Recent Research Outlines Two Billion Years of Biodiversity Evolution
Recent Research Outlines Two Billion Years of Biodiversity Evolution
A group of international scientists released an intricate examination of the planet's biological variety spanning over 2 billion years, utilizing a worldwide collection of fossil data.
The fossilized remains of creatures with resilient components, like bones and shells, present a clear picture of evolution and extinction occasions throughout the past 500 million years. However, life on Earth emerged much earlier, around 3 to 2 billion years ago. The initial life forms were primarily made up of microbial communities, seaweed, sponges, worm-like creatures, and jellyfish, leaving minimal markers for fossilization. Proterozoic fossils, dating from 2,500 to 539 million years ago, feature impressions of bodies in delicate sediments, stromatolites, trace fossils, chemical and isotopic residues.
This recent study, utilizing readily available fossil data, constructed a diversity curve covering 2 billion years, showing that around 600 million years ago, a sequence of super ice ages ignited a substantial period of expansion for life on Earth.
As highlighted by Virginia Tech geobiologist and co-author Shuhai Xiao, "This is the most comprehensive and up-to-date analysis of this time period to date. And more importantly, we’ve used a graphic correlation program that allowed us to achieve greater temporal resolution."
The research team focused on the historical records of ancient marine eukaryotes - organisms whose cells contain a nucleus. Eukaryotes were critical to the development of multicellular organisms, including animals, plants, and fungi.
The first eukaryotes appeared at least 1.8 billion years ago, gradually evolving to a stable level of diversity between 1,450 to 720 million years ago, a period infamously known among paleontologists as the "boring billion." Evolution seemed to progress at a slower pace, with species surviving for longer periods.
Between 720 million and 635 million years ago, the Earth underwent a series of extreme ice ages. Ice blanketed nearly the entire planet, leaving behind debris from glaciers at the equator. Once the ice melted, evolutionary development gathered momentum, and the Earth was no longer as dull. Complex and large organisms started appearing in the fossil record close to approximately 580 million years ago.
According to Xiao, "The ice ages played a significant role in shaping the evolutionary path in terms of diversity and dynamics. We observe a rapid turnover of eukaryotic species immediately following glaciation. That’s a major finding."
The precise mechanism behind how the ice ages triggered evolution remains unclear. One possible explanation proposes that ice sheets eroded the continents, leading glaciers to deposit nutrient-rich sediments in the oceans, fostering an environment suitable for complex life to develop.
This study, titled "Quantifying the global biodiversity of Proterozoic eukaryotes," was published in the journal Science and can be read in full here.
Additional information and interviews provided by Virginia Tech.
The study utilizing Proterozoic fossils revealed various types of evidence, including impressions of bodies, stromatolites, and trace fossils, contributing significantly to our understanding of early life on Earth.
The extensive examination of fossil data not only constructed a diversity curve covering 2 billion years but also identified the influence of extreme ice ages on the evolution of early eukaryotes.