Focus
on Research
Penn State Intercom......September
27, 2001
Study supports out-of-Africa
origin for East Asians
By A'ndrea Messer
Public
Information
An
international study of Y chromosomal DNA shows that East Asian populations
migrated out of Africa and suggests that little or no interbreeding of
Homo erectus and Homo sapiens occurred after the migration. 
"Our goal was to test the hypothesis that the common origin of human populations is in Africa," said co-author Mark D. Shriver, assistant professor of anthropology. "We also wanted to see if there was evidence of archaic admixture of Homo erectus and Homo sapiens."
The researchers tested 12,127 male individuals from 163 East Asian populations. The Y chromosome was used because it remains the same when passed from father to son.
"The Y chromosome is nice because it does not recombine," Shriver said. "A lot more evolutionary information is available than is found in mitochondrial DNA."
Mitochondrial DNA is non-nuclear genetic material passed from mothers to their children and has been used for some previous African origin research. Researchers from China, Indonesia, England and the United States collected samples, genotyped the Y chromosomes and analyzed the results. They looked for specific mutations at three locations on the Y chromosome and found that every one of the 12,127 samples typed carried one of these three polymorphisms.
"These three markers can be used to test the completeness of the replacement of modern humans of African origin in East Asia," the researchers said. "An observation of a male individual not carrying one of the three polymorphisms would be indicative of a potential ancient origin and possibly leading to the rejection of such completeness."
This result indicates that modern humans of African origin completely replaced earlier populations in East Asia, researchers said.
Shriver warned, however, that there are some ways in which this result could be accurate, even though interbreeding took place. If all of the Y chromosomes inherited from Homo erectus were eliminated from the population because those with Homo erectus ancestors were swept from the population due to a disease to which they were especially susceptible, they would not appear in the sample. Also, if only Homo erectus women mated with Homo sapiens men, but no Homo sapiens women mated with Homo erectus men, then there would be no Y chromosomal evidence of the admixture. While these possibilities must be considered, one of the strongest components of this study is its size. The 163 population samples came from populations in Central Asia, Central Siberia, Okhotsk/Amur, Kamchatka/Chukotka, Northern East Asia, Northern Han Chinese, Southern Han Chinese, Taiwanese Aborigines, Southeast Asia, Indonesia/Malaysia, Poly/Micronesia and Northeast India, covering a broad geographic area.
The large number of populations also eliminates the possibility that genetic drift is the cause of the researcher's results. Genetic drift is a tendency for small populations to gradually alter their genetic makeup over time. The researchers find it hard to imagine that all the 163 populations should drift in the same direction.
The size of the sample, 12,000 individuals, also provides strong statistical evidence that the researcher's findings are correct. The possibility of the study missing one case of admixture in one thousand subjects is so small the number is truly minute. Even if one investigated the likelihood of one Homo erectus admixture in a million individuals, the number remains far below that which validates the result.
A'ndrea Messer can be reached at aem1@psu.edu.
Foliage could be
brilliant if the
weather
is right
Hot autumn days and mild nights -- many wish for Indian summer this time of year. But if you want a bright, colorful foliage display in October, you shouldn't, according to an expert in the College of Agricultural Sciences.
"Weather in the next month or so is very important," said Marc Abrams, professor of forest ecology and physiology. "We need to have cool temperatures falling into the high 30s or 40s at night, as well as bright sunny days with little rain."
If temperatures cool over the next four weeks with little rain falling, fall foliage watchers in Pennsylvania should be treated to a superior display of color this year, Abrams predicted.
"If we cross our fingers and Mother Nature cooperates, we should have good color by the middle of October," he said.
For 15 years, Abrams has studied how seasonal precipitation and temperature influence timing and intensity of fall colors in central Pennsylvania. "We believe that clear, bright days, low -- but not freezing -- temperatures and dry conditions promote the best fall colors," he said.
Cooler temperatures signal deciduous trees to stop producing chlorophyll, the green pigment responsible for photosynthesis, he explained. The chlorophyll breaks down and disappears, unmasking other leaf pigments. It's these other pigments -- called xanthophylls and carotenes -- that create the yellows and oranges seen in the leaves of yellow poplar, hickory, sycamore, honey locust, birch, beech and certain maples.
After chlorophyll production stops, trees also produce another pigment in their leaves called anthocyanin, Abrams ex-plained. The anthocyanins create the brilliant reds and purples seen in maple, sassafras, sumac, black gum and purple oak.
The amount of anthocyanin produced each year is related to starch levels in the tree. Trees often produce less starch during droughts. Much of Pennsylvania experienced a significant drought this summer, but Abrams doesn't believe most trees were stressed enough to significantly impact fall colors.
This year's drought, however, may cause some highly stressed trees to change color earlier than normal or to display rather dull coloration. Overall, there is still a high potential for most trees to show their true, vibrant colors this year, Abrams predicted.
Asia's investment in research parks
could teach valuable lessons 
Telecommunications professors Robert M. Frieden and Richard D. Taylor recently traveled to Singapore, China, India and Malaysia as part of an initiative funded by the Ford Foundation to research the impact of investment in technology parks on economic development in Asia.
Under the auspices of the Institute for Information Policy, the researchers are collaborating with the East-West Center in Honolulu to conduct cross-country comparisons and summarize data they have collected to learn lessons to help reduce the global digital divide. As a result of globalization, developing nations are creating information-based "technology parks" to promote investment and development in their countries.
In addition to collecting data on India, Malaysia, Singapore, China and Taiwan, as well as Hawaii and Silicon Valley, the researchers hope to provide a collection of "best practices" from which developing nations may draw information for their own benefit.