Land plants and fungi may have arisen far earlier than previously thought, according to a study published today in the journal Science. The gene-based research suggests that the emergence of these organisms may have led to major climate and animal evolution events.

The Pennsylvania State University research team, led by evolutionary biologist Blair Hedges, based their findings on the so-called molecular clock. Genes known to accumulate mutations at a constant rate, much like a ticking clock, can be used to determine when a species originated. To figure out when land plants and fungi originated, the team analyzed 119 such molecular clock genes common to living species of animals, plants and fungi. Their results proved startling. In contrast to fossil-based studies that place the appearance of land plants and fungi at around 480 million years ago, the genetic findings indicate that land plants and fungi evolved approximately 700 million and 1,300 million years ago, respectively.

The early presence of plants and fungi on land would have reduced the amount of carbon dioxide in the atmosphere, producing a cooling effect, the authors note. At the same time, the plants boosted atmospheric oxygen levels, thus paving the way for the evolution of complex animals.