Small DNA differences in humans are ‘average’ in animal kingdom
Researchers report important new insights into evolution following a study of mitochondrial DNA from about 5 million specimens covering about 100,000 animal species.
Mining “big data” insights from the world’s fast-growing genetic databases and reviewing a large literature in evolutionary theory, researchers at The Rockefeller University in New York City and the Biozentrum at the University of Basel in Switzerland, published several conclusions today in the journal Human Evolution. Among them:
- In genetic diversity terms, Earth’s 7.6 billion humans are anything but special in the animal kingdom. The tiny average genetic difference in mitochondrial sequences between any two individual people on the planet is about the same as the average genetic difference between a pair of the world’s house sparrows, pigeons or robins. The typical difference within a species, including humans, is 0.1% or 1 in 1,000 of the “letters” that make up a DNA sequence.
- Genetic variation – the average difference in mitochondria DNA between two individuals of the same species – does not increase with population size. Because evolution is relentless, however, the lack of genetic variation offers insights into the timing of a species’ emergence and its maintenance.
- The mass of evidence supports the hypothesis that most species, be it a bird or a moth or a fish, like modern humans, arose recently and have not had time to develop a lot of genetic diversity. The 0.1% average genetic diversity within humanity today corresponds to the divergence of modern humans as a distinct species about 100,000 – 200,000 years ago – not very long in evolutionary terms. The same is likely true of over 90% of species on Earth today.
- Genetically the world “is not a blurry place.” Each species has its own specific mitochondrial sequence and other members of the same species are identical or tightly similar. The research shows that species are “islands in sequence space” with few intermediate “stepping stones” surviving the evolutionary process.
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