> It's fascinating to me that the complexity of life always goes up. Outside extinction events, complex life generally seems to become more favourable over time

> It's fascinating to me that the complexity of life always goes up. Outside extinction events, complex life generally seems to become more favourable over time. It's interesting that (to my knowledge) we don't see an ecosystem lose complexity in its entirety unless it's dying. I think that's a biased take. Complex life may be better at exploiting a more table environment, but too much disruption can kill it. "Less complex" life seems able to adapt more quickly to more extreme changes (e.g. the much greater diversity of bacterial metabolism). Extinction events are inevitable, and environmental disruption will inevitably become more and more challenging until everything dies (though it may take a billion years), and during that time I think the trend will be for complexity to decrease. So ultimately, I think you're overgeneralizing one phase.