A team of talented scientists has made an amazing discovery about the tiny molecules of giant creatures: they’ve found a perfectly preserved genome structure in a 52,000-year-old woolly mammoth fossil. The dried skin was so well preserved that it contained the mammoth’s chromosomes intact, giving researchers unprecedented insight into the biology of the ancient animal.
The last mammoth Mammoths went extinct 4,000 years ago, so recent that Egypt was already building some pyramids on them, but in this study, the team looked at mammoth specimens that were 52,000 and 39,000 years old, when anatomically modern humans were still around. We shared the earth with the Neanderthals.
Mammoth remains have been found throughout the grasslands where they once roamed. The hairy proboscideans’ remains are often preserved in permafrost (permanently frozen topsoil), but the thawing and refreezing process can damage the microstructure of the animals’ soft tissues. In some cases, the preservation is surprisingly good. For example, in 2022, Perfectly preserved mammoth calf The team discovered the fossils in a gold mine in the Yukon Territory. But their latest discovery reveals preservation on an entirely different scale: at the molecular level. Published Today is cell.
“We looked around, we dug down, and finally we zoomed in and saw that there was a new kind of fossil,” study co-author Erez Lieberman Aiden, a computer scientist and geneticist at Rice University, Baylor College of Medicine and the Broad Institute of MIT and Harvard, said at a press conference last Tuesday.
How did chromosomes survive for so long?
The 52,000-year-old remains examined by the team contained millimeter-sized hairs, suggesting that the mammoth had been flash-frozen. The team says that this preservation indicates that the mammoth was frozen about 10,000 years before the Neanderthals went extinct. The fact that the hair was still intact means that the skin sample had not thawed since then. This means that the animal retained its hair, hair follicles, intact cells, and of course, chromosomes folded up within the cell regions. The team could actually see the genetic loops that control whether certain genes are expressed or not.
“The samples were freeze-dried to form a kind of beef jerky,” Lieberman-Aden said. Meat that has undergone glass transitionThis made the mammoth’s skin more durable. Freeze-drying created a microscopic molecular jam that prevented the chromosomes from spreading. The skin samples served as a time capsule of ancient molecules, and the team named the flash-frozen genetic material “chromoglass.”
GIF: Vinicius Contessotto, Antonio Oliveira Jr. and Jose Onucic
The high quality of the remains allowed them to perform the first genome assembly of an extinct species, the researchers say. Mammoths had 28 chromosomes, like elephants (unlike humans, who have 23). The team reconstructed the mammoth’s chromosomes in 3D, which to humans resembles a Gordian knot, but offers researchers a remarkably accurate glimpse into the microscopic structures that helped blueprint the Ice Age steppe behemoths.
“The variation we’re capturing in this mammoth genome opens new doors for comparisons between species,” Cynthia Pérez Estrada, a researcher at Baylor College of Medicine and co-author of the paper, said at a press conference. “Just being able to see the footprint of chromatin organization in three-dimensional space is incredible.”
Mammoth “beef jerky” preserves the molecular structure of chromosomes
The team tried everything they could to erase the molecular structure of Chromograss. Instead of dried mammoth hide, they used dried Boar’s Head Beef Bologna sausage, which has virtually the same structure at the molecular level. They soaked the Chromograss beef in water, acid, and liquid nitrogen, heated it in a microwave, hit it with baseballs and mallets, ran it over with a car, verbally abused it (he joked at the press conference that he was “emotionally damaging”), and blew it up with shotgun shells (see photo below). Despite the fragmentation of the material, the chromosomal structure remained intact at the microscopic level.
“They were the first [preserved chromosomes]”We expect many more genes to be discovered in the coming years,” Olga Dudchenko, a genomics researcher at Rice University and Baylor College of Medicine and a co-author of the study, said at a press conference.
The new findings reveal the preservation of molecules never before seen in ancient remains. Old DNA has been found, and indeed several of the authors of the new paper say The oldest DNA preserved at the timeThe new fossils, discovered in the tusk of a mammoth one million years ago, make it possible to study how the mammoth’s genes were expressed and how its genome was assembled. Current record holder for oldest DNA sequence The fossil is part of a series of environmental DNA recovered from northern Greenland that allowed the team to reconstruct ancient environments from the early Pleistocene epoch.
What can scientists do with flash-frozen chromosomes?
The perfect preservation of such delicate molecular material is Extinction recoverysome scientific teams and companies Trying to create a surrogate species In fact, they represent a recently extinct animal. In particular, tracking the genes that control cold tolerance and promote hair growth could be useful to companies trying to create a 21st century mammoth. Earlier this year, one such company, Colossal Biosciences, announcedSuccessfully created stem cells from elephantsIt is the first species to have been genetically altered down to the embryonic stage, but the team stressed that bringing back extinct species is a difficult process and is not their goal.
“We are a very powerful species living on a very small planet, making important decisions about the future of humanity and the future of life on this planet in the context of climate change and so on,” Lieberman Aiden says. “This is about our ability to learn from the past.”“
AI helps decipher the tree of life
The closest living relative to the woolly mammoth is the Asian elephant. Scientists can use mammoth chromosomes to better understand elephant genetics. But elephant genetics can also help scientists understand mammoths. Scientists can feed an AI model a strand of genetic code and ask the AI where a protein might be bound in a mammoth, or how the genome might be folded.
“If you take just a little bit of data about mammoths and put it into these AIs, you get a wealth of information,” Lieberman Aiden told Gizmodo. Beyond the Asian elephant, the AI tools can contextualize the mammoth genome on the tree of life. “The incredible power of AI is that it can take insights from all these species and synthesize them to make some pretty accurate inferences,” Lieberman Aiden added.
A combination of new technology, ingenious methods, and luck is revealing the ancient world on a scale never before heard of. Understanding the giant mammoths at a molecular level not only helps us understand our ancient past, but also informs conversations about the future of extant animals.
