The most boring billion years on Earth has been identified: what events unfolded on the planet during that period.

On Earth, ancient species evolved more slowly and existed for longer periods, but the pace of evolution significantly accelerated after global glacial periods, according to SciTechDaily.

A new study has managed to trace the cycles of rise and fall of ancient life over millions of years.

It is known that fossilized skeletons and shells provide a vivid timeline of evolution and extinction over the past 500 million years. Now, new analysis from the Virginia Polytechnic Institute extends this timeline by nearly 2 billion years.

Thanks to this new research, the diagram now includes life forms from the Proterozoic Eon, 2.5 billion to 539 million years ago. Proterozoic life was generally smaller and softer—like marine sponges that did not develop a mineral skeleton—and initially left fewer traces for fossilization.

Geobiologist Shuhai Xiao from Virginia Tech and his colleagues published a high-precision analysis of global diversity of Proterozoic life based on fossil data.

Xiao and his team specifically studied the records of ancient marine eukaryotes—organisms whose cells contain a nucleus. Early eukaryotes later evolved into multicellular organisms, which are credited with marking the beginning of an entirely new era of life on Earth, including animals, plants, and fungi.

"We have compiled the most comprehensive and up-to-date analysis of this period to date," said Xiao, who was recently elected to the National Academy of Sciences.

The first eukaryotes arose no later than 1.8 billion years ago and gradually evolved to a stable level of diversity from about 1.4 billion to 720 million years ago. This period is known as the "boring billion," when the rates of species turnover were extraordinarily low.

Eukaryotic species during the "boring billion" evolved more slowly and existed longer than those that appeared later.

The "boring billion" on Earth ended with a global cataclysm when the planet literally turned into a "snowball." A series of temperature drops encased the planet in ice at least twice between 720 million and 635 million years ago. When the ice eventually melted, evolutionary activity resumed, making things far less boring.

"Glacial periods were a key factor that reshaped the evolutionary path in terms of diversity and dynamics. We see a rapid turnover of eukaryotic species immediately after glaciation. This is an important finding," summarized the study's author.

Recall that ancient Earth was a watery world, and scientists have figured out where the giant oceans went. Researchers believe that in the past, the planet was completely engulfed by the ocean.