Curiosities Why some animals become fossils and others disappear
A Lausanne research team has solved a mystery surrounding fossils. Why do some animals become fossils while others disappear without a trace? The decisive factor is the body of the animal itself, as the research team shows in a new study.
01.05.2025, 11:04
SDA
The size and chemical composition of an animal can significantly influence whether it is preserved as a fossil for millions of years, as the University of Lausanne (Unil) announced on Thursday.
According to the study published in the journal "Nature Communications", larger and protein-rich animals have a significantly higher chance of becoming fossils. Large arthropods - animals with articulated legs such as insects, crabs or spiders - are therefore more likely to be fossilized than smaller, simply built animals such as certain flatworms or other worms that live in water.
"It is therefore quite possible that some organisms could never be preserved in fossil form and that we will therefore never be able to observe them at all or only with great difficulty," explained Nora Corthésy, lead author of the study.
Decomposition in the laboratory
Fossils are much more than just bones, the researchers emphasized. Some of the most impressive finds contained the remains of soft tissue such as muscles, intestines or even brains. However, why only some animals or organs are so well preserved has been a mystery until now.
To get to the bottom of this mystery, the research team had various animals, including shrimps, snails, starfish and worms, decomposed in the laboratory in a controlled manner. They analyzed how the chemical environment of the animals changed during the decomposition process. It was found that larger and more protein-rich animals produce a low-oxygen environment more quickly. These conditions inhibit decomposition and promote processes that are important for fossilization.
