WASHINGTON DC: Scientists have taken “a blood sample from a real mammoth” – by using ancient DNA, they reconstructed the blood protein haemoglobin and found special adaptations to the harsh, arctic weather.
The scientists took ancient, fragmented DNA from bones 25,000 to 43,000 years old. The results showed that mammoths evolved to withstand the Arctic cold, in part, by cooling down their extremities.
“We found that, unlike living elephants, mammoth haemoglobin is able to offload oxygen to cold tissues, saving energy and hence reducing their food requirements,” said Kevin Campbell, team leader and a biologist at the University of Manitoba, Canada, who published the sudy in Nature Genetics.
“No easy feat” to get sequence of haemoglobin
“This helped to minimise heat loss,” he said. For mammoths, food was likely harder to come by and of lower quality due to harsh arctic winters. So mammoths that were able to conserve energy by trapping heat in their core were more likely to survive this inhospitable environment.
The researchers discovered the adaptations by first comparing the DNA sequences of living elephant haemoglobin genes with ancient DNA sequences obtained from the mammoths.
This was no easy feat as ancient DNA is often seriously degraded, Campbell explained. “Imagine meat sitting at the bottom of your freezer for 40,000 years – ice crystals, contaminants and time cut up and damage the DNA.”
Bacteria made the protein
Mammoth haemoglobin sequences in hand, the scientists then had to go about bringing the protein back to life.
They did this by first changing the RNA sequences that make elephant haemoglobin into mammoth RNA via a technique called site-directed mutagenesis – which allowed specific nucleotide sequences in the elephant RNA to be converted into the mammoth sequences.
After inserting the RNA into E. coli bacteria, which synthesised the mammoth protein, the researchers had what they’d worked years to recreate: Real-life mammoth blood.
“In the past, people have inferred things from DNA sequences – hair colour for example – but our paper takes things one step further by bringing the protein back to life and then studying it in great detail,” said Jeremy Austin, a team member at the Australian Centre for Ancient DNA, Adelaide.
Like taking a blood sample
“We ‘brought back’ living, breathing mammoth haemoglobin molecules,” Campbell said “which is no different than going back in time and taking a blood sample from a real mammoth.”
Roy Weber, a biology Professor at the University of Aarhus, Denmark, performed physiological testing on the mammoth and elephant haemoglobins, and discovered that three amino acid differences in the mammoth protein radically alter its oxygen-binding properties.
These differences translated to low-temperature adaptations unique to mammoths. “It’s remarkable that we found important functional changes that are not known to exist in any living animal,” Campbell said.
Fossils, DNA only tell so much
Scientists agree that this exciting new approach allows them to look at the inner workings of creatures that haven’t walked the Earth for thousands of years.
Fossils only tell part of the story of how an animal lived, said Campbell.
“Physiological processes leave no trace in the fossil record. They are like a baseball flying through the air. It used to be we only saw where the baseball landed; now we can see where it was thrown from and how it got there.”
May help with conservation
Austin also explained that by showing this type of research is possible, it opens new doors into understanding the physiological attributes of other extinct species.
“By looking at key changes in these proteins it might tell us how extinct species adapted to their environment, or maybe even why they couldn’t adapt to climate change after the Last Glacial Maximum.”
Uwe Bergmann, a Stanford physicist who has studied fossils using synchrotron X-rays, agrees: “The work sounds absolutely fascinating.”
Australian Centre for Ancient DNA at the University of Adelaide
The paper abstract in Nature Genetics