of different plants, seeds and microorganisms, according to a Russian state news site. 

About half of the mice died, but the lizards reportedly survived. The Mongolian gerbils all...