Complex life evolved on Earth 100 million years AFTER previously thought, scientists say

The first signs of complex multicellular life evolved on Earth about 100 million years after first thought, according to scientists studying chemical biomarkers.

Researchers from the Australian National University (ANU), Max Planck Institute and Caltech say the discovery has big implications for our understanding of evolution.

An MIT study in 2009 claimed that early complex life evolved 635 million years ago, based on traces of chemicals found in Oman rocks up to that time.

The chemicals found in the rocks – including steroids – were remarkably similar to the chemicals produced by modern sponges and thus were assumed to be biomarkers for complex life.

A team of chemists was able to recreate the same “biomarkers” in a laboratory using common algae, widely found on Earth during this period.

The animals diversified rapidly and became ecologically dominant in the early Cambrian period (541-485 million years ago) – however scientists believe the first animals were born long before this based on molecular data.

Many suspect they would have emerged during the Neoproterozoic era (1,000-541 million years ago), although the exact timing remains controversial.

The oldest and most uncontested animals in the fossil record are found in deposits from 558-552 million years ago during the Ediacaran period and others, with “some degree of confidence,” have been traced back to 571 million years ago.

However, most molecular clocks place the appearance of animals in the range of 900-635 million years ago, during the cryogenic or Tonic periods.

The researchers used “biomarkers” to try to bridge this 340-million-year gap between the molecular clock and actual fossil evidence.

This is what the MIT team did in 2009 when they found “evidence” of a sponge biomarker in rocks dating back 635 million years – but new research has found that those biomarkers could be produced by other mechanisms, not only. sponges.

“It brings the oldest animal evidence of nearly 100 million years closer to the present day,” said Dr. Lennart van Maldegem, co-author of one of two related studies on the potential origins of biomarkers in these ancient rocks.

‘We were able to demonstrate that some common algae molecules can be altered by geological processes, leading to molecules that are indistinguishable from those produced by sponge-like animals.’

This brings the earliest “confirmed” date for the beginning of complex life on Earth to be about 560 million years ago, to sponges that lived during the Cambrian era.

The mystery of when our very first animal ancestors emerged and became abundant in the oceans has puzzled paleontologists for more than a century.

‘Ten years ago, scientists discovered molecular fossils of an animal steroid in rocks that once lay at the bottom of an ancient Middle Eastern sea,’ said Professor Jochen Brocks, co-author of the study.

“The big question was: how could these sponges have been so abundant, covering much of the seafloor around the world, but leaving no body fossils?”

Dr Ilya Bobrovskiy, lead author of the other study, said the researchers were able to “solve this mystery” by recreating the steroid markers in the laboratory.

“While he argues that true sponges are the only living organism capable of producing these steroids, chemical processes can mimic biology and transform common and abundant algae sterols into ‘animal’ sterols,” he said.

‘These molecules can be generated in the laboratory when simulating geological weather and temperatures, but we have also shown that such processes occurred in ancient rocks.’

The two studies were published in Nature Ecology and Evolution.