Tag Archives: Ice Age

Teeth from Siberian mammoths yield oldest DNA ever recovered

By Will Dunham

WASHINGTON (Reuters) – Scientists have recovered the oldest DNA on record, extracting it from the molars of mammoths that roamed northeastern Siberia up to 1.2 million years ago in research that broadens the horizons for understanding extinct species.

The researchers said on Wednesday they had recovered and sequenced DNA from the remains of three individual mammoths – elephant cousins that were among the large mammals that dominated Ice Age landscapes – entombed in permafrost conditions conducive to preservation of ancient genetic material.

While the remains were discovered starting in the 1970s, new scientific methods were needed to extract the DNA.

The oldest of the three, discovered near the Krestovka river, was approximately 1.2 million years old. Another, from near the Adycha river, was approximately 1 to 1.2 million years old. The third, from near the Chukochya river, was roughly 700,000 years old.

“This is by a wide margin the oldest DNA ever recovered,” said evolutionary geneticist Love Dalén of the Center for Palaeogenetics in Sweden, who led the research published in the journal Nature.

Until now, the oldest DNA came from a horse that lived in Canada’s Yukon territory about 700,000 years ago. By way of comparison, our species, Homo sapiens, first appeared roughly 300,000 years ago.

DNA is the self-replicating material that carries genetic information in living organisms – sort of a blueprint of life.

“This DNA was extremely degraded into very small pieces, and so we had to sequence many billions of ultra-short DNA sequences in order to puzzle these genomes together,” Dalén said.

Most knowledge about prehistoric creatures comes from studying skeletal fossils, but there is a limit to what these can tell about an organism, particularly relating to genetic relationships and traits.

Ancient DNA can help fill in the blanks but is highly perishable. Sophisticated new research techniques are enabling scientists to recover ever-older DNA.

“It would be a wild guess, but a maximum of two to three million years should be doable,” Dalén said.

That could shed light on some bygone species but would leave many others unattainable – including the dinosaurs, who went extinct 66 million years ago.

“When we can get DNA on a million-year time scale, we can study the process of speciation (formation of new species) in a much more detailed way. Morphological analyses on bones and teeth usually only allow researchers to study a handful of characteristics in the fossils, whereas with genomics we are analyzing many tens of thousands of characteristics,” Dalén said.

The researchers gained insights into mammoth evolution and migration by comparing the DNA to that of mammoths that lived more recently. The last mammoths disappeared roughly 4,000 years ago.

The oldest of the three specimens, the Krestovka mammoth, belonged to a previously unknown genetic lineage that more than 2 million years ago diverged from the lineage that led to the well-known woolly mammoth.

Geneticist Tom van der Valk of SciLifeLab in Sweden, the study’s first author, said it appears that members of the Krestovka lineage were the first mammoths to migrate from Siberia into North America over a now-disappeared land bridge about 1.5 million years ago, with woolly mammoths later migrating about 400,000 to 500,000 years ago.

The Adycha mammoth’s lineage apparently was ancestral to the woolly mammoth, they found, and the Chukochya individual is one of the oldest-known woolly mammoth specimens.

DNA analyses showed that genetic variants associated with enduring frigid climes such as hair growth, thermoregulation, fat deposits, cold tolerance and circadian rhythms were present long before the origin of the woolly mammoth.

(Reporting by Will Dunham, Editing by Rosalba O’Brien)

Latest Study Warns “Day After Tomorrow” Ice Age Closer Than We Think

When the apocalyptic film first released, critics from both the entertainment and science communities ridiculed the movie over the possibility of climate change having such an extreme affect on the world. However, a recent study by researchers from the University of Southampton has found that we are closer to a “Day After Tomorrow” scenario than we thought.

In the film, climate warming results in the collapse of the Atlantic Meridional Overturning Circulation (AMOC) – a major current in the Atlantic Ocean that has a northward flow of warm, salty water in the upper layers of the Atlantic and a southward flow of colder water in the deep Atlantic. This leads to New York being flooded, tornadoes in Los Angeles, and finally the north hemisphere freezing and experiencing an Ice Age.

Researchers discovered that if global warming and the collapse of the AMOC occur at the same time, the Earth will cool for a period of 20 years. After the 20 years, global warming would continue as if the AMOC never collapsed and the global average temperature would offset by approximately 0.8 degrees Celsius. They used an advanced climate model at Germany’s Max-Planck Institute to simulate the conditions.

“The planet earth recovers from the AMOC collapse in about 40 years when global warming continues at present-day rates, but near the eastern boundary of the North Atlantic (including the British Isles) it takes more than a century before temperature is back to normal,” Professor Sybren Drijfhout, from Ocean and Earth Science Department at the University of Southampton, said in the release.

The AMOC depends on a connect of the warm north waters and the cool southern waters that flow deep in the North Atlantic. Due to global warming, the Greenland ice sheet has begun to melt into the AMOC, affecting the balance of the warm and cold waters. Currently, it is causing the AMOC to slow down, but it will eventually collapse.

While the climate sequence in the movie is sped up and exaggerated, the researchers still noted that the consequences from the AMOC collapse would be no less cause for worry.

The simulation showed that Western Europe would be hit the hardest by cold temperatures but America would have to contend with floods. Sea levels on the U.S. East Coast would rise more than three feet, and the UK, Denmark, and the Netherlands would see a 35-degree temperature drop.

“This would affect hundreds of millions of people,” Drijfhout said, “At least temporarily, Europe would suffer conditions that would look like the Little Ice Age of the Middle Ages.”

“When it comes to climate change, we are playing a dangerous game,” he added.