As far as we know, they look so different. Mysterious creatures that lived in the ocean half a million years ago: headless, limbless things, seemingly alien to us in every way.
Except they weren’t, new research suggests. In fact, the Ediacaran biota, a collection of ancient oceanic life forms that lived on Earth between 570 and 539 million years ago, has shared a number of genetic similarities with modern metazoans (multicellular animals). ), including humans, according to scientists.
It’s not that the similarities border on the weird, or anything.
“None of them had a skeleton,” says paleobiologist Mary Droser of the University of California, Riverside.
“Many of them probably looked like three-dimensional bath mats at the bottom of the sea, round discs that stuck together.”
Droser has a specialty in investigating foreign organisms from Earth’s distant past.
A year ago, he led a study that identified an Ediacaran like this: Ikaria wariootia, a strange, slow bellows the size of a grain of rice, which may have been the earliest ancestor of all animals with bilaterally symmetrical bodies.
However, not all ediacs necessarily have such close ties to animals.
There are more than 40 recognized species of the period, including the most famous, the ovoid Dickinsonia, and another named after President Obama – and it’s not always easy to determine where their fossilized forms should settle in the tree of life.
“These animals are so strange and so different, it’s hard to assign them to modern categories of living organisms just by looking at them,” Droser says. “And it’s not that we can extract their DNA, we can’t do that.”
Without being able to analyze first-hand the genetic data of these creatures, researchers must conform by inferring what they can from the fossil traces left behind by these organisms. Fortunately, these old footprints can reveal a bit.
In a new study co-authored by Droser and led by first author and paleontologist Scott Evans of the Smithsonian National Museum of Natural History, the researchers examined four representatives of the Ediacaran biota: Dickinsonia, Ikaria, the slug Kimberella, and the hemispherical blob Tribrachidium.
Based on observations of fossils and what we can deduce about how these creatures may have moved their bodies, sustained themselves, and generally lived their lives on ancient seabeds, the researchers propose that the animals probably contained a rudimentary form of the nervous system and regulated by the same type of genetic regulatory elements that are still used by living animals today, including humans.
“This analysis shows that it is likely that the genetic pathways of multicellularity, axial polarity, musculature, and nervous system were present in some of these early animals,” the authors write.
“Together these traits help to better restrict the phylogenetic position of several key Ediacara taxa and inform our views on the evolution of early metazoans.”
Specifically, in the new study, the team describes a wide range of genes that may have influenced multicellularity, immunity, nerves, apoptosis (programmed cell death), the axial pattern that differentiates the sides of a body, such as the front or back and left or right)), and more.
While there is still much to learn about these truly ancient creatures, the biology that unites us for millions of years shows that they may not be as strange as they seem.
“The fact that we can say that these genes were operating on something that has been extinct for a billion years is fascinating to me,” Evans says.
The findings are reported in Proceedings of the Royal Society B.