An international team of scientists has published the results of their research into the 23 woolly mammoth genomes of V Current Biology. As of today, we have more exciting insights into its evolution, including indications that while the woolly mammoth was indeed adapted for life in a cold environment, it continued to make more adaptations throughout its existence.
Years of research, as well as numerous woolly mammoth specimens, have enabled the team to build a better picture of how this species has adapted to the cold tundra it calls home. Perhaps most importantly, they included a genome they had previously sequenced from a woolly mammoth that lived 700,000 years ago, around the time its species first branched off from other mammoth species. Ultimately, the team compared that to an impressive 51 genomes — 16 of which are new woolly mammoth genomes: the previously mentioned genome from Chuchochia, 22 genomes of woolly mammoths from the late Quaternary period, 1 genome of an American mastodon (a relative of the mammoth), and 28 genomes from elephants. Existing Asian and African.
From this data set, they were able to find more than 3,000 genes specific to the woolly mammoth. From there, they focused on genes in which all woolly mammoths carry sequences that altered the protein compared to the copy found in their relatives. In other words, genes whose changes appear to be naturally selected.
What’s new (genetic)?
David Díez-del-Molino is an evolutionary biologist and lead author of this paper. “What we call ‘highly evolved genes’ are genes that have a lot of these non-synonymous mutations,” he explained in a video interview with Ars. “The more there are, the more highly evolved that we consider them.” The fact is (and by the way, we mention this in the limitations of the study) all mutations are related. So genes that contain only one of these mutations, can be very important to the phenotype of the woolly mammoth. So we use the number of mutations as an indicator of how much a gene has changed in the woolly mammoth.”
Some of those highly evolved genes provide insight into the woolly mammoth’s ecology. The team found evidence of genes involved in the immune system, specifically those that may be beneficial against parasitic worms or pathogens. Other genes may have helped repair DNA. Two of the genes they identified in this regard (BRCA1 And BRCA2) It is involved in the development of breast cancer in humans, and acts to suppress tumors. Could woolly mammoths, like their extant relatives, be resistant to cancer?
Some modifier genes are involved in fat storage, heat production, and metabolism, all of which can be very useful against the Arctic cold. Other changes indicate that the woolly mammoth may have altered its sense of cold, such as the ability to feel pain in response to cold temperatures.
The genes associated with hair are perhaps the most interesting. The team found changes in several genes responsible for genetic disorders in humans. With names such as non-collectible hair syndrome and the aptly named “woolly hair syndrome” (Carvajal syndrome), these disorders collectively produce hair that is thick, unkempt, wiry, and curly. However, these qualities are consistent with what we imagine woolly mammoth fur to be: a large, dense, wiry, and untearable undercoat of hair. These genes indicate that mammoth fur was not the same for all types of wool; It may have evolved over the course of its existence so that later species may have different coats than their predecessors.
It’s very funny, said Díez-del-Molino, because all the names were everything we thought mammoth hair was! But it’s important to note that we don’t know the exact function in the woolly mammoth because it’s not exactly the same mutation. [seen in humans]. “
Genes and relatives
But why are comparisons made to genetic disorders in humans? The answer lies in why we know nothing about these genes at all. In the case of the aforementioned genetic disorders, the search for the underlying causes of these diseases is why we know which genes are associated with them. For other genes, our knowledge comes from studies of other species.
“We only know the function of some genes because they are studied in some other species,” explained Diez-del-Molineux. Since we can’t study what these genes do in mammoths, the best information we get comes from studying the related genes. “We have to use agents—usually humans and mice—because they’re model species, and they’re well-studied. In the paper, we try to be a little careful when phrasing these things. We say, ‘Oh, okay.’ This gene could be associated with ear size, but we don’t really know. “
The size of the ear was another cool revelation. The gene that has undergone the most mutations over the past 700,000 years was the one that, in mice, is associated with small ears. They therefore suggest that older mammoths may have had larger ears than their later counterparts.
Today’s paper is a big jump from an equally exciting 2015 paper that unveiled the genomes of the woolly mammoth and their potential functions.
Díez-del-Molino and his team discovered that some of the genetic variants that the previous team had reported “fixed in woolly mammoths,” were not, in fact, so. This means that rather than all mammoths having the same copy of a gene, the later populations kept some variation there. Díez-del-Molino explained that he and his team enjoy more samples. While the previous team was able to sequence two woolly mammoths, today’s team was able to sample more fossils and mummies. Diez del Molino offered: “We have a lot of genomes.” Which means we have the potential to look at a lot more differently. And some woolly mammoths didn’t [the] mutations that were recorded back then.” More importantly, today’s team can compare the genome of the 700,000-year-old woolly mammoth with that of its descendants, providing crucial information about the evolutionary adaptations found in later genomes.
Ancient DNA Challenges
Rebecca Rogers is an evolutionary geneticist at the University of North Carolina at Charlotte who was not involved in the research. I found it “interesting that they were able to get quite this massive data set. They have this global view of what’s going on with mammoths.”
“I would be really interested to see what else they do with this data set and what the genetic community comes up with when they look at the same kind of data,” she said.
“One thing I would like to stress is that getting DNA from 700,000-year-old mammoths is a big sham. It’s not something I’d try myself,” she said. “And it’s the kind of test that fails most of the time. But here they have one that worked. I am sure that must have been an enormous amount of work.” She described the time it would take to discover suitable specimens and fossils in the field, and then the likely number of attempts it would take for scientists to successfully obtain ancient DNA from those specimens. Quick or easy.” So it’s kind of a high-risk, high-reward venture. And it’s nice to see people who love love [and the team] push it forward.”
She points to senior author Love Dalen, professor of evolutionary genomics at the Center for Paleogenetics in Stockholm. He and a number of co-scientists published this paper last Hereditary research inside Mammothincluding older The mammoth genome has been successfully sequenced to date. In a press release, he points out some of the unique challenges in their work.
“Apart from field work, where we have to fight both polar bears and mosquitoes, another aspect that makes it more challenging is that you have to work in an old DNA lab, and that means you have to wear your full-body suit with a hood and a mask. For the face, mask and double gloves, so doing lab work is a little uncomfortable, to put it mildly,” Dalen says. male. “I would like to highlight Marianne DeHasque, second author of this paper, who has put in the tremendous effort of performing the lab work on most of these samples.”
Arguably, there is something powerfully compelling about woolly mammoths. They are extinct, but only—in geological terms—some survived on the islands 4,000 years ago or so. It’s recent enough that amazing mummies sometimes emerge from the permafrost of Siberia and the Yukon, leaving us uniquely positioned to gather extraordinary information from the creatures that no longer walk this earth. The technology needed to conduct genetic research on extinct species has improved by leaps and bounds over the past few decades.
Rogers noted, “When I started graduate school, the animals that you could do genetics on were things like fruit flies or worms or mice. And now you can sequence any genome you choose of any species. And so we can get these reference genomes — the blueprint of the DNA of different kinds of animals.” – And then we can look at population-wide variation in anything we want now! Sequencing keeps getting cheaper and better, so it’s only opened the doors to studying different kinds of evolutionary questions in my field in the past 10 years. In the future, genome sequencing will only get better.”
“Our goal is to discover how evolution works,” said Diez del Molino. Their “typical species” is the woolly mammoth for a number of reasons. In addition to them being “wonderful animals,” he also explained that they are “extinct – which is more interesting – but more importantly, there have been many woolly mammoths for a long period of time. We have a lot of remains, and they come from Siberia where there is already permafrost So we can actually arrange it.” He describes this data set as “amazing”. And his enthusiasm is justified. “We have a genome that is very close to the origin of the species 700,000 years ago,” he said. “It was a very early version of it, and then we have many animals throughout the last 100,000 years of this species’ existence, for example. So I think from that perspective, that’s what I find interesting personally.”
Ultimately, Diez del Molino “would like to know what all these genes actually do in the woolly mammoth. That would be great.”
Cell Reports, 2023. DOI: 10.1016/j.celrep.2015.06.027
Gene Timmons (@employee) is a freelance writer with a strong passion for paleontology. Based in New Hampshire, she writes about paleontology (and some archaeology) on her blog mostmammoths.wordpress.com.
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