Feb 19, 2026 09:23 PM
(This post was last modified: Feb 19, 2026 09:23 PM by C C.)
https://www.eurekalert.org/news-releases/1116590
PRESS RELEASE: The most widely accepted scientific explanation for the arrival of all complex life on Earth has had an unsolved mystery at its heart. According to the theory, all plants, animals and fungi, known collectively as eukaryotes, are thought to have evolved after two very different types of microbes came together. The problem was in figuring out how the two were in such close proximity in the first place, given that one of the microbes requires oxygen for survival and the other was known to live in spaces without oxygen.
Now scientists from The University of Texas at Austin, publishing in the journal Nature, appear to have solved the mystery. One of our microbial ancestors was part of a group called the Asgard archaea, which today live primarily in the deep sea and other oxygen-free spaces. But according to the new study, some Asgards use, or at least tolerate oxygen. The discovery lends more credence to the idea that complex life evolved as the theory predicted—and apparently in an oxygen-rich environment.
“Most Asgards alive today have been found in environments without oxygen,” explained Brett Baker an associate professor of marine science and integrative biology at UT. “But it turns out that the ones most closely related to eukaryotes live in places with oxygen, such as shallow coastal sediments and floating in the water column, and they have a lot of metabolic pathways that use oxygen. That suggests that our eukaryotic ancestor likely had these processes, too.”
Baker and his team research Asgard archaea genomes, uncovering new lineages, expanding enzymatic diversity and exploring their metabolic pathways. The team’s latest finding agrees with the picture geologists and paleontologists have reconstructed of Earth’s history. Until about 1.7 billion years ago, Earth’s atmosphere had very little oxygen. Then, oxygen levels spiked dramatically, like levels seen today. Within a few hundred thousand years after this Great Oxidation Event, the first known microfossils of eukaryotes appeared, suggesting that the presence of oxygen might have been important for the origin of complex life.
“The fact that some of the Asgards, which are our ancestors, were able to use oxygen fits in with this very well,” Baker said. “Oxygen appeared in the environment, and Asgards adapted to that. They found an energetic advantage to using oxygen, and then they evolved into eukaryotes.”
Scientists believe eukaryotes arose when an Asgard archaeon developed a symbiotic relationship with an alphaproteobacterium. Eventually, they become one organism with the latter evolving to become an energy-producing organelle within eukaryotes called the mitochondria. In the new paper, the scientists vastly expand the number of Asgard archaea genomes and point to specific types of Asgard archaea, such as Heimdallarchaeia, which are closely related to eukaryotes but less common today.
“These Asgard archaea are often missed by low-coverage sequencing,” said co-author Kathryn Appler, a postdoctoral researcher at the Institut Pasteur in Paris, France. “The massive sequencing effort and layering of sequence and structural methods enabled us to see patterns that were not visible prior to this genomic expansion.” (MORE - details)
PRESS RELEASE: The most widely accepted scientific explanation for the arrival of all complex life on Earth has had an unsolved mystery at its heart. According to the theory, all plants, animals and fungi, known collectively as eukaryotes, are thought to have evolved after two very different types of microbes came together. The problem was in figuring out how the two were in such close proximity in the first place, given that one of the microbes requires oxygen for survival and the other was known to live in spaces without oxygen.
Now scientists from The University of Texas at Austin, publishing in the journal Nature, appear to have solved the mystery. One of our microbial ancestors was part of a group called the Asgard archaea, which today live primarily in the deep sea and other oxygen-free spaces. But according to the new study, some Asgards use, or at least tolerate oxygen. The discovery lends more credence to the idea that complex life evolved as the theory predicted—and apparently in an oxygen-rich environment.
“Most Asgards alive today have been found in environments without oxygen,” explained Brett Baker an associate professor of marine science and integrative biology at UT. “But it turns out that the ones most closely related to eukaryotes live in places with oxygen, such as shallow coastal sediments and floating in the water column, and they have a lot of metabolic pathways that use oxygen. That suggests that our eukaryotic ancestor likely had these processes, too.”
Baker and his team research Asgard archaea genomes, uncovering new lineages, expanding enzymatic diversity and exploring their metabolic pathways. The team’s latest finding agrees with the picture geologists and paleontologists have reconstructed of Earth’s history. Until about 1.7 billion years ago, Earth’s atmosphere had very little oxygen. Then, oxygen levels spiked dramatically, like levels seen today. Within a few hundred thousand years after this Great Oxidation Event, the first known microfossils of eukaryotes appeared, suggesting that the presence of oxygen might have been important for the origin of complex life.
“The fact that some of the Asgards, which are our ancestors, were able to use oxygen fits in with this very well,” Baker said. “Oxygen appeared in the environment, and Asgards adapted to that. They found an energetic advantage to using oxygen, and then they evolved into eukaryotes.”
Scientists believe eukaryotes arose when an Asgard archaeon developed a symbiotic relationship with an alphaproteobacterium. Eventually, they become one organism with the latter evolving to become an energy-producing organelle within eukaryotes called the mitochondria. In the new paper, the scientists vastly expand the number of Asgard archaea genomes and point to specific types of Asgard archaea, such as Heimdallarchaeia, which are closely related to eukaryotes but less common today.
“These Asgard archaea are often missed by low-coverage sequencing,” said co-author Kathryn Appler, a postdoctoral researcher at the Institut Pasteur in Paris, France. “The massive sequencing effort and layering of sequence and structural methods enabled us to see patterns that were not visible prior to this genomic expansion.” (MORE - details)