Ediacaran biota
Fossils in Canada reveal the true origins of sexual reproduction in animals.
A discovery in the remote mountains of northwestern Canada is forcing paleontologists to revise the chronology of the origins of sexual reproduction in animals.
Fossils found in the Mackenzie Mountains, in the Northwest Territories, indicate that organisms of the genus Funisia already reproduced sexually about 567 million years ago — between five and ten million years earlier than previously thought.
Funisia it was an animal with a soft body, motionless, fixed to the seabed, with an appearance that vaguely resembled a coral. Although not very impressive at first glance, the organism is considered the oldest known example of sexual reproduction between animals, highlights the . As it did not move, reproduction would not involve direct contact between individuals: The animals would release sperm and eggs into the water column, where the reproductive cells would meet.
The discovery was made in a fossil bed that preserves more than a hundred multicellular animals belonging to the so-called ediacaran biotaa set of life forms that predates the Cambrian explosion of animal diversity.
Until now, scientists divided the fossil record of this biota into three major phases: Avalon, between 575 and 559 million years ago; White Sea, between 559 and 550 million years old; and Nama, between 550 and 538 million years ago. The new fossils belong to the White Sea phase, but will be significantly older than previously known specimens from this assemblage.
Sexual reproduction represented a decisive turning point in the history of life. For billions of years, living beings were dominated by microorganisms that reproduced asexually, creating copies of themselves.. By combining genetic material from two individuals, sex dramatically increased genetic diversity and accelerated evolution, paving the way for the variety of animals that would later occupy the oceans, land, and air.
The new site has great potential for understanding the transition in which life became larger, more complex and unequivocally animal, argues the study’s lead author, Scott Evans.
Another important aspect of this study is the environment where the fossils were found. The site appears to correspond to deeper waters than those previously associated with the White Sea assemblage. For the researchers of the study in Science Advances, this reinforces the idea that some of the first evolutionary innovations of animals, including sexual reproduction, could have emerged in the deep ocean, an environment that is dark but relatively stable in temperature and oxygen.
