Complex life on Earth, similar to plants and animals, is roughly 800 million years older than previously thought, according to a genetic analysis of modern-day organisms by the Massachusetts Institute of Technology (MIT).
MIT’s genetic analysis found that eukaryotes were on Earth as early as 2.33 billion years ago, almost as soon as oxygen became a permanent part of the atmosphere. Eukaryotes are organisms whose cells contain a nucleus and other organelles enclosed within membranes. All modern animals, plants and fungus are eukaryotes.
MIT scientists examined the “molecular clocks” of modern life and worked backward to trace the evolution of gene sequences across hundreds of modern-day species. The team focused on DNA for the creation of sterol, which is a type of molecule that influences how their eukaryotes’ cells behave.
“The age of eukaryotes has been argued for decades, and there are widely differing opinions,” Dr. Roger Summons, a professor of geobiology in MIT, said in a press statement. “We’re putting out this piece of evidence that we think is significant, that says we believe that sterol was being made at least 2.3 billion years ago, and that the earliest eukaryotes were here at least that long.”
Since random mutations in DNA occur at relatively constant rates, the MIT researchers were able to track time by these changes. Using techniques comparable to to modern ancestry tracking in humans, researchers were able to look backward in time to the earliest point at which those sequences existed in eukaryotes.
“People have known for many years that they can work out ancestries from DNA, including the ancestry of humanity,” Summons said. “We know a lot about the connections between Neanderthals, Denisovans, and other early groups of humans from pieces of DNA in bone. But that’s projecting back a couple million years. We’re projecting back 2.3 billion years. So we’re showing modern DNA can be used to understand key events in the history of life, billions of years ago.”
This research was financially supported by the private Simons Foundation and Agouron Institute as well as government funding from the National Science Foundation.
The animals and plants in question were not as complex as modern ones. Scientists still believe that the first very complex multi-cellular animals did not appear until about 600 million years ago and were not diversified until roughly 542 million years ago in the Cambrian “explosion.”
Earlier this month scientists announced the discovery of a 3.7-billion-year-old fossil fossil which indicated that the origin of simple single cell life likely started up to 4.5 billion years ago. Before this discovery, the oldest confirmed life on Earth was dated to 3.4 billion years ago, leading scientists to speculate that life probably started around 3.7 billion years ago.
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