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How science discovered the first “Brazilians” with the help of rocks |  Land of people

How science discovered the first “Brazilians” with the help of rocks | Land of people

Stromatolite rocks in a salt lake, Rio de Janeiro – Photo: J Honório Freire / Wikipedia

Can you imagine what the planet looked like about 20 thousand years ago? Among rocks and other inorganic materials, Brazil had some organisms that managed to maintain their existence to this day. Find out who they are in this week's Natural History, a column written by Terra da Gente biologist Luciano Lima.

To this day, many students learn at school that Brazil was “discovered” by Europeans in April 1500, a word that implies there were no other humans on Brazilian soil when Pedro Álvares Cabral and his fleet arrived here. This is clearly an error, since the Portuguese themselves, in the letter Peru Vaz de Caminha, reported the presence of indigenous people in Brazil.

Going back a little further in time, Luzia, the oldest human fossil in Brazil and South America, was found very close to what is now Belo Horizonte, and is estimated to be between 12.5 and 13 thousand years before the present.

Other archaeological evidence as well as genetic evidence suggests A much older occupation of Brazil, which could be as old as or even exceed 20 thousand years. In other words, the fact that people already inhabited our lands long before Raul Seixas, the author of the song “I Was Born Ten Thousand Years Ago,” is indisputable.

“Natural Stories” is the weekly column written by biologist Luciano Lima for Terra da Gente – Photo: Arte/TG

Jokes aside, it is no coincidence that historians increasingly use the word “conquest,” not “discovery,” to refer to the arrival of Europeans in America. But if we leave anthropocentrism aside, and consider living organisms as a whole, Have you ever stopped to think about who the first “Brazilians” were?

Although the Earth formed about 4.5 billion years ago, the oldest rocks known so far in Brazilian lands are “younger,” at 3.6 billion years old.

It was described in 2022, and is located in Chapada Diamantina, Bahia, in the so-called São Francisco craton. Cratons are large regions that differ from most of the Earth's crust, in that the crust is thicker and therefore has Great mechanical strength and geological stability. They are pieces of the earth's crust that have survived and withstood time, and are testimonies of distant eras.

In addition to the oldest rocks on the planet, as expected, they are also… The first signs of life on Earth were found in cratons. Some evidence indicates the existence of life in Greenland rocks that are about 3.8 billion years old, but these and other discoveries are subject to a certain degree of interpretation and are often questioned.

The oldest known fossils, without much controversy, are about 3.4 billion years old and were found in the Pilbara Craton, located in Western Australia.

In other words, the oldest rocks found in Brazil are practically contemporary with the first strongest evidence of life on Earth. But what kind of life would that be? The answer is short, but practically speaking, it's tongue-in-cheek: Stromatolite.

Modern stromatolite at Sharkbay, Australia – Photo: Paul Harrison / Wikipedia

“Buildings” made by microorganisms

Stromatolites can fossilize in various ways and preserve not only the structure formed by cyanobacteria, but also the cyanobacteria themselves.

Although it is about a billion years younger than the stromatolite fossil found in the Pilbara Craton in Australia, The oldest known fossils in Brazil are also stromatolites. They are 2.4 billion years old and fossilized in the rocks of the Iron Square region of Minas Gerais, and are the oldest known fossils in South America.

Since we know that stromatolites only develop in very shallow waters, where cyanobacteria need light to perform photosynthesis, we can admit that stromatolites inhabit areas very close to Earth and not at the bottom of some primitive ocean.

Thus, Minas Gerais stromatolites are the oldest evidence of life in a piece of the Earth's crust which, along with other pieces of crust, billions of years in the future, would be called “Brazil” by a species of primate.

Stromatolites from Lake Thetis, Western Australia – Photography: Ruth Ellison

It is certain that the most ancient creatures that were not fossilized, or that were fossilized but not yet discovered, inhabited an ancestral part of the present-day Brazilian territory. But given what we know about the evolution of life on Earth, there was nothing very different about stromatolites 2.4 billion years ago, that is, 2.4 billion years ago. It is very likely that some cyanobacteria or other stromatolite-building microorganism was the first “Brazilian”.

The marble that makes up the floors of some of São Paulo's famous shopping malls, such as Shopping Eldorado and Shopping Ibirapuera, originates from a quarry near Ouro Preto, and walking through these malls it is possible to see very clearly the traces of flooring on the ground. Stromatolites are more than 2 billion years old!

But if you are not satisfied with fossils and want to see stromatolites in person and in color, you can visit Lagoa Salgada, located in the municipality of Campos dos Goytacazes, north of Rio de Janeiro. The hypersaline lake is one of the few places on the planet where “living” stromatolites can still be found. I was there and I admit I cried when I looked at what to many people looked like “weird rocks” on the banks of the lake.

Maybe I'm the odd one out, but it's exciting to think that organisms practically identical to the first organisms that existed in Brazil billions of years ago are still among us. The country of biodiversity is the country of birds, butterflies, mammals, beetles and fish, but above all, it is also the country of its cyanobacteria and stromatolites.

*Luciano Lima is an ornithologist and part of the Terra da Gente team

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