ANCHORAGE, Alaska (AP) - Genetic variation in more than 300 polar bears from Alaska was analyzed in a recent study that looked at genetic elements not used in earlier studies.
The study was conducted by University of Alaska Fairbanks Professor Matthew Cronin, who worked with colleagues at the University of California Davis and Montclair State University in New Jersey, the Anchorage Daily News (https://is.gd/ghaIv7) reported this week.
The study, published online in the Journal of Heredity in January, concludes that polar bears diverged as a separate species from brown bears 1.2 million years ago. Other studies have marked the separation at 600,000 to 4.5 million years ago.
The oldest known polar bear fossil dates back only 120,000 years.
Scientists today can look at full genomes and billions of nucleotides that lead to estimates far beyond information reflected in the fossil record. Researchers can use a “molecular clock” technique to determine when species diverged based on the number of mutations in DNA sequences. That technique places polar bears as an independent species far longer ago than previously believed.
Cronin said the “molecular clock” measures do not offer absolute certainty.
If the DNA measures are correct, however, it means bears have survived past warming cycles, he said. That should have implications for policy decisions surrounding the listing of polar bears as an endangered species, said Cronin, who has been a vocal critic of the Endangered Species Act.
“It seems logical that if polar bears survived previous warm, ice-free periods, they could survive another,” he said in a University of Alaska Fairbanks news release. “This is of course speculation, but so is predicting they will not survive, as the proponents of the Endangered Species Act listing of polar bears have done.”
Cronin said he doesn’t believe endangered species should be based on predictions and models. They should be focused on “real-world problems,” he said.
Other scientists agree polar bears have survived past warming and glaciation periods. But they diverge on whether past warming trends can be compared to the current one.
Cronin’s arguments are misleading and “incautious,” said Steven Amstrup, a U.S. Geological Survey scientist emeritus who wrote a report recommending polar bears be federally listed as threatened.
The current warming period is occurring much faster than past cycles of glacial and interglacial periods and it includes human effects, said Amstrup, now a senior scientist at Polar Bears International.
Information from: Anchorage (Alaska) Daily News, https://www.adn.com
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