A Canadian-led team of researchers has produced a functioning blood protein using DNA recovered from preserved woolly mammoth bones.
The researchers, led by biologist Kevin Campbell of the University of Manitoba, say their work shows how the animals survived the cold of the Siberian Arctic.
Campbell calls the mammoth hemoglobin his lab manufactured "a living, breathing molecule."
"It was synthesized in our lab, but it is no different than had I gone in a time machine 43,000 years into the past and taken a blood sample from a living, breathing mammoth," said Campbell.
The scientists extracted the DNA for hemoglobin — a protein in the blood that carries oxygen — from the bones of three mammoths found frozen in the permafrost. The mammoths lived between 25,000 and 45,000 years ago.
The researchers then converted the hemoglobin DNA into the equivalent RNA, the genetic material that organisms use as a template to build proteins.
They inserted the mammoth RNA into E. coli bacteria, and the cellular machinery of bacteria created working woolly mammoth hemoglobin.
The protein itself isn't alive, but it works just as if it had been taken from a live animal.
"We've brought back an important physiological trait from an extinct species," said Campbell. "Physiological attributes simply do not fossilize, and up until this point, these have really been beyond the inquiry of science."
"It has been remarkable to bring a complex protein from an extinct species back to life and discover important changes not found in any living species," said Alan Cooper of the University of Adelaide in Australia, in a statement.
Hemoglobin is the protein in blood that carries oxygen from the lungs and brings it to the rest of the body. However, hemoglobin has trouble releasing oxygen at very low temperatures.
Delivered at low temperatures
Researcher Roy Weber at the University of Aarhus, Denmark, compared the protein to those found in modern-day elephants and found three chemical changes in the woolly mammoth hemoglobin that allowed oxygen to be delivered to cells even at low temperatures.
"This is the first study where we actually can trace the physiological processes which underlie the adaptation to cold in the elephant lineage," said Weber.
The common ancestor of mammoths and elephants initially evolved in a tropical climate in Africa. The mammoths migrated north, eventually going to the Arctic about two million years ago. The hemoglobin changes are part of the animals' natural adaptation to the colder environment, the researchers said.
"This is one piece of the puzzle as to how these animals moved into and survived the extreme conditions of the Arctic," said Campbell.
"Our approach opens the way to understand how, at the molecular level, extinct species adapted to paleoenvironments that are no longer present on Earth," he said.
The research appears this week in the journal Nature Genetics.