The landmass on Earth did not have any life for the first 4 billion years of its history, except for microbes. The evolution of land plants from pond scum changed the face of the planet, making continents greener and producing habitats that would be conducive to animal life.
Scientists have been trying to establish an approximate date for the birth of land plants for decades. However, they lacked evidence in the form of hard shells or backbones as plants leave behind little fossil records. Moreover, biologists always felt that even the oldest fossils of plants do not exactly represent their earliest timeline.
Now, a new paper published in the journal Proceedings of the National Academy of Sciences on Feb. 19 has shown that land plants originated a hundred million years before the 420 million years that scientists had previously estimated. The results indicate that land plants' ancestor existed in the middle of the Cambrian Period, which was similar to the earliest known land animals' age.
The Importance Of Land Plants
Plants have played a crucial role in regulating the climate and atmosphere of the Earth for more than millions of years. They have a major contribution to continental rocks' chemical weathering, which is a primary step in the carbon cycle.
“[This] study has important global implications, because we know early plants cooled the climate and increased the oxygen level in the Earth’s atmosphere,” said Tim Lenton, a University of Exeter scientist who is not involved with the study.
Establishing The Timeline Of Land Plants
The research team associated with the study used the method of molecular clock to determine when land plants originated. The process put together proof on the genetic difference between fossil constraints and living species on their common ancestors' age. Subsequently, they established an evolutionary timeline that could look through the blanks in the fossil records.
"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," study co-lead author Dr. Jennifer Morris said.
Morris also added that earlier efforts to model such atmospheric changes have accepted the record of plant fossil at face value. The new research has shown that earlier established fossil ages underestimated land plants' origin, and therefore, those models must be updated.