Creatures from a world lost in billion-year-old rocks

2023-06-07 17:32:28

The artist’s imagination of a set of primordial eukaryotic organisms of the ‘protosterol biota’ inhabiting a bacterial mat on the ocean floor. – ORCHESTRATED IN MIDJOURNEY BY TA 2023

MADRID, 7 Jun. (EUROPA PRESS) –

Newly discovered biomarker signatures point to a whole range of previously unknown organisms that dominated complex life on Earth some billion years ago.

They differed from complex eukaryotic life as we know it, such as animals, plants, and algae in their cell structure and likely metabolism, that he adapted to a world that had much less oxygen in the atmosphere than today.

An international team of researchers is now reporting on this breakthrough in the field of evolutionary geobiology. in the journal Nature.

Previously unknown “protosteroids” were shown to be surprisingly abundant throughout Earth’s Dark Ages. The primordial molecules were produced at an earlier stage of eukaryotic complexity, extending the current record of fossil steroids beyond 800 to 1.6 billion years ago. Eukaryotes is the term for a kingdom of life that includes all animals, plants, and algae and is distinguished from bacteria by having a complex cell structure that includes a nucleus, as well as more complex molecular machinery.

“The highlight of this finding is not just the extension of the current molecular record for eukaryotes,” says co-author Christian Hallmann, a geochemist at the GFZ (Helmholtz Association of German Research Centers). “Since the last common ancestor of all modern eukaryotes, including humans, was probably capable of producing ‘normal’ modern sterols, the chances are high that the eukaryotes responsible for these rare signatures belonged to the trunk of the phylogenetic tree.”

This “stem” represents the common ancestral lineage that was a precursor to all still living branches of eukaryotes. Its representatives are long extinct, but details of their nature may shed more light on the conditions surrounding the evolution of complex life.

Although more research is needed to assess what percentage of protosteroids may have had an unusual bacterial source, the discovery of these new molecules not only reconciles the traditional fossil geological record with that of fossil lipid molecules, but provides insight. rare and unprecedented from a lost world of ancient life.

The competitive demise of stem-group eukaryotes, marked by the first appearance of modern fossil steroids around 800 million years ago, may reflect one of the most incisive events in the evolution of an increasingly complex life.

“Almost all eukaryotes biosynthesize steroids, such as the cholesterol that humans and most other animals produce,” adds Benjamin Nettersheim of the University of Bremen, first author of the study.

“Due to the potentially adverse health effects of elevated cholesterol levels in humans, cholesterol does not have the best reputation from a medical perspective. However, these lipid molecules are integral parts of eukaryotic cell membranes where they help in a variety of physiological functions.By searching for fossilized steroids in ancient rocks, we can trace the evolution of an increasingly complex life.”