Following on from Thomas’s point above, I thought most of Utah was covered in glaciers during the last ice age, and the remainder covered by Lake Bonneville (whose remnant is the Salt Lake that gives its name to Salt Lake City). But evidently there must have been a few patches of vegetation here and there, including this oversized bush.

See what i mean? to say that MCO are different from Unicellulars begs the question ‘how’? The distinction implied in your post seems to be sexual vs. asexual reproduction. What about lateral gene transfer then? does that break the magic line of how much genetic difference constitutes a ‘new’ organism? diploidy? single point mutation? it’s all arbitrary. we can put labels on it for convenience’s sake; but really – we are all really, really, really old.

While it is fine that for people who don’t work in the field, Dawkins is the first word on
evolution, he shouldn’t be the last word. Note that his “selfish gene” idea is NOT
universally accepted among researchers in the field, at least not with the enthusiasm
he has for it.

See, for example, Stephen Jay Gould’s magnum opus THE STRUCTURE OF EVOLUTIONARY
THEORY. I’m sure he has also discussed this at a less technical level in some of his
natural history essays, but I don’t have the titles offhand.

Note: Gould’s side of the story might, of course, be biased in Gould’s favour, but it is
certainly not more biased than Dawkins’s version. Gould explicitly addresses Dawkins’s
view; I don’t know if Dawkins has ever responded and addressed Gould’s view.

I am not an expert, but I think that, from a gene’s-eye-view, the benefit of sexual reproduction is still a bit of a mystery. In Dawkins’s Selfish Gene book, he argues that selection takes place at the level of the gene. A gene only cares about what happens to the species up to the point that it benefits itself; but in sexual reproduction, a gene only has 50% chance of being passed on.

Why are we not all asexual and immortal?

It’s been hypothesized (I don’t know how much evidence is yet available) that sexual reproduction in plants and animals arose as a result of competition against parasites. Parasites, with such dramatically faster reproductive cycles, can easily out-evolve their hosts. If the next generation has the same genetic makeup as the previous, then the parasites just continue to evolve while the hosts’ immune system stays nearly the same, and the hosts die.

If, by contrast, the hosts engage in recombination, then the genetic makeup of their descendants is different, and the parasites are forced to evolve all over again to survive in the presence of their new host. This gives sexually-produced young an advantage.

Mutation is ultimately a concern, but not on the kind of time scales we’re usually talking about with trees. And even then, harmful mutations are unlikely to get preserved in the long term, as natural selection works its inexorable logic on the cells of each part of the organism.

probably doesn’t rival in age, but certainly contends for the biomass record