The oldest green seaweed on record, the ancestor of all land plants, lived about 1 billion years ago, a new study finds.
Scientists have discovered the fossils of what may be the oldest green algae ever known. The newfound seaweed — called Proterocladus antiquus — lived about a billion years ago. And even though it was tiny, about 0.07 inches (2 millimeters) in length, the algae had a big role: It could produce oxygen through photosynthesis.
"Its discovery indicates that green plants we see today can be traced back to at least 1 billion years ago, and they started in the ocean before they expanded their territory to the land," study lead researcher Qing Tang, a postdoctoral fellow in the Department of Geosciences at Virginia Tech, told Live Science in an email.
Until now, researchers didn't have hard proof that green algae lived that long ago. Rather, computer models, including those based on molecular clocks, indicated that photosynthesizing plants arose between the Paleoproterozoic era (2.5 billion to 1.6 billion years ago) and the Cryogenian period (720 million to 635 million years ago).
Now that researchers have a fossil, they can confidently say that photosynthesizing plants, a group known as Viridiplantae, lived at least 1 billion years ago, and that they were multicellular, Tang said.
"Previously, the oldest widely accepted fossilized green algae was about 800 million years old," said Timothy Gibson, a postdoctoral fellow in the Department of Earth Sciences at Dartmouth College in New Hampshire and the Department of Geology and Geophysics at Yale University, who was not involved with the study. "This work confirms what many have expected based on the existing, though sparse fossil record, which is that green algae likely existed about a billion years ago."
Tang and his colleagues discovered the fossils near Dalian City in Liaoning province of northern China. They had heard there was "a thick pile of well-exposed sedimentary rocks" from the Nanfen Formation dating to about a billion years ago. So, Tang took some of these ancient rocks, mostly mudstone and shale, back to the lab at Virginia Tech.
Tang was "really excited" when he saw the algae fossil under the microscope. In all, he identified 1,028 specimens. "I showed it to my supervisor [Shuhai Xiao, a professor in the Department of Geosciences at Virginia Tech], and we immediately agreed that this was going to be a very interesting discovery," he said.
Just like modern-day algae, P. antiquus has differentiated, branched cells and root-like structures, Tang said. It likely played an important role in the ancient ecosystem by producing oxygen, he said. In addition, it likely provided food and shelter to other organisms.
"Most of the organisms (particularly cyanobacteria) in this period were either planktonic or lying on the seafloor," Tang said. P. antiquus also grew on the seafloor, indicating that it could have served as an ideal place for living, hiding, resting for other organisms, he said.
Life on Earth is dependent on photosynthesizing plants and algae for food, yet land plants did not evolve until about 450 million years ago, Tang said. "The new fossil suggests that green seaweeds were important players in the ocean long before their descendants, land plants, took control," he said.
These fossils came from an ancient ocean, but there is still a debate about where green algae originated. "Not everyone agrees with us; some scientists think that green plants started in rivers and lakes, and then conquered the ocean and land later," Xiao said in a statement.
Moreover, green algae isn't the oldest algae on record. "There is strong fossil evidence that red algae existed over a billion years ago, and we know the red and green algae diverged from a common ancestor," Gibson told Live Science in an email. "So, although this doesn't fundamentally change the way I'll think about the evolution of life, the discovery of this green algal fossil helps fill an important gap and strengthens an emerging timeline for the evolution of early, complex life."
The study was published online yesterday (Feb. 24) in the journal Nature Ecology and Evolution.
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Laura is the archaeology and Life's Little Mysteries editor at Live Science. She also reports on general science, including paleontology. Her work has appeared in The New York Times, Scholastic, Popular Science and Spectrum, a site on autism research. She has won multiple awards from the Society of Professional Journalists and the Washington Newspaper Publishers Association for her reporting at a weekly newspaper near Seattle. Laura holds a bachelor's degree in English literature and psychology from Washington University in St. Louis and a master's degree in science writing from NYU.
Please note that "algae" is a plural noun; the singular of "algae" is "alga". So "algae" takes a plural verb: "algae are" and "algae were", not "algae is" etc. Grammar matters, and accurate names matter, especially in science writing.Reply
If it matters, I am a Ph.D. biologist with a long University teaching and research career focused on evolution, ecology and behavior -- and long experience editing other people's journal articles, etc. <G>.
Interesting, but saw nothing about how they determined the age of the algae. Hopefully, we have not returned to the circular reasoning of "the rocks determine the age of the fossils, the fossils determine the age of the rocks". The assumptions, the assumptions ...admin said:A billion years ago, this green seaweed likely produced oxygen and provided shelter for other organisms.
The oldest green algae on record is 1 billion years old : Read more
I assume It says in the journal paper, If you care to pay a few bucks to read it:createdworld said:Interesting, but saw nothing about how they determined the age of the algae. Hopefully, we have not returned to the circular reasoning of "the rocks determine the age of the fossils, the fossils determine the age of the rocks". The assumptions, the assumptions ...
From the abstract: "This model, however, has not been rigorously tested with palaeontological data because of the scarcity of Proterozoic chlorophyte fossils." Also from the abstract: "described", "interpreted", "suggesting" and "nearly a billion years ago, much earlier than previously thought." Just saying.hellopunyhumans said:I assume It says in the journal paper, If you care to pay a few bucks to read it:
You can read it if you click the linkReply
"Although there are no reliable radiometric ages directly from the Nanfen Formation, the youngest population of detrital zircons from the underlying Diaoyutai Formation is dated at 1,056 ± 22 Ma (ref. 25), and a diabase sill emplaced in the overlying Qiaotou Formation gives a zircon secondary-ion mass spectrometry U-Pb age of 947.8 ± 7.4 Ma (ref. 26). Hence, the depositional age of the Nanfen Formation is constrained between about 1,056 and 947.8 Ma, consistent with numerous other radiometric ages from the Xihe, Wuxingshan and Jinxian groups (Extended Data Fig. 1; see also Age constraints in Supplementary Information). "createdworld said:From the abstract: "This model, however, has not been rigorously tested with palaeontological data because of the scarcity of Proterozoic chlorophyte fossils." Also from the abstract: "described", "interpreted", "suggesting" and "nearly a billion years ago, much earlier than previously thought." Just saying.
They only use that language because science never has 100% certainty. Sure, the rock are dating the fossils, but molecular analysis is dating the rocks.