Question: If the last common ancestor of the bacterium had a flagellum, what do we really know about the evolution of the flagellum? Isn’t that a bit like finding a stone laptop in a Neanderthal cave? That said, it’s nice to see horizontal gene transfer getting proper recognition.
One senses that the reconstruction will be subject to considerable revision. It’s not entirely clear what “ancestry” means in a world of rampant horizontal gene transfer.