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Study challenges classic theories about Earth's past (30 notícias)

Publicado em 15 de agosto de 2024

Classical theories about Earth's past are well accepted in scientific circles, but they may not be completely correct.

A recently published study shows that living beings already existed on the planet 800 million years ago, much earlier than current thinking suggests.

The discovery was published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS) and shows that, long before Pangea, Earth already had an impressive diversity of eukaryotic beings.

Earth's past was diverse long before we imagined

The study revealed that several lineages of eukaryotic beings (living beings with cells with delimited nuclei) that emerged 1.5 billion years ago established themselves and diversified 800 million years ago. This period was marked by the oxygenation of the Neoproterozoic (deep oxygenation of the oceans).

Classical theories about Earth's past predicted that this diversification would only occur during the Cambrian revolution, 540 million years ago – 260 million years later than current research suggests. In other words, the diversity of life on the planet is much older than previously thought.

Daniel Lahr, a professor at the University of São Paulo's Institute of Biosciences and senior author of the article, explained this paradigm shift to Agência FAPESP:

The paradigm we had for the Neoproterozoic was that there was almost nothing on the planet, just one or two species of bacteria and protists. However, in the last 15 years, fossils of unicellular, eukaryotic and heterotrophic organisms (which do not produce their own food) have been identified in several different places on the planet. (…) All of this is part of our study, which reconstructed the tree of life and, through probabilistics, identified several well-established lineages of ancestors of amoebas, animals, fungi and plants 800 million years ago. This greatly changes our understanding of how the diversification of life on Earth occurred.

Daniel Lahr, professor at the Institute of Biosciences at the University of São Paulo and senior author of the article, in an interview with Agência FAPESP

Study revealed that primitive beings on Earth were adaptable

Not only more diverse, but adaptable. This was another discovery from the study of the beings that inhabited the Earth 800 million years ago.

The team found that the diversity of amoebas and ancestors of plants, algae, fungi and animals survived several critical periods in Earth's past, such as two glaciation events (790 million years ago and then 100 million years ago).

For Lahr, this shows a power of adaptation that is above what was expected for these beings. One of the adaptations was the Arcellinida amoebas. Millions of years ago, they lived in salt water, and now they all live in fresh water.

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How the study was done

To reach these conclusions, the study traced a family tree of the kinship relationships of the thecamebas (Arcellinida); From this, they were able to identify the past of plants, fungi, algae and animals, which preceded the current species by millions of years; The insights present in the article were a result of this mapping with the help of probabilistic mathematics, which allowed them to determine the morphology of the beings and compare them with other fossils; The technique used is called single-cell transcriptomics and allows the sequencing of the entire transcriptome of a single cell. This, in turn, allows scientists to go back in evolutionary lineages to understand the Earth's past.