Saturday, October 03, 2026

New study suggests animals may have evolved vastly earlier than fossil evidence suggests

University of Oxford

image:
Ediacaran sea floor, Namibia, Southwest Africa - 543 million years ago. Credit: Museum of Natural History, University of Oxford / Mighty Fossils.
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Credit: Museum of Natural History, University of Oxford / Mighty Fossils.

Animals may have evolved up to 200 million years earlier than their first appearance in the fossil record. This is according to new research that challenges key assumptions scientists have used to date the origins of animal life.

The earliest animals may have evolved hundreds of millions of years before their first unmistakable fossils are found, according to a new study led by the University of Oxford. The findings, published today (2 Oct) in Science Advances, suggest animals may have originated deep in the Neoproterozoic Era, even before some of the most extreme ice ages in Earth's history.

The findings could transform our understanding of one of evolution's greatest mysteries: why animals seem to appear relatively suddenly in the fossil record just before the Cambrian Period (539 to 487 million years ago), despite other evidence suggesting that their evolutionary history began much earlier.

At the heart of the study is a problem with the way scientists have recently used the fossil record to set a maximum age for the origin of animals.

A roughly 590-million-year-old fossil deposit known as the Weng'an Biota in rocks of Ediacaran age in China preserves microscopic organisms in extraordinary detail, none of which are definitive animals. Scientists have therefore inferred that the first animals must have originated after Weng'an, assuming that this exceptional fossil deposit would have preserved them if they existed at this time.

How new fossils from Mongolia challenge assumptions

The research team, which included members from the University of California Berkeley, ETH Zürich, and Yale University, carried out a comprehensive survey of exceptionally well-preserved microfossils from the Kheseen Biota in Mongolia. The Kheseen Biota is more than 40 million years younger than Weng’an, even though they share some species. By this time animal fossils are known from sites elsewhere around the world, including Namibia and South China.

The researchers studied over 140 samples, including some from previously undocumented localities, and examined them using scanning electron microscopy. This revealed exquisite new microfossil species including acritarchs (tiny spherical organisms with spines and branching projections) as well as embryo-like fossils containing internal cells. Yet, despite this remarkable level of preservation, none can be confidently identified as an animal.

Senior author Associate Professor Ross Anderson (Museum of Natural History, Oxford University) said: “The Kheseen Biota breaks the argument that the exceptional microfossils of Weng'an mean we would have seen animal fossils in the assemblage had they existed at the time. The Kheseen microfossils are just as well-preserved, yet animals continue to be absent – despite the fact we know at that point they existed.”

Animals must have lived in different environments from those that preserved the fossils in the Kheseen Biota, or the chemical conditions there failed to preserve animal remains.

A hidden history of animal life

Given that the Kheseen Biota was preserved when animals were present but they are nonetheless not preserved as fossils, the researchers argue that Weng’an does not automatically qualify as evidence that no animals existed at that time and only appeared later than 590 million years ago.

Instead, they looked much further back, to several deposits dating from roughly 850 to 730 million years ago. These included the Svanbergfjellet Formation (Norway), Bitter Springs Group (Australia) and Chuar Group (Arizona, USA) - all fossil-rich deposits with the potential to preserve animals, even though they have eluded discovery. These deposits have previously been used as maximum dates for the origin of animals.

Using these older geological constraints, the researchers used a technique called molecular clock analysis. This method compares genetic differences between living species and, using dates from the fossil record as reference points combined with rates of evolution, works backwards to estimate when their ancestors lived. Compared with analyses constrained by the younger Ediacaran Weng’an deposit, this approach shifted the estimated origin of animals backwards by around 200 million years, to between 800 and 700 million years ago.

There are already clues that such a hidden history exists. Chemical fossils, or biomarkers, preserved in ancient rocks provide evidence consistent with sponges living at least 650 million years ago, tens of millions of years before the oldest definitive macroscopic animal fossils.

These early animals would have been small and soft-bodied, without the shells, bones or other hard structures that make later animals easier to preserve. Whether such creatures were fossilised depended on their environment and on an unusual combination of chemical conditions after death.

Could animals pre-date Snowball Earth?

An origin between 800 and 700 million years ago raises striking possibilities: animals may already have evolved before Earth entered some of the most extreme ice ages in its history or even appeared during that inhospitable interval.

During the Cryogenian Period, which began around 720 million years ago, enormous glaciers spread across the planet in episodes commonly known as Snowball Earth. The study reopens questions about whether the conditions associated with Snowball Earth played a role in the origin and early evolution of animal life.

First author, PhD student Orin Lole Durbin (University of Oxford undergraduate at the time of the study, now at Virginia Tech) said: “Pre-Ediacaran animal body fossils still elude us, and this analysis does not prove that animals existed 800 million years ago. However, our new fossil evidence from Mongolia undermines one of the main arguments for restricting animal origins to the Ediacaran interval. Meanwhile, our molecular-clock analyses show how much further back their evolutionary history could extend.”

The researchers say that future work should explore fossil deposits from different parts of the world, representing different environments and modes of fossilisation, in the search for animals. This should also consider all available evidence for animals, including body fossils, traces of their activity and chemical biomarkers.

Professor Anderson added: “Until that evidence becomes available, the precise birth date of the animal kingdom remains uncertain.”

Notes to editors:

For media enquiries and interview requests contact Associate Professor Ross Anderson: ross.anderson@oum.ox.ac.uk

The study ‘Re-evaluating molecular clock maximum age calibrations revives pre-Ediacaran divergence estimates for animals’ will be published in Science Advances at 19:00 BST / 14:00 ET Friday 2 October 202, DOI 10.1126/sciadv.aeg6289. To view a copy of the paper before this under embargo, access the Science Advances press pack https://www.eurekalert.org/press/vancepak or contact: vancepak@aaas.org

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Journal

Science Advances

DOI

10.1126/sciadv.aeg6289

Article Title

Re-evaluating molecular clock maximum age calibrations revives pre-Ediacaran divergence estimates for animals

Article Publication Date

2-Oct-2026

Estimated timeline for the origin of animals based on molecular clock analyses. The grey bar on the right of the image is the origin of animals based on an Ediacaran upper calibration. The grey bar to the left is the origin based on older deposits in the Tonian period, as suggested by the new study. Credit: Orin Lole Durbin.

Credit

Orin Lole Durbin.

CaptiAsterocapsoides wenganensis, Kheseen Formation, latest Ediacaran/early Cambrian. Scale bar: 0.1 mm. Credit: Derek Briggs.

Knollisphaeridium maximum, Kheseen Formation, latest Ediacaran/early Cambrian. Scale bar: 0.1 mm. Credit: Derek Briggs.

Study author Associate Professor Ross Anderson (University of Oxford) in the mountains to the west of Lake Khuvsgul, Mongolia during fieldwork in summer 2017. Credit: Ross Anderson.

UB researchers grow salivary glands from pluripotent stem cells

Promising solution for cancer patients and people with Sjögren’s disease that hinders saliva production

University at Buffalo

BUFFALO, N.Y. — Extreme dry mouth, caused by radiation for cancer treatment and autoimmune diseases such as Sjögren’s disease, radically affects quality of life for sufferers. It can hamper speaking, swallowing and eating, and for years has seemed an intractable problem.

Attempts to stimulate the salivary glands to produce more saliva or to create artificial saliva have been ineffective.

Now, a small team of University at Buffalo researchers is working on a promising new strategy: creating salivary glands from human pluripotent stem cells (PSC) that could ostensibly be implanted into an individual’s mouth.

“Human pluripotent stem cells can be derived from easily accessible adult somatic cells, such as skin or blood cells, making them an attractive cell source for therapeutic applications,” says Stelios Andreadis, PhD, SUNY Distinguished Professor in the Department of Chemical and Biological Engineering in the School of Engineering and Applied Sciences at the University at Buffalo.

Andreadis is the co-principal investigator (PI) on the study that was published Sept. 17 in the journal Nature Communications. The co-PI is Olga Baker, PhD, DDS, a professor in the Department of Otolaryngology at the University at Missouri School of Medicine, in Columbia.

Laura Sherwood, PhD candidate in biomedical engineering and member of Andreadis’s research group, was the first author on the paper, along with Ronel Samuel, who graduated with his PhD in 2024. Last year, Sherwood earned an award for her research on this topic, which she presented at the 2025 Salivary Glands and Exocrine Biology Gordon Research Conference.

Andreadis explains that they are guiding these stem cells through steps that are similar to how salivary glands form during human development. They gradually produce salivary gland epithelial progenitor cells (SGEPs), which organize themselves into tiny, three-dimensional structures called organoids, or mini organs.

“Our findings suggest that salivary gland organoids may hold promise for studying salivary gland development, disease progression and drug screening, as well as for development of cell therapies for salivary gland regeneration,” says Andreadis, who also serves as director of UB’s Center of Cell, Gene and Tissue Engineering and is a member of the UB Center of Excellence in Bioinformatics and Life Sciences.

In 2012, Japanese stem cell researcher Shinya Yamanaka and the late British biologist John Gurdon were awarded the Nobel Prize for their discovery that mature human cells can be converted to pluripotent stem cells. These cells have the potential to become almost any type of cell in the body.

“These cells have since been used to create vascular cells, brain cells and kidney cells, but they have not yet been successful with the salivary glands,” Andreadis says.

Baker’s research team in Missouri transplanted the organoids into the submandibular salivary glands of immunodeficient mice, which allowed the human-derived tissue to be studied without immune rejection. Andreadis and the UB team then performed the immunostaining and analyzed how well the transplanted organoids integrated and differentiated within the host tissue.

They discovered that after more than 40 days in mice, the transplanted organoids not only survived but also integrated into the existing salivary gland tissue. Further analysis showed that the organoids contained cells that are present in more mature glands, including acinar cells, which produce saliva; ductal cells, which carry saliva to the mouth; and myoepithelial cells, which help squeeze saliva out of the glands.

“These newly formed glands looked similar to native salivary glands and even developed lumens, or the hollow spaces where saliva would normally flow,” Andreadis says.

The team plans to further refine the differentiation process so that the cells comprising the organoids become more mature and their developmental fate can be more precisely controlled.

“Basically, our experiments so far showed that the transplanted organoids have the potential to survive in vivo,” Sherwood says. “They integrated with the gland of the mouse and differentiated to include major salivary gland structures. This means they could, potentially, become a renewable source of replacement cells in patients in the future.”

The team is also working to determine the best stage of organoid development for transplantation and to improve the conditions in which the organoids grow. The goal is to help them produce more saliva and connect properly with the existing ducts that carry saliva to the mouth, as well as with the nerves that control salivary gland function.

“While using these cells in humans is a long way off, this research does suggest that one day scientists could repair salivary glands damaged by radiation therapy, restore saliva production in people with chronic dry mouth, study diseases of the salivary glands in the lab and test potential new drugs on human salivary tissue,” Andreadis says.

Other participating researchers in this study included graduate student Sai Harsha Bhamidipati in the UB Department of Chemical and Biomedical Engineering; Kihoon Nam, Frank Maslow and Travis Small, with the University of Missouri; and Yali Zhang, Jianmin Wang, and Song Liu, with the Department of Biostatistics and Bioinformatics at Roswell Park Comprehensive Cancer Center.