What were the first animals to inhabit the land

For decades, scientists have discussed one of the most fundamental questions of our existence: What was the first animal that inhabited the earth? Traditional fossils, with their bones and shells, only take us to “Cambrian explosion“, about 541 million years ago, when complex life seemed suddenly. But a new study He has found The irrefutable test in much older rocks, one “fingerprint“Chemistry that not only identifies our most remote ancestors, but confirms that they were here long as we thought. And no, they had no claws, no eyes, no skeleton. They were sponges.

The study. A GEOCIENTIFIES TEAM has published in pnas The finding of fossil molecules never seen before acting as an unequivocal biological firm. This discovery ends a long controversy and reinforces the idea that demosa type of soft body sponge, were the pioneers of the animal kingdom In the neoproterozoic oceans.

Chemical fossils. To find the first animal, you have to look for more subtle clues than a skeleton. You have to look for biomarkers: the molecular remains that organisms leave behind them and that can be preserved during eons.

One of these biomarkers is Esterano C30 that was discovered a decade ago in neoproterozoic rocks. This molecule is a fossil derivative of sterols that produce modern demos, which made them the main suspects.

However, the scientific community remained skeptical. Could these molecules have been created by other organisms, such as algae, or even by geological processes that had nothing to do with life? The doubt persisted, and the identity of the first animal continued in the air.

New biomarkers. The answer to the question has come thanks to the discovery of two new and rare biomarkers: the C31 mats, specifically on 24-N-Butil Colestane (24-NBC) and on 24-SEC-Butilcolestano (24-SECBC).

The crucial thing is not only to have found them, but to have found them with the already known Esterano C30. This coexistence pattern is the key, and to be able to demonstrate the scientists carried out a real detective work, building a case with three lines of evidence that support each other.

The evidence in the rock. Analyzing samples of ancient rocks from Oman, Siberia and India, the scientists found a consistent pattern. Those rocks of EDIACARIC PERIOD (between 635 and 541 million years old) that were rich in the sponage biomarker C30 also contained significant amounts of the new C31 biomarker, especially 24-SECBC.

In the sponge. As a second evidence, the team analyzed numerous species of modern demos. They discovered that those that produce large amounts of the precursors of Esterano C30 also manufacture the precursors of the stereo C31. This coincidence between fossil and living organism is a direct and very powerful connection to reach a very clear conclusion.

In the laboratory. To demonstrate that these molecules could only have a specific biological origin, scientists synthesized eight possible isomers of the precursors of the stereo C31. Then, they were subject to processes that mimic fossilization.

The result was clear: only two of them became the exact structures of 24-NBC and 24-SECBC found in the rocks. This rules out a random or geological origin and confirms that they are the product of a very specific biological machinery, that of the sponge.

Why a sponge. This finding firmly places the origin of animals long before the famous Cambrian explosion. Sponges fit perfectly into the role of being the pioneering animal on our planet. It should be noted that they are muticellular organisms, but very simple: they are essentially cell colonies that cooperate with each other without forming tissues or complex organs. They represent the first logical step From the unicellular life with Lucatowards the complexity of the animal kingdom.

This discovery not only lets us see that the sponges were the first animal that arose, but helps us to understand the as. Keep in mind that life appeared on Earth about 3.8 billion years ago and consisted only of unicellular organizations. From here the evolution led to the transition to the multicellularity that was a monumental event, and now we know that the sponges were the protagonists.

Thanks to this molecular “fingerprint”, scientists have not only solved an old debate, but have opened a new door. Now you can search for this dual chemical (C30 + C31) in even older rocks, further refining the date of birth of the Animalia kingdom and revealing the first chapters of our own evolutionary history.

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