Scientists have discovered an archaea called ‘Asgard’ in the extremely high salinity waters of Australia’s Shark Bay, containing microorganisms that provide a long-standing evolutionary puzzle spanning many centuries – how did simple, single-celled bacteria evolve into such complex multicellular organisms, animals and humans? These unique microorganisms act as an evolutionary link; They carry with them cellular machinery considered unique to complex cells, thus showing us evolutionary transition points in development. The proto-eukaryote, which we now call a ‘living fossil’, represents a specialized early microorganism that could survive and consume other early microorganisms. This led to the formation of the first eukaryotic cell. Without this unique, microscopic ancestor found in the extreme saline basins of Australia, the branch of the evolutionary tree representing humanity would never have evolved.

A microbe found in Australia reveals the mystery of our existence

The identification of Asgard Archaea discovered in Shark Bay microbial mats suggests that these are eukaryotes, or the closest living relatives of eukaryotic organisms in their cells, including humans, according to the study published in Nature. Asgard archaea contain what are called ‘eukaryotic signature proteins’ (ESPs), which provide molecular scaffolding for intracellular architecture. DNA analysis shows that Asgard archaea represent a eukaryotic ancestor, establishing a direct evolutionary lineage between this unicellular organism and modern humans.

How endosymbiosis led to the rise of multicellular life

Research involving Asgard archaea supports the endosymbiotic theory. According to this theory, published in PNAS, endosymbiosis begins with an asgard-like organism ingesting some unrelated bacteria. Instead of digesting these bacteria, the large asgard-like cell and the bacteria existed together as a symbiote. Over a period of millions of years, engulfed bacteria gradually evolved to become what we now refer to as mitochondria – the ‘engines’ of our cells, providing the metabolic boost necessary for evolution to produce multicellular organisms.

How Asgard archaea bridge a two-billion-year gap

The remarkable microbial mats and living stromatolites in Shark Bay may very well be responsible for its World Heritage status and are truly spectacular as they exist in twice as much salt as the open oceans. The ancient environment in which they live resembles the oceans of 2 billion years ago, allowing scientists to see a present-day version of the conditions that gave rise to complex life through the Asgard Archaea that now live in this particular ecological region and are considered the ‘missing link’ because they exhibit evolutionary plasticity.

The hidden complexity of simple microbes

Additionally, Asgard archaea have a unique cytoskeleton compared to standard prokaryotic cells; According to the Journal of Molecular Biology, this enables the cell to change its shape and move, and possibly transport materials internally, which was once thought to be associated with complex forms of life. Thus, they provide evidence that the cellular biomechanics that are essential for complex, environment-dependent life forms existed before the appearance of the first animals.