Brazilian researchers have reconstructed the tree of life from the evolutionary history of amoebas and other organisms, revealing a surprisingly diverse ecosystem during the Neoproterozoic era.
Summary: New research suggests that Earth’s biodiversity 800 million years ago was more complex than classical theory indicates, with multiple lineages of eukaryotes surviving through major climate events.
Estimated reading time: 5 minutes
A study published in the Proceedings of the National Academy of Sciences (PNAS) challenges our understanding of Earth’s biodiversity 800 million years ago. Brazilian researchers have discovered that life on our planet during the Neoproterozoic era was far more diverse than previously believed, with multiple lineages of eukaryotes thriving despite severe climate changes.
The research team, led by Professor Daniel Lahr from the University of São Paulo’s Institute of Biosciences, focused on reconstructing the evolutionary history of amoebozoans. Their findings suggest that many organisms, including ancestors of plants, algae, fungi, and animals, were already well-established during this period and survived through the extreme glaciations of the Cryogenian period.
Rewriting the Neoproterozoic Paradigm
The classical view of the Neoproterozoic era (1000-541 million years ago) suggested a planet with minimal life forms, primarily consisting of a few species of bacteria and protists. However, recent fossil discoveries and this new study paint a different picture.
“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,” explains Lahr. “In the last 15 years, however, fossils of unicellular, eukaryotic and heterotrophic organisms have been identified at various different locations around the world. These fossils date from about 800 mya [and are termed Tonian].”
The study’s reconstruction of the tree of life pushes back the timeline for mass diversification of life on Earth by approximately 260 million years, well before the famous Cambrian explosion. This new perspective suggests a more gradual and resilient evolution of life forms, capable of adapting to extreme environmental changes.
Innovative Techniques Unveil Ancient Life
The researchers employed cutting-edge techniques to rebuild the phylogenetic tree, starting with the genus Thecamoeba. One of the key innovations was the use of single-cell transcriptomics, which allows for the sequencing of an entire transcriptome from a single cell or unicellular organism.
“Before this technique was invented, it was possible to obtain only transcriptomes of single-cell organisms living in culture, meaning less than 1% of the full diversity of microorganisms,” Lahr notes. This breakthrough enabled the team to structure the phylogeny of Thecamoebae as a whole, providing crucial calibration points for the broader tree of life.
Implications for Understanding Earth’s History
The study’s findings have significant implications for our understanding of Earth’s climate history and the resilience of life. The research shows that eukaryotes displayed greater adaptability than expected, surviving through major climate events such as the Cryogenian glaciations.
“The eukaryotes remained highly diverse despite all the climate changes that occurred during the Neoproterozoic, displaying greater adaptability than expected. This is important because our reconstitution of the phylogenetic tree also serves as a basis for paleoclimate reconstruction research,” Lahr explains.
An interesting observation from the study is the shift in habitat preference for Arcellinid amoebae. These organisms, which now exclusively inhabit freshwater environments, were found to have lived in saltwater during the Neoproterozoic. This dramatic change in habitat preference across all lineages further underscores the remarkable adaptability of these ancient organisms.
Addressing Potential Concerns
Some scientists may question the reliability of reconstructing evolutionary histories over such vast timescales. However, the researchers’ use of innovative techniques like single-cell transcriptomics and their careful calibration with fossil records provide a robust foundation for their conclusions.
Another potential concern is how these findings might impact our understanding of major evolutionary events like the Cambrian explosion. Rather than diminishing the importance of such events, this research suggests a more nuanced view of evolution, with periods of gradual diversification punctuated by rapid expansions of biodiversity.
As we continue to uncover the secrets of Earth’s ancient past, studies like this one remind us that the history of life on our planet is far more complex and resilient than we once believed. The diversity of life 800 million years ago not only survived extreme climate changes but also laid the foundation for the rich tapestry of life we see today.
Quiz: Test Your Knowledge on Ancient Earth Biodiversity
- According to the study, when did the mass diversification of life on Earth begin? a) 541 million years ago b) 635 million years ago c) 800 million years ago d) 1.5 billion years ago
- What innovative technique did researchers use to reconstruct the evolutionary history of ancient organisms? a) Carbon dating b) Single-cell transcriptomics c) DNA hybridization d) Electron microscopy
- What surprising discovery was made about Arcellinid amoebae? a) They went extinct during the Cryogenian period b) They evolved from multicellular organisms c) They lived in saltwater during the Neoproterozoic d) They were the first eukaryotes to develop a nucleus
Answers:
- c) 800 million years ago
- b) Single-cell transcriptomics
- c) They lived in saltwater during the Neoproterozoic
Further Reading
- Full study in Proceedings of the National Academy of Sciences (PNAS)
- University of São Paulo’s Institute of Biosciences
- More about the Neoproterozoic Era
Glossary of Terms
- Neoproterozoic Era: A geological era lasting from about 1000 to 541 million years ago, characterized by significant climate changes and biological evolution.
- Eukaryotes: Organisms whose cells have a nucleus enclosed within a nuclear envelope.
- Phylogenetic Tree: A branching diagram showing the evolutionary relationships among various biological species based on similarities and differences in their physical or genetic characteristics.
- Transcriptomics: The study of the complete set of RNA transcripts produced by the genome under specific circumstances or in a specific cell.
- Cryogenian Period: A geologic period within the Neoproterozoic Era, lasting from 720 to 635 million years ago, characterized by severe glaciations.
- Thecamoebians: A group of testate (shelled) amoebae that are important in reconstructing ancient ecosystems.
Enjoy this story? Get our newsletter! https://scienceblog.substack.com/
