Ancient species may have evolved slower and lasted longer, but the pace of evolution accelerated after global ice ages, according to a new Virginia Tech analysis. The study, published in the journal Science, maps the rise and fall of ancient life many tim

If all the world's a stage and all the species merely players, then their exits and entrances can be found in the rock record.

Fossilized skeletons and shells clearly show how evolution and extinction unfolded over the past half a billion years, but a new Virginia Tech analysis extends the chart of life to nearly 2 billion years ago.

The chart shows the relative ups and downs in species counts, telling scientists about the origin, diversification, and extinction of ancient life.

With this new study, the chart of life now includes life forms from the Proterozoic Eon, 2,500 million to 539 million years ago. Proterozoic life was generally smaller and squishier -- like sea sponges that didn't develop mineral skeletons -- and left fewer traces to fossilize in the first place.

Virginia Tech geobiologist Shuhai Xiao and collaborators published a high-resolution analysis of the global diversity of Proterozoic life based on a global compilation of fossil data, which was released Dec. 20 in the journal Science.

Xiao and his team looked specifically at records of ancient marine eukaryotes -- organisms whose cells contain a nucleus. Early eukaryotes later evolved into the multicellular organisms credited for ushering in a whole new era for life on Earth, including animals, plants, and fungi.

"This is the most comprehensive and up-to-date analysis of this period to date," said Xiao who recently was inducted into the National Academy of Sciences. "And more importantly, we've used a graphic correlation program that allowed us to achieve greater temporal resolution."

The choreography of species offers critical insights into the parallel paths of the evolution of life and Earth.

Observed patterns and insights suggested by the analysis:

"The ice ages were a major factor that reset the evolutionary path in terms of diversity and dynamics," Xiao said. "We see rapid turnover of eukaryotic species immediately after glaciation. That's a major finding."

The patterns, Xiao said, raise a lot of interesting questions, including:

Future scientists can use the quantified pattern to answer these questions and better understand the complex interplay of life on Earth and the Earth itself.

Study collaborators include: