The finding that Lokis have actin tentacles adds plausibility to a eukaryogenesis scenario called the model upside down, Spang and Schleper said. In 2014, the cell biologist Buzz Baum at University College London and his cousin, the evolutionary biologist David Baum from the University of Wisconsin, Madison, proposed an idea they floated at family events: that the first eukaryotes were born after a single ancestral cell extended protrusions beyond its cell walls. These arms first reached out to a symbiotic bacterium. Eventually, they closed around this partner, turning it into a proto-mitochondrion. Both the original archaeal cell and the captured symbiote were enveloped in a skeleton provided by the arms.
Back when the archaea of Asgard were still known only from fragments of environmental DNA, Baum asked attendees at a conference to draw what they thought the organisms would look like. His own drawing based on the Upside-Down Ideas, which predicted that they would sport protruding arms, surprised the other scientists gathered. At the time, Schleper said, it seemed “so strange that he would make this funny suggestion.”
A competitive atmosphere
The events of eukaryogenesis have been so obscured by time and gene exchange that we may never know them for certain.
The two species of Loki currently in culture, for example, are modern organisms that differ from ancient archaea in the same way that a living, singing cardinal differs from the ancestral dinosaur from which it evolved. The Loki group isn’t even the subset of Asgard’s archaea that genetic analyzes show are most closely related to eukaryotes. (Based on known genomes of Asgard, a preprint posted by Ettema and colleagues in March argued that the ancestor of eukaryotes was an archaeon Heimdall.)
Yet labs around the world are betting that culturing more diverse representatives of the Asgard group will yield a wealth of new clues about their and our common ancestor. Schleper tries. So is Ettema. The same goes for Baum, who said his lab will soon welcome a new colleague who will bring vials of archaea from groups like Heimdall and Odin. Just like Imachi, who refused to speak to Quantum for this story.
“If I were to be interviewed by you now, I would most likely be talking about new data that has not yet been released,” he explained in an email, adding that his group applauded the team’s efforts. Schleper. “It’s very competitive now (although I don’t like that kind of competition),” he added.
Other sources also lamented the overly pressurized atmosphere. “It would be nice if the land was more open to sharing,” Spang said. The pressure is heaviest on young scientists who tend to take on high-risk, high-reward cultivation projects. Success can add shine Nature paper to their resume. But wasting years on a failed effort can reduce their chances of ever getting a job in science. “It really is an unfair situation,” Schleper said.
But for now, the race continues. When the Baum cousins published their ideas on eukaryogenesis in 2014, Buzz Baum said, they assumed we would probably never know the truth. Then, suddenly, the Asgard appeared, offering new insights into the liminal and transitional stages that propelled life from single-celled simplicity to overdrive.
“Before we destroy this beautiful planet, we should do a little research, because there are cool things on planet Earth that we know nothing about. Maybe there are things that are kind of living fossils – intermediate states,” he said. “Maybe it’s on my shower curtain.
Original story reproduced with permission from Quanta Magazine, an editorially independent publication Simons Foundation whose mission is to enhance the public understanding of science by covering developments and trends in research in mathematics and the physical and life sciences.