Land plants colonize Earth 100 mln yrs earlier than previously thought

Updated 2018-02-20 10:52:02 Xinhua

A British study shows that plants colonized the land about 100 million years earlier than previously thought, which can be dated back to the middle Cambrian Period.

In a paper published on Monday in the journal Proceedings of the National Academy of Sciences, scientists from University of Bristol used the "molecular clock," which analyzes the genetic differences between living species, to help establish a more accurate evolutionary timescale.

Scientists previously thought, relying on oldest fossil plants, that land plants, the relatives of pond scum in the water, were about 420 million years old.

Jennifer Morris, from the University of Bristol's School of Earth Sciences and the co-lead author on the study, said: "The global spread of plants and their adaptations to life on land led to an increase in continental weathering rates that ultimately resulted in a dramatic decrease the levels of the 'greenhouse gas' carbon dioxide in the atmosphere and global cooling."

Plants are major contributors to the chemical weathering of continental rocks, a key process in the carbon cycle that regulates Earth's atmosphere and climate over millions of years.

"Previous attempts to model these changes in the atmosphere have accepted the plant fossil record at face value. Our research shows that these fossil ages underestimate the origins of land plants, and so these models need to be revised," Morris said.

"The fossil record is too sparse and incomplete to be a reliable guide to date the origin of land plants," sadi co-lead author Mark Puttick. "We compare differences in the make-up of genes of living species."

"These relative genetic differences were then converted into ages by using the fossil ages as a loose framework," Puttick said.

"Our results show the ancestor of land plants was alive in the middle Cambrian Period, which was similar to the age for the first known terrestrial animals," Puttick said.

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