Recent groundbreaking research published in the prestigious journal Nature has revealed fascinating insights about the origins of complex life forms on Earth. Scientists from The University of Texas at Austin and other institutions have analyzed the genomes of various archaea microbes and made a remarkable discovery: eukaryotes, which include all plants, animals, insects, and fungi, share a common ancestor with the archaea microbes, specifically those belonging to the Asgard group.
This finding establishes eukaryotes as a distinct and well-nested clade within the Asgard archaea, much like birds are a subgroup within the larger group of dinosaurs. The researchers identified a newly described order of archaea, called the Hodarchaeales or Hods for short, as the closest microbial relative to all complex life forms on the tree of life. These Hods are part of the Asgard archaea, which evolved over 2 billion years ago and continue to exist today.
While no fossils of eukaryotes older than approximately 2 billion years have been found, the existence of a common Asgard archaean ancestor suggests that prior to that period, only various types of microbes inhabited the Earth. Understanding the evolutionary events that led to the emergence of eukaryotes is a significant challenge, and the discovery of this common ancestor represents a significant step in unraveling that mystery.
The research team, led by Thijs Ettema of Wageningen University, expanded the known genomic diversity of the Asgard group by adding over 50 previously unknown Asgard genomes to their analysis. Through their study, they found that the ancestor of all modern Asgards likely thrived in hot environments, obtaining sustenance from CO2 and chemicals. In contrast, the Hods, which are more closely related to eukaryotes, exhibit metabolic similarities to complex organisms like us, as they consume carbon and inhabit cooler environments.
To glean information about the Asgard archaea, scientists collect genetic material from the environment and piece together their genomes. Although only two strains of Asgards have been successfully cultivated in the lab so far, genetic similarities to other organisms that can be studied in controlled settings help infer their metabolic characteristics and other traits.
The researchers’ approach can be likened to a metaphorical time machine, allowing them to delve into the potential metabolic reactions that might have triggered the advent of complex life. Instead of relying on fossils or ancient artifacts, they examine the genetic blueprints of present-day microbes to reconstruct their evolutionary past.
The implications of this research are profound. By uncovering the molecular blueprints of the ancestral cells that gave rise to eukaryotes, scientists are gaining valuable insights into the origins of complex life on our planet. This discovery has prompted playful references to Norse mythology, with some researchers humorously declaring that “We are all Asgardian,” underscoring the connection between our shared ancestry and the legendary city of Asgard.
Source: University of Texas at Austin