Diverse life forms from 800 million years ago redefine evolution

What if our Earth, about 800 million years ago, was home to an abundance of diverse lineages of life — far more than the conventional evolution theories suggested?

This is the conclusion of a group of dedicated Brazilian researchers who meticulously reconstructed the tree of life from amoebozoans, the ancestors of algae, fungi, plants, and animals.

Diverse life forms and evolution

Sometimes, you uncover a tale so unexpected, so contrary to what you’ve always believed that it reshuffles your perception of the world.

The researchers, in their engaging endeavor, focused on eukaryotes — organisms made of one or more cells in which the DNA is enclosed within a distinct nucleus.

This encompasses all life on Earth except bacteria and archaea. The cornerstone of their study was the intriguing insight that these eukaryotes emerged around 1.5 billion years ago, and established themselves during the Neoproterozoic oxygenation event (850-540 mya).

This was a point in time when the oxygen levels in the planet’s atmosphere and oceans spiked due to changes in Earth’s geochemistry.

Against all odds

Unraveling the story further, the researchers also shed light on the resilience of these organisms. These ancestors of plants, algae, fungi, and animals withstood not one but two glaciations of the Cryogenian period (790-635 mya).

This period, smack in the middle of the Neoproterozoic Era, was marked by the Earth’s chilling transformation into a ‘snowball’, with polar ice blanketing the entire planet for around a cool 100 million years.

Now, that’s survival on a whole new level!

Legacy of the Neoproterozoic Era

Daniel Lahr, the professor at the University of São Paulo’s Institute of Biosciences (IB-USP) and the last author of the study, gives us a quick reality check on the classical paradigm surrounding the Neoproterozoic Era.

“The classical paradigm for the Neoproterozoic was that there was practically no life on the planet apart from one or two species of bacteria and protists,” he explains.

However, the last 15 years witnessed the identification of fossils of unicellular, eukaryotic, and heterotrophic organisms, taking us back to about 800 mya.

The study effectively pivots the mass diversification of life on Earth back by a game-changing 260 million years, much before the Cambrian explosion.

Evolution and tree of life

Lahr goes on to explain how this research serves as a foundation for further paleoclimate reconstruction research.

He elaborates on the stark transformation of Arcellinid amoebae, which were originally marine but now inhabit freshwater bodies. The adaptive nature of these organisms is awe-inspiring to say the least!

The research hinged on the evolutionary history of amoebozoans, specifically Thecamoebae.

By reconstructing the phylogenetic tree (a record of the organism’s evolutionary history) of this genus, the researchers could then build up the tree of life from there.

Evolution and tree of life

The research sheds light on an evolutionary leap that defied expectations. These findings propose that the diverse array of life forms we see today stemmed from a rich pool of single-celled organisms, thriving even in the face of harsh climatic conditions.

This view challenges the traditional narrative of life’s history on Earth, which often suggests that significant diversity only emerged post-Cambrian explosion.

By tapping into the genetic and fossil records, these scientists offer a broader understanding of how primitive life navigated and adapted through ancient Earth’s climate upheavals, suggesting that the seeds of complexity were sown much earlier than previously thought.

Implications for modern science

The ramifications of this study reach far beyond understanding past life; they provide a crucial framework for modern scientific inquiry.

This elucidation of ancient climate resilience holds valuable lessons for contemporary climate science, particularly in terms of understanding and predicting how current ecosystems might adapt to ongoing environmental changes.

Moreover, reconceptualizing the timeline of evolutionary history invites further interdisciplinary research, combining paleontology, geology, and molecular biology to explore life’s profound adaptability.

Through this lens, the study serves as a testament to the complexity and tenacity of life, motivating a re-examination of other periods marked by climatic shifts and the potential for undiscovered diversity within them.

Big picture

In simple terms, this research is about connecting the dots — lots and lots of them. By drawing upon previous discoveries and using advanced techniques like single-cell transcriptomics, the researchers have unearthed a treasure of information about life 800 mya.

Under the aegis of the São Paulo Research Foundation (FAPESP), this research has opened new doors in our understanding of Earth’s history, specifically the Neoproterozoic Era.

“Our analysis of the data showed that a great diversity of lineages began to emerge in the period, one of which was animals and another fungi, possibly alongside plants,” Lahr concludes.

Such important research is proof of humanity’s insatiable quest for knowledge, our endless fascination with life, its origins and evolution.

The story of Earth’s past continues to be written, pieced together from fragments of data and fossils, a proof of the extraordinary journey of life. Who knows what we may unravel next?

The study is published in the journal Proceedings of the National Academy of Sciences.

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