 When we look at the world today, it is more or less dominated by large complex organisms. These are eukaryotes. We are eukaryotes. But when we look into the geologic past, for some three billion years or so, the only things living in the world, the world's environments, were little single cell bacteria. This really begs the question, when exactly did the world transition from something that was dominated by little single cell primitive organisms into the world that we know and love today, which is teeming with complex life? For over 10 years now, it's been thought that this transition occurred sometime during the cryogenian, and this cryo quite literally means the freezing period. So the cryogenian began and finished with really intense glaciations, but somewhere in the middle, the world went hot and tropical for a while, and it's in these sediments that we believe that there's perhaps the first evidence of this explosion of complex life. But there is a problem, and that is that the kind of fossils we geochemists are looking at are not these kind of hard body skeletons. It's certainly not a T-rex bone that's poking out of the ground. The only remains that we can look at in the geologic past for rocks that are this old are little molecular remains, these single cells, this individual molecules that are kind of indicative of past life. There's a problem in that these molecular fossils are made of hydrocarbons, which are exactly the same type of stuff that petroleum products, plastics, the oil from our hands are made of. So these extremely pervasive contaminants. And although we had a bit of a handle on just how pervasive these contaminants can be, 10 years ago when we were looking at the geologic record, it wasn't quite as well understood as just how pervasive these contaminants could be. So we went back and looked at rocks of a similar age, and we extracted the biomarkers and we applied modern, rigorous cleaning techniques. So we were able to really clean up the biomarker record. And when we did that, we found that eukaryotes took over sometime during the early idiotic and not the cryogenia, and so some 20 million years later. And this is really important because it completely changes our understanding of what actually drove life to complexity in the first place.