Pleistocene Extinctions

Resurrecting a mammoth gift

PUBLISHED : Sunday, 30 October, 2011, 12:00am
UPDATED : Sunday, 30 October, 2011, 12:00am


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The woolly mammoths that lived in the cold Pleistocene era may have helped humans to survive the Ice Age, but they paid a high price for it: their own extinction.

Now, the 'unselfish' extinct mammoth may help us again.

First of all let's ask: how could these 'elephants' survive the cold?

They had a woolly coat. But this is not enough to help them survive years and years of freezing cold weather and even to breed. If humans dressed in fur coats tried to spend even a day in a freezer, the cold would kill them.

The answer? Woolly mammoths used a smart anti-freeze system in their blood.

People living in cold climates commonly add anti-freeze substances, mostly containing glycerol, to the cooling water in the radiators of their cars.

Conversely, doctors often need to induce artificial hypothermia in order to cool down a body during surgery. Heart surgeons use extreme cooling to allow them to stop patients' hearts long enough to carry out surgery and then revive them.

The body is essentially in real-life suspended animation: no pulse, no blood pressure, no signs of brain activity.

The patients' bodies are cooled to 18 degrees Celsius from a normal temperature of 37 degrees. The patients are indistinguishable from someone who is actually dead.

But crucially, the cold slows the body's processes and thereby offers a window for surgery before there is a risk of brain damage. Once surgery is complete, the patient is warmed up and their heart restarted with a defibrillator.

So, how can we use cold-tolerant blood mammoth proteins for this purpose?

The mammoths, warm-blooded mammals, obviously accumulated genetic mutations in their haemoglobin gene. Haemoglobin is the blood protein that transports oxygen from the lungs to the rest of the body. It contains iron, which gives it the red colour.

In an experiment reminiscent of the movie Jurassic Park, a team led by biologist Professor Michi Hofreiter from the University of York in Britain and scientists from Australia, Canada, Germany and the United States managed to reconstruct the haemoglobin of a woolly mammoth from the DNA found in a bone.

To compare the pre-historic haemoglobin with that of modern elephants, the scientists used fragmented DNA sequences from three different 25,000- to 43,000-year-old Siberian mammoths. Their DNA was quite well preserved as the mammoth had been frozen in Siberia's ice and snow.

By recreating the mammoth haemoglobin, the team was able to compare it with that of its closest living relatives, the African and Asian elephants. They discovered that the mammoth haemoglobin had three key amino acid differences, which allowed oxygen to be released at lower temperatures more efficiently than in the haemoglobin of modern elephants. Colder temperatures usually inhibit the release of oxygen to tissues.

The differences in the haemoglobin - similar to protein structures found in Arctic reindeer - allowed the mammoth to survive at much lower temperatures, enabling the species to move to higher latitudes and eventually to conquer the Arctic.

Hofreiter wrote in Nature Genetics: 'Our study is the first one to reconstruct an evolutionary, important, adaptive trait from an extinct species using ancient DNA.'

The resulting haemoglobin had an amazing property: a more robust temperature tolerance than either that of modern Asian or African elephants and humans. It could still provide tissues with oxygen under freezing conditions.

This means the ancient protein could serve as a model for a new line of artificial haemoglobin-based oxygen carriers for use in surgery. The mammoth protein also helps to store haemoglobin in freezers and to isolate it.

Is it a crazy science fiction idea? Could we manipulate our human DNA to become cold-resistant? If that were possible, we could go skiing in Sapporo, Japan, or the Swiss Alps in shorts or bikinis.

And what would it mean for astronauts? On Venus and earth, we face global warming, but Mars, Jupiter, Saturn, Uranus, Neptune and Pluto are supercold. No life could exist on these planets.

It seems that for the second time in history, we should be saying a big thank you to the mammoth.

Reinhard Renneberg has been professor of bioanalytical chemistry at HKUST since 1994