(CN) – In a finding that guarantees a rewrite for science textbooks everywhere, scientists have discovered that contrary to long-standing theory, multi-celled animals developed from something similar to stem cells.
For a century, it's been believed that multicelled animals evolved from a single-celled ancestor resembling a modern sponge cell known as a choanocyte.
But the team from the University of Queensland mapped individual cells, sequencing all of the genes expressed, allowing the researchers to compare similar types of cells over time. Using new technology, the team was able to trace the evolutionary history of individual cell types by searching for the “signatures” of each type.
Professor Bernie Degnan said the results contradicted years of tradition.
“We've found that the first multicellular animals probably weren't like the modern-day sponge cells, but were more like a collection of convertible cells,” Degnan said in a statement.
“The great-great-great-grandmother of all cells in the animal kingdom, so to speak, was probably quite similar to a stem cell. This is somewhat intuitive as, compared to plants and fungi, animals have many more cell types, used in very different ways – from neurons to muscles – and cell flexibility has been critical to animal evolution from the start.”
Study co-author Sandie Degnan added, “Biologists for decades believed the existing theory was a no-brainer, as sponge choanocytes look so much like single-celled choanoflagellates – the organism considered to be the closest living relatives of the animals,” she said. “But their transcriptome signatures simply don't match, meaning that these aren't the core building blocks of animal life that we originally thought they were.”
Bernie Degnan acknowledged their study takes “a core theory of evolutionary biology and turning it on its head. Now we have an opportunity to re-imagine the steps that gave rise to the first animals, the underlying rules that turned single cells into multicellular animal life.”
Researchers hope the revelation will further science’s understanding of stem cells and the nature of cancer cells and their development.
The team published their findings Wednesday in the journal Nature.
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