Our most important source for knowledge about past life is the fossil record. But how exact is it in telling us about the history of life?

According to a new study in Science the evolution of marine life over the last 500 million years has been strongly influenced by sea level changes and ocean chemistry and despite its incompleteness, the fossil record is a good representation of marine biodiversity over this period.

Fossils and paleoenvironmental records

The researchers uncovered fossil data of the Phanerozoic eon from the Paleobiology Database. This data encompasses the evolution of most animal and plant life. They compared this data to records on continental flooding, ancient global climates, changes in biogeochemistry and tectonic movement, paying particular interest in carbon, oxygen and sulphur cycles.

To identify causal relationships instead of just general associations between these environmental proxy records and biodiversity they used a method called information transfer.

Mass extinctions and proliferations

What they found that marine biodiversity has been strongly influenced by sea level and the amount and availability of oxygen, carbon and sulphur. Even the mass extinctions and both proliferations show a strong connection between these four factors and the dramatic changes in biodiversity seen in the fossil records. But the link can also be seen at different less turbulent timescales.

The interconnectedness of things

According to the researchers the results emphasise the interconnectedness of chemical, physical and biological processes on Earth allowing a better understanding of how modern environmental changes might influence biodiversity. The challenge is understanding how a change in one factor like the carbon cycle will ultimately affect future biodiversity.

© Jorn van Dooren | www.bitsofscience.org