This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers may have uncovered the reason why some of Earth's earliest animals were commonly preserved as fossils—even though they were essentially fragile "bags of goo"—while later soft-bodied creatures have largely disappeared from the fossil record. The researchers, led by the University of Cambridge, say that the reason may lie in the evolution of microscopic organisms capable of breaking down collagen, a structural protein found in animal tissue.
The fossil record of animal life on Earth is highly incomplete. Hard body parts like shells, bones and teeth are far more likely to be preserved than soft body parts like muscles, organs and skin, so the majority of the fossils we have today are mineralized skeletons. However, fossils from the late Ediacaran Period, between 579 and 539 million years ago, are different.
Fossils from this time, which include the oldest known complex forms of animal life, are frequently preserved in extraordinary detail, even though none of these earliest animals had any hard body parts. In some sites, entire Ediacaran ecosystems are preserved, providing a rich window into early animal evolution. For decades, researchers have debated how such common preservation of soft tissues was possible.
Possibilities include unusual chemical conditions in the Ediacaran oceans, different tissue compositions or the influence of a layer of microbial slime that covered the entire seafloor. However, while these explanations work in some places, none of them work everywhere. The Cambridge-led researchers say the answer may be the evolution of microbes that produce collagen-eating enzymes known as collagenases.
Their results are reported in the journal Current Biology. Collagen provides strength and support to animal tissues throughout the body. Once an organism dies, collagenases can rapidly break these tissues down, reducing the chances that they will be preserved long enough to fossilize.
"If you think about a modern jellyfish, for example, if it washes up on a beach and is left to decay, it will decompose in a matter of days," said lead author Philip Vixseboxse, who completed the work while a Ph.D. candidate at Cambridge's Department of Earth Sciences. "It will never become a fossil, but similarly squishy animals from half a billion years ago did commonly get preserved." Collagen is in all animal tissue, but without any enzymes to break it down, it will persist, like modern plastic. "You need an enzyme to break down a biopolymer, or else it will sit around for ages until something comes along that can actually eat it," said Vixseboxse.
Extract — continue reading at the source.
