Animal life may be 200 million years older than its fossils suggest
molecular-clock analysis
A method that estimates ancestor dates from genetic differences, fossil dates, and change rates.
Weng'an Biota
A Chinese fossil deposit about 590 million years old.
Cryogenian Period
A period beginning around 720 million years ago, with extreme global ice episodes.
What happened
Animal life may have begun between 800 and 700 million years ago. That is about 200 million years earlier than some earlier estimates. A team led by the University of Oxford, a British university, reached this estimate by rethinking how fossil sites set age limits. The study appeared in Science Advances, a research journal. Read the paper
It does not report an animal body fossil from 800 million years ago.
The old puzzle
Clear animal body fossils reach back only about 574 million years. Then animals seem to appear suddenly near the Cambrian Period, which lasted from 539 to 487 million years ago. Other clues suggest a longer history. These include genes and chemical fossils.
The Weng'an Biota in China is about 590 million years old. It preserves tiny fossils in remarkable detail. None is definitely an animal. Scientists once treated this absence as a maximum age. They assumed animals would have left fossils there if they already existed. That assumption placed animal origins after Weng'an.
The Mongolian test
Researchers examined the Kheseen Biota in Mongolia. It is more than 40 million years younger than Weng'an. By then, animal fossils were known from other places. The team studied more than 140 samples with scanning electron microscopy. They found tiny spiny fossils and embryo-like fossils with internal cells. Still, none could be confidently identified as an animal.
This result weakens the old argument. A well-preserved fossil site can still miss animals. The animals may have lived in another environment. Chemical conditions after death may also have prevented fossilization.
How the estimate moved
Next, the team used older deposits from roughly 850 to 730 million years ago. They came from Norway, Australia, and Arizona. These rocks contain many fossils, but no confirmed animal bodies. Researchers considered them possible limits for animal origins.
They then ran a molecular-clock analysis. This method compares genetic differences among living species. It also uses fossil dates and estimated evolutionary rates. The method works backward to estimate when shared ancestors lived. Using older limits moved the estimate back about 200 million years. It reached 800 to 700 million years ago.
Chemical fossils offer another clue. They suggest sponge-like animals lived at least 650 million years ago. That clue does not show exactly when all animals began. It supports the possibility of a much older history.
Why it matters
If this range is right, animals may predate or overlap the Cryogenian Period. That period began around 720 million years ago. It included episodes called Snowball Earth, when glaciers spread across the planet. The study therefore reopens questions about ice, animal origins, and early evolution.
It also changes how scientists read empty fossil layers. A missing animal fossil may reflect habitat or preservation chemistry. It does not automatically mean animals were absent.
What remains unknown
The researchers stress that the analysis is not proof. No pre-Ediacaran animal body fossil has been found. The exact birth date of animals remains uncertain. Scientists still do not know where those early animals lived. They also need to test whether preservation conditions explain the gap.
Future work will examine older rocks from more environments. Researchers will combine body fossils, activity traces, and chemical biomarkers. The key question is whether new evidence confirms an early origin or moves the date again. Oxford summary
Could animals have lived long before their fossils?
📰 Full story: Animal life may be 200 million years older than its fossils suggest
Animals may have begun hundreds of millions of years before clear fossils appeared.
Weng'an Biota
A Chinese rock deposit holding tiny fossils from about 590 million years ago.
Kheseen Biota
A Mongolian fossil deposit more than 40 million years younger than Weng'an.
molecular clock
A method that estimates old dates by comparing genetic changes and fossils.
💡 The gist
- Animals may have started 800–700 million years ago.
- That is about 200 million years earlier than some estimates.
- Missing fossils do not prove animals were absent.
A team led by the University of Oxford (a British university) studied this puzzle. The paper appeared in Science Advances. Scientists wanted to know if old fossils set the right age limit.
A maximum age is the oldest date a method allows. It is not the date animals definitely began.
The Weng'an Biota (a Chinese fossil deposit) is about 590 million years old. Its tiny fossils are preserved very well. None is clearly an animal. Scientists once made a simple assumption. If animals lived then, Weng'an should show them. They placed animal origins after Weng'an.
The team tested that assumption in Mongolia. The Kheseen Biota is more than 40 million years younger. Animals were already known elsewhere at that time. Researchers examined more than 140 samples. They used a scanning electron microscope. The samples included tiny fossils with spines. Some looked like embryos with inner cells. Still, none was clearly an animal.
This matters because good preservation can miss animals. The animals may have lived somewhere else. Chemistry after death may also have erased their bodies.
The researchers then used older rocks. These rocks came from 850–730 million years ago. They came from Norway, Australia, and Arizona. The team used a molecular clock. It compares genetic differences in living species. It also uses fossil dates and change rates. The calculation estimates when ancestors lived. It moved animal origins back about 200 million years.
Chemical fossils offer another clue. They suggest sponge-like animals lived at least 650 million years ago. That clue does not show exactly when all animals began. It supports the possibility of a much older history.
That date could place animals before or during Snowball Earth. The Cryogenian Period began around 720 million years ago. Huge glaciers spread during some of its episodes. The study does not prove animals lived then. No animal body fossil that old has been found.
Next, scientists will search different ancient environments. They will look for bodies, activity traces, and chemical clues. These findings may confirm or change the proposed date.
Could animals have lived in the very old past?
📰 Full story: Animal life may be 200 million years older than its fossils suggest
Their soft bodies may have vanished before fossil records formed.
University of Oxford
A British university that led this research.
Kheseen Biota
A group of very old fossil rocks in Mongolia.
molecular clock
A way to guess old dates from changes in living things.
What happened?
Long ago, Earth may already have had animals. Their bodies may have been tiny and soft. Soft bodies do not become fossils easily. So their remains can disappear.
The University of Oxford, a British research university, led the study. Scientists looked at the Kheseen Biota in Mongolia. It is a group of very old fossil rocks. They found many tiny life shapes. None could be called an animal. But animals lived in other places then. So a missing fossil does not prove absence.
Scientists used a molecular clock. It compares changes in living things. This method pointed to 800–700 million years ago. That is about 200 million years earlier. The study is still an estimate. No animal body that old has been found. Scientists will search older rocks and animal tracks. The animal kingdom’s first day is still unknown.