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1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitchesA 2026 molecular-clock study supports an estimate that animals originated roughly 800–700 million years ago, before the Ediacaran Period. The result depends on which fossils are used to set the clock’s maximum age limits: it is a model-based estimate, not evidence that animal body fossils from that time have been found.
What does the study estimate about when animals first evolved?
The analyses support a late Tonian to mid-Cryogenian origin for Metazoa—the animal kingdom—at approximately 800–700 million years ago. That interval is an estimate conditional on the study’s models and calibration choices, not a precise date or a newly discovered fossil record.
The paper, by Orin M. Lole Durbin, Eliel S.C. Anttila, Derek E.G. Briggs, Francis A. Macdonald, and Ross P. Anderson, was published in Science Advances on October 2, 2026, as volume 12, issue 40, article eaeg6289 (DOI: 10.1126/sciadv.aeg6289). Its central question is whether the Ediacaran Weng’an Biota provides a dependable maximum-age calibration for animal origins.
Why does the Weng’an Biota matter for molecular clocks?
How a maximum calibration constrains a clock
Molecular clocks use differences among living organisms’ DNA, together with a model of how those differences accumulate over time, to estimate when lineages diverged. Fossils help anchor that timeline. A maximum-age calibration is an upper limit: it constrains how far back a lineage’s origin can be placed. The choice of such limits can substantially affect both the accuracy and precision of the resulting dates.
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Why the Weng’an fossil absence is being questioned
The Weng’an Biota of China is an Ediacaran assemblage used as a candidate maximum calibration. The study compares it with Mongolia’s Kheseen Biota, which has similar preservation and microfossil assemblages. Neither assemblage contains definitive animal fossils, but the Kheseen Biota dates to approximately 550–526 million years ago, when animals were already present.
That comparison makes the absence of animal fossils at Weng’an less decisive as evidence that animals had not yet evolved. A deposit can fail to preserve organisms that existed at the time, or its ecology may not capture the organisms a researcher is looking for. An absence in a deposit younger than known animals elsewhere therefore cannot, by itself, securely set an upper bound on when animals originated.
The comparison challenges the reliability of treating Weng’an as a maximum calibration; it does not show that Weng’an is unusable under every model or calibration strategy. The broader point is that a fossil absence is an uncertain basis for ruling out an earlier origin.
How do fossils, biomarkers, and molecular clocks differ?
These evidence types address animal history in different ways. The ages below are the figures reported in the 2026 study abstract or its Dryad data record; they should not be read as equivalent observations.
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Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →| Evidence | What the study reports | What it establishes |
|---|---|---|
| Animal body fossils | The Dryad research-data abstract describes the body-fossil record as extending to about 574 million years ago. | Direct fossil evidence reaches that point in the record; it does not establish that animals originated then. |
| Lipid biomarkers | The same 2026 abstract says biomarkers suggest animal origins before 635 million years ago. | They provide a chemical line of evidence for an earlier origin, distinct from animal body fossils; the date is not presented as a universally settled origin. |
| Molecular-clock estimate | The paper and Dryad abstract report an approximately 800–700-million-year estimate when older deposits are used as maximum-calibration candidates. | This is a model-based divergence estimate, conditional on the calibration and analysis—not a fossil observation. |
The difference between the body-fossil record and the earlier estimates is not necessarily a contradiction. A lineage can exist before its fossils are found, while chemical signals and molecular-clock models have their own interpretive limits.
Could animals have evolved before the Ediacaran?
Yes: the study’s analyses support that possibility, placing the estimated origin before the Ediacaran. Their implication is that animal lineages may have had a longer hidden evolutionary history than the currently known body-fossil record shows. The comparison with Kheseen helps explain why the absence of definitive animal fossils in an older deposit cannot alone rule out that possibility.
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Does this study prove animals existed 800 million years ago?
No. The approximately 800–700-million-year interval is the outcome of molecular-clock analyses under particular calibration choices. It is not proof that animals were present at a specific point within that interval, and it is not evidence of an 800-million-year-old animal fossil. The paper’s abstract and data record report an interval rather than a single exact birth date.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What can readers check in the study’s data?
The Dryad repository, published August 20, 2026, provides inputs, configurations, and outputs for the calibration-sensitivity analyses conducted with MCMCTree in PAML. Its files include scenario archives, molecular alignments, tree and calibration inputs, configuration and output files, and documentation for model variants. Those materials are intended to support reproducibility and independent evaluation of how changing calibrations affects the results.
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