Evolution Before Our Eyes
I'm astounded that nearly half the population in America does not believe in evolution.
Well, remember, it's been re-cast as a religious issue.
I know - but evolution has been and is the foundation of modern biology. Without a thorough understanding of the mechanisms that drive evolution, we couldn't understand many of our basic biological processes.
One reason why some people doubt evolution is that we haven't been able to witness the process, since major change happens over millions of years.
At least that's what we thought.
Now we know there are shorter timelines. For example, we recently did an episode on the evolution of human skin color, which actually dates back just one hundred thousand years. And now we have evidence that humans can evolve in an even shorter time frame; one within written history.
A fascinating study done in Tibet may show us natural selection at work. Tibet is in a mountainous area and the Tibetans live at very high altitudes. They're descendants of the Han Chinese, who migrated to the Himalayas four thousand years ago.
The study compared Tibetan genes with the Han Chinese, who live at sea level.
By sequencing and analyzing the genomes of people from the two groups, researchers found that ninety percent of Tibetans have what's called the EPAS1 gene mutation, while just ten percent of the Hans have it. The EPAS1 gene controls oxygen sensing in human cells.
That means Tibetans may have evolved to more efficiently regulate oxygen uptake, which allowed them to thrive in the lower oxygen environments of the Himalayas. This is evolution at work!
The study was possible thanks only to whole genome sequencing, which is becoming less expensive. With effective bioinformatics tools, we can continue to compare genes, and uncover more human evolution at work.
More Information
Tracing Evolution's Recent Fingerprints
This is a informative News Focus report in a highly respected science journal on evidence of recent human evolution:
“For Rasmus Nielsen, it was a revelatory moment. He was analyzing the frequency of different mutations in the genomes of Tibetans living at high altitude, searching for adaptations that allow them to thrive in thin air. His team's analysis had generated a graph in which most of the mutations were clustered together. But two stood apart, indicating they existed in almost all Tibetan highlanders but not in their close relatives, the Han Chinese.” Science 329: 740-742; 2010.
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Sequencing of 50 Human Exomes Reveals Adaptation to High Altitude
Xin Yi*, Yu Liang, Emilia Huerta-Sanchez et al.
Original journal article about the sequencing of the genomes of Tibetans that revealed gene changes in the EPAS1 gene that have allowed adaptation to high altitude living. Science 2 July 2010: Vol. 329 no. 5987 pp. 75-78; DOI: 10.1126/science.1190371
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Human Genome Shows Proof of Recent Evolution, Survey Finds
Scott Norris, National Geographic News, March 8, 2006
This is an excellent National Geographic article presenting proof of recent evolution in the human genome:
"Signs of recent evolution by natural selection are widespread across the human genome, experts say. Genome researchers at the University of Chicago have identified more than 700 regions in human DNA where apparently strong selection has occurred, driving the spread of genes linked to a broad range of characteristics"
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