How Earth's axis influences evolution - and extinction

Regular changes in the Earth's orbit and axis of rotation have caused significant changes in both the evolution and extinction rates, a new study has found. Photo / 123RF

Changes in our planet's orbit have influenced evolution - and extinction - over hundreds of millions of years, New Zealand researchers have helped reveal.

The findings - made by Victoria University's Professor James Crampton and researchers from GNS Science and the Universities of Wisconsin, California Riverside, and Chicago - also hold important implications for what climate change may bring.

The research team investigated the fossils of graptoloids, an extinct type of plankton that floated in ancient oceans, and found that regular changes in the Earth's orbit and axis of rotation in turn caused significant changes in both the evolution and extinction rates of these creatures.

"This research is very exciting, because the relationship between these orbital changes and extinction has never been shown before in truly ancient ecosystems," Crampton said.

There was a strong debate in science about what impacts environmental change had on extinction and evolution, as opposed to how species themselves interacted and competed.

"With this study we can provide evidence of the impact of environmental changes on life on Earth," he said.

"The evolution cycle changes we see occurred relatively soon after the first evolution of complex ecosystems, and during one of the greatest bursts of biodiversity increase in the history of life."

Normally, changes in the Earth's orbit are something studied by astronomers, rather than palaeontologists.

"Astronomers can clearly calculate changes in Earth's orbit about 50 million years into the past, but beyond that point the calculations become impossible due to the effects of what we call chaos theory, which makes the calculations too complex to complete," Crampton said.

"But we can see the effects of changes in Earth's orbit in the fossil record, so we can provide information to astronomers that they previously couldn't find out."

Understanding the evolution of plankton was also crucial to understanding life on Earth today.

"Plankton living in the oceans today absorb a large amount of our CO2 output, keeping it out of the atmosphere," Crampton said.

"They are also an important part of the food chain. The evolution and extinction of plankton can have a large effect on marine life."

Crampton and his colleagues now planned to look deeper into the specific causes of extinction.

"We know that changes in Earth's orbit affects extinction and evolution," he said.

"What we're missing is the information in the middle – what was happening on Earth as a result of orbital changes that caused extinction or evolution."

Other research teams around the world were trying to extract sufficiently detailed information about climate change between 400 and 500 million years ago so that we can figure out exactly what the relationship is between climate changes and the plankton.

"We also want to look more closely at what happens after a species becomes extinct," Crampton said.

"We know that when a species becomes extinct a new species will evolve to take the place of the extinct species in an ecosystem, but we don't know how long that takes."