Scientists have discovered an ancient organism called “Asgard” in the hypersalten waters of Shark Bay, Australia, which contains microbes that provide a centuries-long evolutionary puzzle – how did simple, single-celled bacteria evolve into complex multicellular organisms, animals and humans? These unique microorganisms act as an evolutionary link; They carry with them cellular machinery that is thought to be unique to complex cells, illustrating an evolutionary turning point in evolution.
Protozoan eukaryotes, which we now call “living fossils,” represent those specific protozoan microorganisms that can exist and consume other protozoan microorganisms. This led to the creation of the first eukaryotic cell. Without this unique microscopic ancestor found in the hypersaline basins of Australia, the branch of the evolutionary tree that is humanity could not have evolved.
A microbe found in Australia reveals the secret of our existence
According to the study published in the journal Nature, the identification of Asgard archaea, which were discovered in microbial mats at Shark Bay, shows that these are the closest living relatives of eukaryotes, or organisms that are eukaryotes in their cells, including humans. Asgard archaea contain so-called “eukaryotic signature proteins” (ESPs), which provide molecular scaffolding for intracellular structure. DNA analysis indicates that Asgard archaea represent a eukaryotic ancestor, establishing a direct evolutionary lineage between this single-celled organism and modern humans.
How endosymbiosis fueled the emergence of multicellular life
Research on Asgard archaea supports the endosymbiosis theory.
According to this theory published in the journal PNAS, endosymbiosis begins with an Asgard-like organism ingesting some unrelated bacteria. Instead of digesting these bacteria, the larger Asgard-like cell and the bacteria were found together as symbionts. Over millions of years, engulfed bacteria gradually evolved and became what we now refer to as mitochondria – the “engine” of our cells, providing the metabolic mutation necessary for evolution to produce multicellular organisms.
How the Asgard archaea bridge the two-billion-year gap
The fascinating microbial mats and living stromatolites at Shark Bay may very well be responsible for its World Heritage status, and they are truly amazing because they are found in twice as much salt as in the open ocean. The ancient environment in which they live resembles the oceans that existed two billion years ago, allowing scientists to see a current version of the conditions that gave rise to complex life through the Asgard archaea that now live in this specific ecological niche and are considered “missing links” because they show evolutionary plasticity.
The hidden complexity of simple microbes
In addition, Asgard archaea have a unique cytoskeleton compared to standard prokaryotic cells; This enables the cell to change shape and move, and perhaps transport materials internally, that were previously thought to be only associated with complex life forms, according to the Journal of Molecular Biology. Thus, they provide evidence that the cellular biomechanics necessary for complex, environmentally dependent life forms existed before the first animals appeared.
