From the little we know of them, they look so different. Mysterious creatures that lived in the ocean half a billion years ago – headless, helpless things that seem strange to us in every way.
Besides that it was not, 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 – would have shared a number of genetic similarities with modern metasons (multicellular animals), including humans, scientists say.
Not that the similarities border on the strange, 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 seabed, round disks sticking out.”
Droser has something of the 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, sluggish spot about as big as a grain of rice, which was possibly the earliest ancestor of all animals with bilateral symmetrical bodies.
Not all Ediacarans today necessarily have such close ties with animals.
There are more than 40 recognized species from the period – including the best known, the egg-shaped Dickinsoniaand another named after President Obama – and it’s not always easy to determine where their fossilized forms should sit in the tree of life.
“These animals are so strange and so different that it’s hard 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 – neither can we.”
Without being able to analyze the genetic data of these creatures firsthand, researchers must do so from the trace fossils left behind by these organisms. Fortunately, these old prints can reveal quite a bit.
In a new study, led by Droser and led by first 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 hemispheric spot Tribrachidium.
Based on observations of the fossils and what we can deduce about how these creatures move their bodies, sustain themselves and generally lived on the old seabed, the researchers suggest that the animals probably contain a rudimentary form of nervous system, support and is regulated by the same types of genetic regulatory elements that are still used today by living animals, including humans.
“This analysis shows that the genetic pathways for multicellular, axial polarity, muscling, and a nervous system were probably present in some of these early animals,” the authors write.
“Together, these traits help to better limit the phylogenetic position of several important Ediacara taxa and to inform our views on early metazo evolution.”
In the new study, the team specifically outlines a wide range of genes that have influenced multicellularity, immunity, nerves, apoptosis (programmed cell death), axial pattern (which distinguishes the sides of a body, such as front or back and left or right), and more.
Although much is still known about these true ancient creatures, the biology that has united us for millions of years shows that it may not be as strange as it seems.
“The fact that we can say that these genes work in something that has been extinct for half a billion years is fascinating to me,” Evans says.
The findings are presented in Proceedings of the Royal Society B.