I also enjoyed Lane’s book when I first read it several years ago. One thing that I’ve wondered about since then was whether evolution was responsible for the melding of two primitive life-forms, yielding our current cell-plus-mitochonria Eukaryotic world.
Here’s what I mean: imagine bacteria species A floating around, engulfing other microbes as food. Archaea species X is one of those unhappy bits of floating prey. Due to the random mutations that enable evolution to occur, one member of species X develops a slightly more resistant membrane. As this makes it more difficult for bacteria A to eat it compared to its peers, X-type archaea begin to dominate the population.
Eventually, after eating all the old-type archaea, bacteria A are forced to feed on species X (I’m assuming some kind of closed environment like a pond, wherein the overall balance of species is altered only by purely internal mechanisms). But because species X has this somewhat more resistant membrane, once it’s engulfed it stays in situ rather than being digested into its component molecules. And now, the Great Energy Sharing Game can accidentally commence.