An international team led by Chinese paleontologists has made significant advances in understanding early life evolution by mapping out, for the first time, a high-resolution biodiversity curve spanning from 2 to 0.5 billion years ago.

This groundbreaking research shed light on the evolutionary journey of early life forms on our planet, which navigated through multiple cycles of flourishing and extinction, culminating in the emergence of a complex ecosystem characterized by the iconic Cambrian explosion when a wide variety of animals burst onto our planet.

Fossils can offer key insights into life's evolution. Before 500 million years ago, however, the emergence of eukaryotic life and their first fossil traces remain uncertain. Eukaryotes are organisms having cells, each with a distinct nucleus within which the genetic material is contained, including fungi, plants, and animals.

Also, how the early life as ancestors of today's organisms evolved into diverse ecosystems on Earth is still a puzzle. This journey from simple to complex life forms is central to understanding biological origins and the future.

The study published in the journal Science on Friday has elucidated the origins and early evolution of eukaryotic organisms and offered some insights into potential extraterrestrial life and habitable planets.

The team invested six years in developing the world's biggest paleobiology database, including over 13,000 fossil events from around the world, and integrated supercomputing and AI tech to build the first high-resolution biodiversity curve.

They found that global glaciation events played a first role in the macroevolution of early life. The evolutionary trajectory of eukaryotes was disrupted by two global glaciation events between 720 and 635 million years ago, according to the study.

After that, the biodiversity surged and fluctuated, with a significant radiation event that peaked at 580 million years ago, followed by the first major extinction in the history of eukaryotes.

Subsequently, complex macroscopic organisms, including animals, appeared but faced two major diversity declines between 551 and 539 million years ago, marking the earliest two mass extinctions in animal evolutionary history, according to the study.

The research has revealed that life's evolution from simple to complex in about 1.5 billion years is not a linear process but a pattern of alternating long-term stagnation and relatively rapid growth.

The results also highlighted the profound effects of sudden environmental shifts, such as temperature and oxygen level, on early complex life, offering crucial implications for studying alien life in harsh conditions and evaluating the future habitability of Earth, said Tang Qing from Nanjing University, the first author and one of the corresponding authors of the paper.

A peer-reviewer praised the work as "a long overdue paper to examine the fossil record of the Proterozoic," which will make for "a plethora of papers following [its] publication."

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