Millions of years ago, a random genetic accident may have enabled all of modern multicellular life to evolve.
A single change was all that was needed to make the jump from single-celled life, like bacteria, to all multicellular life, including humans, scientists reported Jan. 7 in a study published in the journal eLIFE.
The findings not only explain a critical chapter of evolution, they also offer tantalising clues to what goes awry when cancer cells stop functioning as team players and go back to acting like single-celled organisms, the researchers say.
A single genetic tweak
DNA encodes proteins, the molecules that perform all of the vital jobs in living cells. Mutations are random changes that occur in DNA when a cell divides. While most mutations are fatal to the organism, occasionally they can actually introduce a new piece of cellular machinery that can do something amazing.
In this case, a mutation allowed single-celled creatures to form a complex with each other, which gave rise to multicellular life.
“Our work suggests that new protein functions can evolve with a very small number of mutations,” University of Oregon biochemist Ken Prehoda, who led the study, said in a statement. “In this case, only one was required.”
The origin of all animals
To discover this mutation, Prehoda and his colleagues studied a group of microscopic sponge-like creatures called choanoflagellates, which are the closest living single-celled relatives of animals. These tiny, sea-dwelling creatures have a tail, or flagellum, for swimming around, and can live on their own as well as in large colonies.
The researchers used a technique called ancestral protein reconstruction to go “back in time” to trace the genetic changes that led these single-celled creatures to evolve a protein that is critical for multicellular life.
They found that a mutation in the gene that encoded the animal’s tail allowed it to align itself with other cells as part of a colony. This appears to have been the crucial step that allowed single-celled organisms to evolve into multicellular species. A version of this mutation can now be found in all animals, according to the researchers.
This genetic blip “was not solely responsible for the leap out of single-cellular life,” The Washington Post notes, but without it, we (and all our multi-celled cousins) might not be around.
And the findings don’t just satisfy scientists’ curiosity over how we evolved. Cancer is a disease where cells basically “forget” that they’re part of a multicellular organism, Prehoda told The Post, so understanding what makes this happen could lead to better treatments, he said.
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