New York: Researchers from Philadelphia-based Temple University, including an Indian-origin scientist, have assembled the largest and most accurate tree of life calibrated to time, revealing that life has been expanding at a constant rate.
The "Time Tree of Life" is depicted in a new way - a cosmologically-inspired galaxy of life view - and contains more than 50,000 species in a tapestry spiralling out from the origin of life.
"The constant rate of diversification that we have found indicates that the ecological niches of life are not being filled up and saturated," said professor S Blair Hedges and Sudhir Kumar, members of the research team.
This is contrary to the popular alternative model which predicts a slowing down of diversification as niches fill up with species, he added.
For the massive effort, researchers painstakingly assembled data from 2,274 molecular studies, with 96 percent published in the last decade.
They built new computer algorithms and tools to synthesise this largest collection of evolutionary peer-reviewed species diversity timelines published to date to produce the "Time Tree of Life".
The study also challenges the conventional view of adaptation being the principal force driving species diversification, but rather, underscores the importance of random genetic events and geographic isolation in speciation, taking about two million years on average for a new species to emerge onto the scene.
"This finding shows that speciation is more clock-like than people have thought," Hedges noted.
Besides the new evolutionary insights gained in this study, the "Time Tree of Life" will provide opportunities for researchers to make other discoveries across disciplines and the effect of climate change on future species diversity.
"The ultimate goal is to chart the timescale of life - to discover when each species and all their ancestors originated, all the way back to the origin of life some four billion years ago," the team wrote.
The paper was published in the journal Molecular Biology and Evolution.