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A study published in Science Advances on October 2, 2026, estimates that animals may have originated around 800–700 million years ago. That is a molecular-clock estimate, not the age of a newly discovered animal fossil. The oldest known animal fossils cited by Yale are about 574 million years old—so the study suggests animals could have evolved long before they appear in the recognizable fossil record.
What does the new study say about when animals first evolved?
The study’s authors estimate that animal origins may date to roughly 800–700 million years ago. Yale’s October 2026 account describes this as 100–200 million years or more before the oldest recognizable animal fossils. The range comes from molecular-clock analyses using older geological constraints; it is not a direct date for an animal found in rock.
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A molecular clock uses genetic differences among living organisms to estimate when their ancestral lineages diverged. Because the result depends in part on the dates used to calibrate the clock, choosing different geological constraints can shift the inferred origin substantially.
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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Why did the researchers revisit the fossil record?
The Weng’an question
One earlier argument used the approximately 590-million-year-old Weng’an Biota in South China as a limit on how early animals could have originated. Weng’an preserves abundant, detailed microfossils but has no definitive animal fossils. The argument was that if animals had lived by then, the site’s preservation should have captured them.
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Why an absence may not be a hard limit
The new study challenges that reasoning by pointing to the approximately 550-million-year-old Kheseen Biota in Mongolia. Yale’s account says animals were definitively known to exist by the time Kheseen formed, yet the site also lacks animal fossils despite preserving other microfossils. The authors argue that preservation conditions or ecology can leave animals missing from even an unusually informative deposit.
This weakens the use of Weng’an’s missing animal fossils as a firm maximum-age constraint. It does not show that animals lived at Weng’an, or that they lived in any of the older deposits considered by the study.
How did the study arrive at an 800–700-million-year estimate?
The authors considered three exceptionally preserved fossil assemblages dated to roughly 850–730 million years ago. Yale reports that these deposits were thought to have conditions suitable for preserving early animals, but no animal fossils have been found in them. The researchers used the assemblages’ ages as alternative maximum-age constraints in molecular-clock analyses.
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With those older constraints, the clock analyses produced the 800–700-million-year estimate. That is the authors’ modeled result and interpretation—not proof that animals are present in those formations, nor a fossil date establishing when the first animals appeared. An absence at a particular site cannot by itself establish whether animals were absent everywhere at that time.
What different kinds of evidence say about early animals
“The first animals” can mean an inferred evolutionary origin, an organism indicated by chemical traces, or the oldest animal fossil yet found. These are different kinds of evidence and do not provide interchangeable dates.
| Evidence | What it can tell us | Reported timing and limitation |
|---|---|---|
| Animal body fossils and fossil assemblages | Evidence of animals preserved at a particular place and time. | Yale gives about 574 million years ago for the oldest known animal fossils it cites. A 2024 study of animal microfossils from Brazil’s Bocaina Formation reports a weighted mean carbonate U–Pb age of 571 ± 9 million years. These dates concern fossil evidence, not necessarily the evolutionary origin of animals. |
| Chemical biomarkers | Compounds preserved in rock can support an interpretation about the organisms that produced them. | MIT’s 2025 account describes C30 and C31 steranes in Ediacaran-age rocks and evidence connecting them to demosponges. The account says the evidence supports a sponge-related biological source, but the sampled sediments place the inferred organisms only within the Ediacaran so far; more samples are needed to narrow the timing. |
| Molecular-clock estimates | Genetic differences among living organisms are used to infer when ancestral lineages diverged. | The 2026 study estimates animal origins around 800–700 million years ago under its selected older geological constraints. Such estimates can change with calibration choices and phylogenetic assumptions. |
The evidence types answer different questions. Fossils show when animals are preserved in the record; biomarkers can suggest the presence of particular lineages; clocks estimate evolutionary divergence. None should be presented as a single, definitive date for the first animal.
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How does the estimate compare with earlier molecular-clock work?
A 2024 analysis by Carlisle and colleagues estimated Metazoa—the animals as a broad group—to have originated in the early Ediacaran, Eumetazoa in the middle Ediacaran, and Bilateria in the upper Ediacaran. The authors accounted for uncertainty in phylogenetic relationships, clock models, and calibration strategies.
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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 glitchesThe 2026 study pushes the proposed animal-origin timing substantially earlier by changing the constraint strategy. The difference illustrates why molecular-clock dates are estimates shaped by the fossils, geological ages, and evolutionary relationships included in the analysis, rather than direct observations of the first animal.
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Does the study prove animals existed 800 million years ago?
No. It presents a model-based estimate, not direct fossil proof. No animal fossils from 800–700 million years ago are reported in the study summary. The authors’ argument is that the lack of animal fossils in selected older deposits should not automatically rule out an earlier origin; it does not establish that animals were present in those deposits.
Would this put animals before Snowball Earth?
Yes, if the early end of the proposed range is right. Yale’s account places the approximate theoretical beginning of Snowball Earth glaciations around 720 million years ago, so an origin estimate of 800–700 million years ago would put animal origins before that interval. The study does not establish how animals survived the glaciations or how the ice ages affected their evolution.
As Yale study co-author Derek Briggs put it, “Future discoveries are needed to refine our knowledge of the nature and timing of the earliest animal life on the planet.”
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