By studying the genetic tree of life, scientists have determined that the first life on Earth may have lived underwater, where it would be shielded from harmful ultraviolet light from the sun.
The origin of life on Earth remains a mystery, but scientists are slowly putting together genetic puzzle pieces to learn more about how the first life on Earth lived, between 2.5 and 4 billion years ago. Now, scientists from the University of Wisconsin-Madison and the University of California, Riverside, have used machine learning to trace the evolutionary development of a protein-based molecule called rhodopsin back to some of the most ancient microbial life-forms to have existed on Earth. The results may also inform the search for life beyond Earth, the scientists argue.
"It's like taking the DNA of many grandchildren to reproduce the DNA of their grandparents," astrobiologist Edward Schwieterman of the University of California Riverside, a co-author on the new research, said in a statement(opens in new tab).
The researchers suspect that rhodopsin provided the battery power for early life, turning light from the sun into energy. On modern Earth, rhodopsin can absorb blue, green, yellow and orange light. (It is also tangentially related to the light-absorbing rods and cones that our eyes use to see the world.)
Schwieterman and his colleagues began by using machine learning to look for the genes that control rhodopsin in as wide a swathe of life on Earth as possible, then identifying those genes that had the longest lineages.
This analysis suggested that ancient rhodopsin absorbed just blue and green light. This reduced capability makes sense in a scenario in which early life may have originated in the ocean, where blue and green wavelengths of light penetrate deeper into a column of water than other optical wavelengths: Being able to absorb these wavelengths to derive energy would have been vitally important. READ MORE...
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