With the publication of a new study in the leading scientific journal Nature, a group of researchers from the University of Queensland may have overturned the way scientists think of the evolution of animals on Earth.
Thanks to advanced technology, the group was able to make an intuitive, yet unexpected discovery: “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,” said co-author on the study Professor Bernie Degnan.
The reason why the discovery was unexpected is because it contradicts the widely-accepted view that animals have evolved from a single-celled ancestor which resembles a modern-day sponge cell known as a choanocyte.
Unexpected or not, however, a pluripotent ancestor makes both intuitive and theoretical sense because, unlike plants and fungi, animals have a much greater variety of cell types, which seems to require a non-trivial degree of developmental flexibility.
“With multicellularity came incredible complexity, creating the animal, plant, fungi and algae kingdoms we see today. These large organisms differ from the other more-than-99-per-cent of biodiversity that can only be seen under a microscope,” explained Degnan.
The discovery was made by sequencing the genes expressed within individual cells, thereby allowing the researchers to compare similar types of cells over time.
A great part of the appeal of the current view on animal evolution comes down to the remarkable similarity between choanocytes and choanoflagellates (an organism considered to be the closest living relative to animals), yet the group found their transcriptome signatures to be largely unmatched.
“This technology has been used only for the last few years, but it’s helped us finally address an age-old question, discovering something completely contrary to what anyone had ever proposed. We’re taking a core theory of evolutionary biology and turning it on its head,” said co-author Associate Professor Sandie Degnan.
In addition to allowing theoreticians and biologists to re-imagine the sequence of events that must’ve taken place before animals appeared on the evolutionary scene, the new discovery could also help us gain a deeper understanding of our own stem cells and the mechanisms behind chronic diseases like cancer.