Summary: By Richard I. Gibson Here is the podcast: Grypania spiralisWhen I wrote the book back in 1994, the oldest eukaryote organisms – single-celled creatures with a distinct nucleus – were thought to be algae from the Beck Spring Dolomite of Eastern California. They are about 1.3 billion years old, and some of those algal cells were large enough to be megascopic - seen with the naked eye. In 2004 S. Sarangi and colleagues at the National Geophysical research Institute in Hyderabad India reported an age of 1.6 billion years for the megascopic alga Grypania spiralis. Some dates from Michigan have suggested that Grypania is as old as 2.1 billion years. Understanding the timing and worldwide extent of things like megascopic algae has implications for understanding the evolution of the atmosphere and its oxygen content. Scientists who work on these problems try to correlate the timing of global algal blooms with evidence of oxidation in banded iron formations to get at the timing of changes in atmospheric oxygen. Photo by Xvazquez, via Wikipedia under GNU free documentation license.
