How the Earliest Animals Lived on Earth and How They Became Extinct

Scientists are learning a bit more about how the earliest animals on Earth developed and evolve. They've created new, three-dimensional reconstructions that could show why these early animals became extinct.

The new reconstructions are of a strange group of organisms known as rangeomorphs. They were uniquely suited to ocean conditions about 575 million years ago, but eventually wound up becoming extinct. Their bodies were made up of small branches, each with many smaller side branches, and formed a geometric shape known as a fractal. This can be seen in many familiar branching shapes such as fern leaves and even river networks.

"We know that rangeomorphs lived too deep in the ocean for them to get their energy through photosynthesis as plants do," said Jennifer Hoyal Cuthill, one of the researchers, in a news release. "It's more likely that they absorbed nutrients directly from the sea water through the surface of their body. It would be difficult in the modern world for such large animals to survive only on dissolved nutrients."

The researchers created computer reconstructions of rangeomorphs after examining fossils from several different sites. This allowed them to see how well-suited these creatures were to their environment.

The oceans during this time period consisted of a weak soup that was full of nutrients, such as organic carbon. It's likely that rangeomorphs took advantage of this "soup" in order to support themselves.

Yet about 541 million years ago, the conditions of the oceans changed. With the start of the Cambrian Explosion, a period of rapid evolution, the competition for nutrients increased dramatically. This caused the rangeomorphs to die off. Yet before they did, they were remarkably well-suited to their environment.

"These creatures were remarkably well-adapted to their environment, as the oceans at the time were high in nutrients and low in competition," said Cuthill. "Mathematically speaking, they filled their space in a nearly perfect way. As the Cambrian began, these Ediacaran specialists could no longer survive, and nothing quite like them has been seen again."

The findings reveal a bit more about these ancient creatures and show that while they were suited to certain conditions, a changing ocean quickly caused them to go extinct. This shows researchers a little bit more about the very first animals that evolved on our planet.

The findings are published in the journal Proceedings of the National Academy of Sciences.

Want to learn more? Check out the video below, courtesy of YouTube.