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Monday, October 16, 2006

Climate Change Is Nothing New

Global climate change isn't just a problem of the industrial age. Dinosaurs had to cope with it, too, geologists have found.

The carbon and nitrogen content of ancient rocks retrieved from the bottom of the Pacific Ocean 1,000 miles east of Japan indicate that ocean surface temperatures fluctuated by as much as 11 degrees Fahrenheit during the Cretaceous period 120 million years ago.

Scientists from Indiana University at Bloomington and the Royal Netherlands Institute for Sea Research detailed their findings in this month's issue of Geology.

Previous research had found evidence of a changeable climate in the Atlantic Ocean around the same period, but not much was known about what was going on in the Pacific, said Indiana geologist Simon Brassell, who led the new study.

Brassell said the evidence of climate change so long ago during a period without humans could influence the modern-day understanding of global warming.

"If there are big, inherent fluctuations in the system, as paleoclimate studies are showing, it could make determining the Earth's climatic future even harder than it is," he said. "We're learning our climate, throughout time, has been a wild beast."

-- Christopher Lee

Sartorial Benefits Found in Fertility

Women dress better when they are most fertile, according to a study published online last week in the journal Hormones and Behavior.

Using 30 college-age women as subjects, five researchers had a panel of 42 men and women compare photos of the women taken both when they were ovulating and when they were not, asking in which photo each woman looked more attractive. Sixty percent of the time, the panel chose the photos of the women taken when they were most fertile.

In an interview, the study's lead author, Martie G. Haselton, called the findings "highly statistically significant" and said, "We know the effects have something to do with ovulation." She added that the judges thought the women dressed increasingly attractively the closer they were to their most fertile day.

While other species emit scents or display other physical changes when they are ready to mate, researchers have traditionally assumed humans conceal their fertility, the paper's authors wrote. They added that their work suggests that ovulating women engage in "self-ornamentation through attentive personal grooming and attractive choice of dress."

"It's just showing us our evolution, our biology, is showing up in even the most modern of behaviors," said Haselton, a scientist at the Center for Behavior, Evolution and Culture at the University of California at Los Angeles.

The researchers were uncertain what was motivating these women, however: whether ovulating women may be trying to attract mates beyond their primary partners or simply reflecting a mood change, they wrote.

-- Juliet Eilperin

When Earth Tilts, Animals Fall Off

Paleontologists have long wondered why the fossil records they study often point to mass extinction of certain mammal species every 2 1/2 million years. Dutch climate experts and biologists think they have found the answer: Periodic fluctuations in the way Earth orbits, tilts and wobbles on its axis have led to climate changes that wiped the animals out.

The researchers, at the University of Utrecht in the Netherlands, looked at 80,000 fossilized rodent teeth from central Spain that had been collected over the past four decades, which came from animals that lived between 24.5 million and 2.5 million years ago.

The researchers determined which animals lived in specific time periods, and with that information they found evidence for two different cycles of die-offs that eliminated up to 30 percent of the species alive at that time. Those die-offs occurred most prominently every 2.5 million years, but also at million-year intervals.

With that information in hand, the team matched it to changes in the orbit, the tilt and the wobble of Earth. Those changes, together called the Milankovitch cycles, can greatly influence the amount of heat and light reaching Earth from the sun and cause significant global cooling when two or all three of the cycles peak together. In last week's issue of the journal Nature, the team reported that the rodent die-offs matched up to recently discovered variations in the Milankovitch cycles.

The phenomenon was not, however, quick and dramatic like the mass dinosaur extinction of 65 million years ago. It was rather a slow process by which certain species could no longer live in the increasingly cold climates of their area. Other species would then move in and take over their environmental niche.

-- Marc Kaufman

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