Untangling the Role of Environmental and Ecological Influences on the Proterozoic Rise of Complex Life

Fri 5 Apr 2019

Space Telescope Science Institute (STScI) Bahcall Auditorium 3700 San Martin Drive Baltimore, MD 21218


12:00 PM - 2:30 PM


Phoebe Cohen (Dept. of Geosciences, Williams College)

The origins of complex life lie in the Neoproterozoic Era, which began 1,000 million years ago. How, why, and when complex life, including multicellularity, evolved on Earth is a critical question in astrobiology because it is our only example of the phenomenon, and enables us to better understand the conditions under which complexity might evolve elsewhere. The two main driving factors in the evolution of complexity are changing ecosystems, and changing environments. Here, I will attempt to untangle the influences of these two critical factors on Neoproterozoic evolution. Predation, and how organisms respond to it, is an important ecological interaction across the tree of life. Much of our understanding of predation focuses on modern metazoa. However, predation is equally important in single-celled eukaryotes (commonly referred to as protists). In the fossil record, we see evidence of protists preying on other protists beginning in the Tonian Period (1000–720 Ma). In addition, the first evidence of eukaryotic biomineralization and the appearance of multiple unmineralized but recalcitrant forms are also seen in the Tonian and Cryogenian (720–635 Ma), potentially indirect evidence of predation. This fossil evidence, coupled with molecular clock analyses, is coincident with multiple metrics that show an increase in the diversity of eukaryotic clades and fossil assemblages. Predation, thus, may have played a critical role in the diversification of eukaryotes and the evolution of protistan armor in the Neoproterozoic Era. However, major environmental changes were also occurring in the Neoproterozoic coincident with this diversification including the changing redox state of the ocean, and two major global glaciation events known as Snowball Earths. I will discuss how these major environmental transitions as well as the rise of eukaryotic predation upon other eukaryotes (eukaryovory) may have played a role in evolutionary innovations including the origins of biomineralization and metazoans. 


Light lunch (provided) starts at 12pm; talk starts at 12:30pm.

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