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The origin of eukaryotes: how did we get from Asgard archaea to humans?
What links humans to fungi, starfish to trees, or butterflies to algae? One of the most fascinating questions in science is the origin of eukaryotes, and researchers are still searching for answers as to how the complex cells from which all animals, plants and fungi evolved first came into being – and how all of this can be traced back to a microscopic common ancestor that lived billions of years ago.
Although life on Earth is astonishingly diverse, at the cellular level it is built on surprisingly similar foundations. The origin of eukaryotes has been one of the most pressing questions in evolutionary biology for decades, and solving it plays a key role in understanding how complex life emerged on our planet.
These are organisms whose cells possess a true, membrane-bound nucleus. This group includes all animals, plants, fungi and insects – from the simplest unicellular forms all the way to humans.
As IFLScience also reports, scientists have long been trying to unravel how these cells could have evolved from simpler prokaryotes lacking a nucleus. One of the most widely accepted theories suggests that the origin of eukaryotes can be explained by an exceptionally close symbiosis: an ancient archaeal cell entered into a partnership with an oxygen-using bacterium, which later evolved into the mitochondrion.
The role of Asgard archaea in the origin of eukaryotes
The decisive breakthrough came in 2023, when researchers at the University of Texas at Austin analysed the genomes of several hundred archaeal microbes. Their results indicate that the origin of eukaryotes can be traced back to a single, well-defined archaeal lineage: the so-called Asgard archaea.
What makes these organisms special is that their genetic material contains proteins that were previously thought to occur exclusively in eukaryotic cells. This alone suggests that these ancient microorganisms already possessed the foundations of complex cellular structures long before the first true eukaryotes appeared.
During the research, a new order was also identified, the Hodarchaeales group, which inhabits marine sediments. From an evolutionary perspective, these organisms may be extremely close to the ancestral form from which all known eukaryotes originated.
Are we all Asgardians?
According to evolutionary biologist Brett Baker, one of the study’s authors, the origin of eukaryotes can now be supported not merely by abstract inferences, but by genetic data that underpin earlier hypotheses, as Asgard archaea can be regarded as our sister group within the archaeal domain.
The mythological naming is no coincidence either. In Norse mythology, Asgard is the home of the gods, while Hod (Höðr) is a son of Odin. The playful naming alludes to the idea that these organisms represent a divine turning point in the history of life: the moment when simple cells gave rise to complex organisms.
Why is understanding the origin of eukaryotes important?
The origin of eukaryotes is not merely a theoretical issue, as understanding it may help reveal how complex cellular organisation, energy-efficient metabolism and the biological complexity ultimately emerged that made the development of nervous systems, emotions and intelligence possible.
According to researchers, Asgard archaea can be found in deep-sea sediments and hot springs alike, and analysing their genomes is like travelling back in time to the dawn of life.
Biologist Valerie De Anda believes that, for the first time, we now have the opportunity to study directly the genetic foundations from which the first eukaryotic cells arose. This could fundamentally reshape everything we have so far thought we knew about the origin of eukaryotes – and what we have managed to discover up to now.