D uring the first 4 billion years of Earth’s history, our planet’s continents would have been devoid of all life except for microbes . All this changed thanks to the origin of terrestrial plants, dyeing the continents green and creating habitats that animals would later invade, leaving the sea. And we believed that this moment had occurred around 420 million years ago. Now, new research by scientists at the University of Bristol (UK) has discovered that the first plants adapted to terrestrial life appeared around 500 million years ago.
The study, published in the journal Proceedings of the National Academy of Sciences (PNAS), indicates that this event occurred about 100 million years earlier than previously believed , changing the perception of the evolution of the Earth’s biosphere.
Plants are crucial elements in the evolution of the planet, as they have contributed to the chemical wear of continental rocks, a very relevant process in the carbon cycle that has regulated the atmosphere and the Earth’s climate over millions of years.
Dating
The team of scientists used the “molecular clock” methodology, which combined evidence of genetic differences between living species and fossils in their shared ancestors, to establish an evolutionary time scale that sees through gaps in the fossil record. , that is, it analyzes genetic differences to establish a more precise period of evolution.
“The global spread of plants and their adaptations to life on land led to increased rates of continental weathering (alteration of rocks in their natural state) that ultimately resulted in a dramatic decrease in carbon dioxide levels of greenhouse gas in the atmosphere and global cooling, “explains Jennifer Morris, co-author of the work.
Thus, research shows that previous fossil ages underestimate the origins of terrestrial plants, so these evolutionary models should be reviewed.
“ The fossil record is too sparse and incomplete to be a reliable guide for dating the origin of land plants. Rather than relying solely on the fossil record, we use a ‘molecular clock’ approach to compare the differences in the genes of living species: these relative genetic differences were then converted into ages by using fossil ages as a flexible framework, “says Mark Puttick.
In light of the results, the ancestor of land plants was alive in the Middle Cambrian Period. “ Our results show that the ancestor of living plants already existed in the Middle Cambrian period, somewhat similar to the age of the first known land animals,” Puttick said.
A difficulty posed in this type of study is that the relationships between the first terrestrial plants are not known, hence different assumptions about the relationships between terrestrial plants were used. The surprise was to discover that this did not affect the age of the first land plants.
“Any future attempt to model atmospheric changes in deep time must incorporate the full range of uncertainties that we have used here,” the authors state.
Reference: Jennifer L. Morris el al., “The timescale of early land plant evolution,” PNAS (2018). www.pnas.org/cgi/doi/10.1073/pnas.1719588115
Image credit: Natural History Museum, London
