Hybrid Mammoth DNA Found

Mitochondrial DNA analysis of a Columbian mammoth (Mammuthus columbi) found in Utah suggests that its mitochondrial DNA was nearly identical to that of the woolly mammoth (Mammuthus primigenius).


[Ranges of Columbian and Wolly mammoths (Genome Biology).]

"We think this individual may have been a woolly-Columbian hybrid," said Jacob Enk of the McMaster Ancient DNA Centre, the group that led the research, which was recently published in Genome Biology.

"Living African elephant species interbreed where their ranges adjoin, with males of the bigger species out-competing the smaller for mates," he explained in a press release. The mitochondrial genomes in the smaller females then show up in populations of the larger species. "Since woolly and Columbian ranges periodically overlapped in time and space, it's likely that they engaged in similar behaviour and left a similar genetic signal," Enk said.

Modern examples of this can be seen where two varieties of elephant in Africa encounter each other. The larger savanna elephant (Loxodonta africana africana) and the smaller forest elephant (Loxodonta africana cyclotis) are capable of interbreeding. Genetic evidence has fueled a debate that these two modern elephants are indeed separate species.

The hybridization of mammoths may explain other fossils that look like intermediates between the two species. These fossils were sometimes assigned to the species Mammathus jeffersonii, but further research may show them to be hybrids of the woolly and Columbian mammoths.

The woolly mammoth was a smaller furrier beast, that lived in the north closer to the glaciers of the Ice Ages, from Alaska through Canada, and east to the Great Lakes and New England. The larger Columbian mammoth lived further south. It inhabited the western and southern portion of the U.S. as far south as Florida, and nearly to Chiapas in Mexico.

The mammoths should not be confused with the American mastodon (Mammut americanum), another ancient elephant from North and Central America.
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References:

Wall, Tim. 2011. "Hybrid Mammoth DNA Found". Discovery News. Posted: June 1, 2011. Available online: http://news.discovery.com/animals/hybrid-mammoth-mix-breeds-possible-110601.html

Mammoth resurrection on the way?

The long-extinct woolly mammoth could be resurrected within five years, thanks to recent advances in cloning technology.

Japanese researchers plan to collect mammoth tissue this summer from a carcass that was frozen in the Siberian permafrost and is now in a Russian research laboratory, according to a report in the Yomiuri Shimbun.

The hope is to recover an undamaged nucleus of a mammoth cell from this tissue and insert it into an elephant egg cell from which the nucleus has been removed. This will create an embryo with mammoth genes, according to the news report.

This embryo will be inserted to the elephant's womb in hopes that she'll give birth to a mammoth.

"Preparations to realize this goal have been made," Akira Iritani, a team leader from Kyoto University, told the Yomiuri Shimbun.

New technique

Previous attempts to recover nuclei from frozen tissue failed because the cold temperatures damaged the DNA.

The new technique is based on work by Teruhiko Wakayama of the Riken Center for Developmental Biology, who in 2008 cloned a mouse from the cells of another mouse that were frozen for 16 years.

Iritani says his team has devised a method to extract the nuclei of mammoth cells without damaging them. "Now that the technical problems have been overcome, all we need is a good sample of soft tissue from a frozen mammoth," he told London's Daily Telegraph.

Mammoth for display

If the team is successful in creating an embryo, they will discuss how to breed the mammoth — and whether or not to display it to the public — before transplanting to a surrogate elephant, Iritani told the Yomiuri Shimbun.

Even if the embryo is successfully created and implanted, the chances of bringing a cloned mammoth to term (or any cloned animal, for that matter) are slim. When South Korean researchers tried cloning dogs, for example, nearly 1,100 embryos were transplanted to surrogate dogs, but only two live births resulted, and only one of those puppies survived past the 22-day mark.

Nevertheless, Iritani was confident of success. "After the mammoth is born, we'll examine its ecology and genes to study why the species became extinct and other factors," he said.

Woolly mammoths went extinct at the end of the Ice Age, about 10,000 years ago. Scientists have long debated whether climate change or human hunters were the cause of their demise.

Last December, researchers said another factor could be the fact that the creatures delayed weaning their young due to the long dark winter north of the Arctic Circle.
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References:

Roach, John. 2011. "Mammoth resurrection on the way?". MSNBC. Posted: January 18, 2011. Available online: http://cosmiclog.msnbc.msn.com/_news/2011/01/18/5870423-mammoth-resurrection-on-the-way

Mammoths Hung on Longer? Late-Surviving Megafauna Exposed by Ancient DNA in Frozen Soil

Extinct woolly mammoths and ancient American horses may have been grazing the North American steppe for several thousand years longer than previously thought. After plucking ancient DNA from frozen soil in central Alaska, a team of researchers used cutting-edge techniques to uncover "genetic fossils" of both species locked in permafrost samples dated to between 7,600 and 10,500 calendar years.

This new evidence suggests that at least one population of these now-extinct mammals endured longer in the continental interior, challenging the conventional view that these and other large species, or megafauna, disappeared from the Americas about 12,000 years ago.

"We don't know how long it takes to pinch out a species," says Ross MacPhee, Curator of Mammalogy at the American Museum of Natural History. "Extinctions often seem dramatic and sudden in fossil records, but our study provides an idea of what an extinction event might look like in real time, with imperiled species surviving in smaller and smaller numbers until eventually disappearing completely."

At the end of the Pleistocene, the geological epoch roughly spanning 12,000 to 2.5 million years ago, many of the world's megafauna, such as giant sloths, saber-toothed cats, dire wolves, stag-moose, and mammoths, vanish from the geological record. Some large species such as Equus caballus, the species from which the domestic horse derives, became extinct in North America but persisted in small populations elsewhere. Because of the apparent sudden disappearance of many megafaunal species in North America, some scientists have proposed cataclysmic explanations like human overhunting, an extraterrestrial impact, and the introduction of novel infectious diseases. The swiftness of the extinctions, however, is not suggested directly by the fossils themselves but is inferred from radiocarbon dating of bones and teeth discovered on the surface or buried in the ground. Current "macrofossil" evidence places the last-known mammoths and wild horses between 13,000 and 15,000 years ago.

But hard remains of animals are rarely preserved, difficult to find, and laborious to accurately date because of physical degradation. Because of this, MacPhee and co-authors Eske Willerslev of the University of Copenhagen in Denmark, Richard Roberts of the University of Wollongong in Australia, and Duane Froese of the University of Alberta in Canada decided to tackle the problem by dating the "last survivors" through dirt. Frozen sediments from the far north of Siberia and Canada can preserve small fragments of animal and plant DNA exceptionally well, even in the complete absence of any visible organic remains, such as bone or wood.

"In principle, you can take a pinch of dirt collected under favorable circumstances and uncover an amazing amount of forensic evidence regarding what species were on the landscape at the time," says Willerslev, director of the Centre for GeoGenetics at the University of Copenhagen. "The use of ancient DNA offers the possibility of being able to sample previous life within the last 400,000 years, freeing us from having to rely on skeletal and other macrofossil evidence as the only way to collect information about species that are no longer with us."

In order to prospect for genetic fossils, the team collected soil cores from undisturbed Alaskan permafrost. Wind-blown Stevens Village, situated on the bank of the Yukon River, fit the bill perfectly. Here, sediments were sealed in permafrost soon after deposition. Two independent methods (radiocarbon and optically stimulated luminescence) were used to date plant remains and individual mineral grains found in the same layers as the DNA.

"With these two techniques, we can be confident that the deposits from which the DNA was recovered haven't been contaminated since these lost giants last passed this way," said Roberts, director of the Centre for Archaeological Science at the University of Wollongong. "It's a genetic graveyard, frozen in time."

Cores collected at Stevens Village offer a clear picture of the local Alaskan fauna at the end of the last ice age. The oldest sediments, dated to about 11,000 years ago, contain remnant DNA of Arctic hare, bison, and moose; all three animals were also found in higher, more recent layers, as would be expected. But one core, deposited between 7,600 and 10,500 years ago, confirmed the presence of both mammoth and horse DNA. To make certain that the integrity of this sample had not been compromised by geologic processes (for example, that ancient DNA had not blown into the surface soils), the team did extensive surface sampling in the vicinity of Stevens Village. No DNA evidence of mammoth, horse, or other extinct species was found in modern samples, a result that supports previous studies which have shown that DNA degrades rapidly when exposed to sunlight and various chemical reactions.

"The fact that we scored with only one layer is not surprising," says MacPhee. "When you start going extinct, there will be fewer and fewer feet on the ground, and thus less and less source material for ancient DNA such as feces, shed dermal tissues, and decaying bodies."

The team also developed a statistical model to show that mammoth and horse populations would have dwindled to a few hundred individuals by 8,000 years ago.

"At this point, mammoths and horses were barely holding on. We may actually be working with the DNA of some of the last members of these species in North America," says permafrost expert Froese, associate professor in the Department of Earth and Atmospheric Sciences at the University of Alberta. "The Yukon Flats includes large shifting river bars with an abundance of high quality forage where large mammals can and could make a living. There may have been a handful of similar sites in Alaska, hosting small remnant populations," says Froese.

"Dirt DNA has lots of exciting potential to contribute to extinction debates in other parts of the world too, as well as a range of archaeological questions," said Willerslev, who also points out that the approach is not restricted to looking back at the past. "We can also use it to make a list of modern species living in any particular location," he said. "This kind of information is really valuable for studies of animals that are hard to detect, and there are some neat forensic applications too."

The new paper is published in the Proceedings of the National Academy of Sciences. In addition to Willerslev, MacPhee, Froese, and Roberts, authors include James Haile, Morten Rasmussen, and Thomas Gilbert of the University of Copenhagen in Denmark; Alberto Reyes, and Simon Robinson of the University of Alberta in Canada; Lee Arnold and Martina Demuro of the University of Wollongong in Australia; Rasmus Nielsen and Kasper Munch of the University of California at Berkeley; Barry Brook, Jeremy Austin, and Alan Cooper of the University of Adelaide in Australia; Ian Barnes of the Royal Holloway University of London in the United Kingdom; and Per Moller of Lund University in Sweden. The research was funded by the Danish National Research Foundation, the Natural Science and Engineering Research Council of Canada, the Alberta Ingenuity Foundation, the Australian Research Council; Discovery Communications, Inc.; the AHRB, and the Arts and Humanities Research Council.

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References:

2009. "Mammoths Hung on Longer? Late-Surviving Megafauna Exposed by Ancient DNA in Frozen Soil. Science Daily. " Posted: December 15, 2009. Available online: http://www.sciencedaily.com/releases/2009/12/091214151946.htm