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Stories of Modern Science ... from UPI

By MICHAEL HOFFMAN, UPI Science News   |   May 29, 2003 at 9:04 AM   |   Comments

HUMAN SPECIES' AFRICAN EXIT TRACED

The first trip out of Africa by human beings occurred about 70,000 years ago, a study done by geneticists suggests. At the time of the first migration out of the continent, where scientists trace the origin of the human species, the entire human population consisted of 2,000 people. The study, by geneticists from Stanford University and the Russian Academy of Sciences, used DNA taken from 1,056 individuals from 52 geographic sites in Africa, Eurasia, East Asia, Oceania and the Americas. The new research, published in the American Journal of Human Genetics, confirmed the "out-of-Africa" theory where the human population migrated, in order, from Africa into Eurasia, Oceania, East Asia and the Americas. The scientists also estimated the human population expansion started about 25,000 years ago when technological advances increased the prehistoric species' life expectancy and birth rate.


CONCRETE CITIES CAUSES COASTAL RAIN INFLUX

The increase in coastal cities' rainfall was attributed by a new NASA study to the warming affects of urban pavement and buildings. Cities such as Houston, with high concentrations of asphalt and concrete in roads, buildings, and parking lots, retain heat and create "heat islands," which combine with sea breezes to form clouds that result in more rainfall. Similar research already had been done with inland cities such as Atlanta and St. Louis, but this is the first such confirmation of the same effect on coastal cities. The study, published in the journal Earth Interactions, also reported on the timing of rainfall in coastal cities -- rain there occurs twice as often between noon and midnight. The research applies not only to the city limits, but also to downwind regions. From 1998 to 2002, for example, the study shows warm season rainfall rates were 44 percent greater in downwind areas compared to upwind.


STRONGER THAN PEARLS?

The inside of an oyster can hold not only the riches of a pearl, but the answer to revolutionary new aircraft parts and artificial bones. Scientists have developed a nanoscale, layered material with properties resembling the nacre, the gleaming white layer inside an oyster's shell, which is extremely strong and lightweight. Natural nacre gets its strength and flexibility from the brick-like structure made up of proteins and calcium carbonate. The artificial nacre uses a similar pattern, but it uses layers of clay and a polymer called poly-electrolyte. Artificial nacre could be used to produce body armor and biocompatible substances for growing human tissues or organs, Oklahoma State University researchers said. They added because they can add new components to the material, such as ultraviolet light or corrosion-resistant chemicals, the same manufacturing process can tailor new substances to a variety of applications.


CITY SCHOOLS HEAP BENEFITS ON RICH

School districts tend to transfer millions of dollars each year from schools in poor neighborhoods to those with wealthier students and higher-paid teachers. University of Washington researchers found school districts allocate money as if all schools pay their teachers the same. Schools in wealthier communities therefore tend to receive more money to pay higher teachers' salaries while teachers in poorer neighborhoods are not compensated comparably. Also, more experienced teachers who receive the higher salaries tend to move toward wealthier neighborhoods according to union rules and longstanding practice. A system that would account for this discrepancy in teacher pay could funnel more money into the poorer schools and help stimulate improvements by shrinking classes and adding new technology. The researchers suggest taking into account not only teachers' salaries but also incentives for the higher-paid teachers to teach in the poorer schools.


(Editors: For more information on AFRICAN EXIT, contact Mark Shwartz at 650-723-9296 or mshwartz@stanford.edu. For CONCRETE CITIES, Krishna Ramanujan at 301-286-3026 or kramanuj@pop900.gsfc.nasa.gov. For PEARLS, Josh Chamot at 703-292-7730 or jchamot@nsf.gov. For SCHOOLS, Steven Goldsmith at 206-543-2580 or sgolds@u.washington.edu.)

© 2003 United Press International, Inc. All Rights Reserved. Any reproduction, republication, redistribution and/or modification of any UPI content is expressly prohibited without UPI's prior written consent.
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