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1 .This is Scientific American 60-Second Science. I'm Cynthia Graber.Got a minute?
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2 .The term pygmy usually refers to a few groups of short-statured people in equatorial rain forest regions in Africa.
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3 .The existence of distinct populations of such people presented scientists with the opportunity to study the mechanisms by which typical human growth patterns have become altered there.
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4 .And they discovered that two groups became small in two different ways.
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5 .The study is in the journal Nature Communications.
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6 .The researchers collected data on some 500 members of a West African ethnic group called the Baka.
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7 .They discovered that Baka infants have a similar size range to most other infants,
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8 .but have a low growth rate during their first two years, which produces a lasting effect.
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9 .This mechanism seems to be different from that of the East African groups called the Efe and Sua.
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10 .These peoples have slow prenatal growth, so that the infants are born smaller.
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11 .The researchers say that the Baka population appears to have split from the Efe and Sua some 20,000 years ago.
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12 .The two different systems for achieving small stature,which appears to be advantageous in the equatorial rainforest environment are thus an example of convergent evolution.
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13 .The researchers believe the findings say something important about human evolution and development in general:
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14 ."Homo sapiens could therefore be characterized by its high capacity for growth plasticity during infancy.
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15 .This capacity, which may be unique to our species, may have played a fundamental role in the biological adaptation that enabled its worldwide expansion and occupation of dissimilar environments within a short period after moving out of Africa."
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16 .Thanks for the minute, for Scientific American 60-Second Science. I'm Cynthia Graber.
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