The fossil record has long been used to gather knowledge of past life on earth, but do we really know how accurate a record it is?
The fossil record has long been used to gather knowledge of past life on earth, but do we really know how accurate a record it is?
"It's a question that goes back a long way to the time of Darwin, who looked at the fossil record and tried to understand what it tells us about the history of life," says Shanan Peters, a geoscientist at the University of Wisconsin-Madison.
According to Peters and colleague Bjarte Hannisdal, in a paper published in the journal Science, the evolution of marine life over the last 500 million years has been driven by changes in marine chemistry and sea-level.
"These results tell us that the number of species in the oceans through time has been influenced by the amount and availability of carbon, oxygen and sulphur, and by sea level," says Lisa Boush, program director in the National Science Foundation's Division of Earth Sciences, which funded the research. "The study allows us to better understand how modern changes in the environment might affect biodiversity today - and in the future."
Hannisdal and Peters analysed fossil data from a period known as the Phanerozoic eon, which is the current eon, and includes the evolution of most plant and animal life. The data used reflects ancient global climates, tectonic movements, continental flooding and changes in Earth’s oxygen, carbon and sulphur cycles.
Using a method known as information transfer, they were able to identify relationships between biodiversity and environmental proxy records.
"We find an interesting web of connections between these different systems, which combine to drive what we see in the fossil record," Peters says.
An example of this is that the sulphur cycle is closely related to marine biodiversity, it was also found that sea-level is important in the history of marine biodiversity. The significant changes in marine biodiversity that are seen in the fossil, Peters says, "likely arose through biological responses to changes in the global carbon and sulphur cycles, and to sea level, through geologic time."
Despite being incomplete, the researchers believe the fossil record is a good representation of the last 500 million years of marine evolution, and the findings emphasise how connected Earth’s physical, chemical and biological processes are.
"Earth systems are all connected," says Peters. "It's important to realise that when we perturb one thing, we're not just affecting that one thing.
"The challenge is understanding how that perturbation of one thing, for example, the carbon cycle, will affect the future biodiversity of the planet."
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