text:  I've always thought Luca was such a great name, but do we know what this thing was yet? No, not really. But the work here is trying to estimate when it was, right? So you track the rate of mutations backwards. How long would it have taken to pile up all the billions of mutations that led to all the different species of life? And they come up with an answer of 4.2 billion years ago, which is about 400 million years after the formation of Earth, which is like...