From what little we know about them, they seem so different. Mysterious creatures that lived in the ocean half a billion years ago – things without heads, without limbs, that seem strange 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 – is said to have shared some genetic similarities with modern metazoans (multicellular animals), including humans, scientists say.
Not that the similarities border on the spooky or anything.
“None of them had heads or skeletons,” explains paleobiologist Mary Droser of the University of California, Riverside.
“Many of them probably looked like three-dimensional bath mats on the sea floor, round discs sticking up.”
Droser has something of a specialty in researching creepy organisms from Earth’s distant past.
A year ago, she led a study that identified one such Ediacaran: Ikaria wariootia, a strange, slow blob the size of a grain of rice, which was perhaps the earliest ancestor of all animals with bilaterally symmetrical bodies.
However, not all Ediacarans today necessarily have such a close relationship with animals.
There are over 40 recognized species from the period – including the most famous, the ovoid Dickinsonia, and another is named after President Obama – and it’s not always easy to determine where their petrified shapes should be in the tree of life.
“These animals are so strange and so different that it is difficult to assign them to modern categories of living organisms just by looking at them,” says Droser. “And it’s not like we can extract their DNA – we can’t.”
Without being able to analyze the genetic data of these creatures firsthand, researchers have to do by deducing what they can from the trace fossils left behind by these organisms. Fortunately, those old prints can reveal quite a bit.
In a new study, co-authored by Droser and led by lead author and paleontologist Scott Evans of the Smithsonian National Museum of Natural History, researchers looked at four representatives of the Ediacaran biota: Dickinsonia Ikaria, the snail-like Kimberella, and the semicircular blob Tribrachidium
Based on observations from the fossils and what we can infer about how these creatures moved their bodies, sustained themselves, and generally lived their lives on the ancient seafloor, the researchers suggest that the animals are most likely a rudimentary form. of the nervous system, supported and regulated by the same types of genetic regulatory elements that are still used by living animals, including humans.
“This analysis shows that the genetic pathways for multicellularity, axial polarity, muscular and nervous systems were likely to be present in some of these early animals,” the authors write.
“Together, these properties help to better limit the phylogenetic position of several important Ediacara taxa and inform our views on early metazoic evolution.”
Specifically in the new study, the team outlines a wide variety of genes that may have influenced multicellularity, immunity, nerves, apoptosis (programmed cell death), axial patterns (which differentiate the sides of a body, such as 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 worked in something that’s been extinct for half a billion years is fascinating to me,” says Evans.
The findings are reported in Proceedings of the Royal Society B