In China, there are rocks from 590 million years ago that preserve microscopic organisms, but no animals. Therefore, it was thought that they did not yet exist. However, researchers studied more recent rocks from Mongolia. They also do not contain animals, although we know from other fossils that there were already them then.
To situate the debate, we must remember that the first animals did not necessarily have skeletons or hard parts. Many were soft-bodied organisms, difficult to preserve in the geological record. Furthermore, finding fossils depends on adequate conditions to bury and preserve them for millions of years. In many places, sediments are transformed, disappear by erosion or remain inaccessible under other layers.
This comparison is especially important because it shows that an environment capable of preserving tiny traces may not register the presence of animals, even when they already inhabit the planet. The absence of remains does not automatically amount to proof of absence.
This is how they discovered the problem: just because we don’t find a fossilized animal doesn’t mean it didn’t exist.
For years, certain estimates of the appearance of animals were based on maximum limits derived from sites without animal fossils. If those limits were too strict, they could also push the calculated dates toward more recent times.
By checking the molecular clock, which compares genetic differences and uses fossils to calculate when our evolutionary ancestors lived, they came up with a much older date: between 800 and 700 million years ago.
This method is based on the idea that accumulated differences in DNA allow us to reconstruct relationships and estimate when different lineages separated. However, its results depend on the data used and the analysis hypotheses. Therefore, the new estimates do not replace a proven fossil.
They have not found animals of that age: it is an estimate that still needs to be confirmed.
REFERENCES
Orin M. Lole Durbin, Eliel SC Anttila, Derek EG Briggs, Francis A. Macdonald, and Ross P. Anderson. “Re-evaluating molecular clock maximum age calibrations revives pre-Ediacaran divergence estimates for animals”. Science AdvancesOctober 2, 2026.
