Yeah, I certainly didn't intend for it to be a faith/atheism battle. I'm simply stating that so far, all I've seen has been that one perspective. I'm interested in the potential fallout others are predicting.

That's highly debatable. Also, obviously 'most' begs the question 'most by what?' if it's just by number, then that seems unlikely but possible. But most by weight, volume, or, more importantly, functionality - not really, that's definitely human cells.

Interestingly, you're right in that the "most of your cells are bacteria" point is a myth. I'm not a specialist, and fell for the pop-sci BS. Apparently the real ratio is closer to 1:1 ( https://www.nature.com/news/scientists-bust-myth-that-our-bo... ), if we can trust Nature's summary of several recent articles.

With regard to functionality, that's a very open question. We're constantly finding that features that didn't seem useful are not just functional but important. This trend can be seen at multiple levels, from gut flora to "junk DNA."

As for what fraction of our genome is either shared with other non-human organisms or originated with them, it's tough to find a straight answer on that, but rest assured it's far from zero. See https://www.cshl.edu/the-non-human-living-inside-of-you/ . That's been well-understood by everyone other than religious fundamentalists for some time now, and there are countless legitimate sources that can be cited.

I am no religious fundemantalist (I'm actually an atheist), and care very little for the notion of purity of humanity. The idea of 'human DNA' vs 'non-human DNA' seems suspect to me, as in some trivial sense, anything that is in the genome of a human being is by definition human DNA, and on the other hand, you can find large swaths of human DNA that are identical to most mammals, and probably a few that are common to virtually all eukaryotes. I also know that viruses can leave long-lasting changes to your DNA, that may even be heritable I think.

Still, related to the importance of bacteria, while I don't doubt that, as we learn more, we will discover that they have a bigger role than even dreamed 50 years ago, you still can't compare it to the basic roles of human organs. We have actually created microorganism-free mice and other organisms, and while they are not very healthy, they are fully functional (with bad digestion and big immune problems): https://en.m.wikipedia.org/wiki/Germ-free_animal

Why aren't you fond of transhumanism? At some point medicine and technology will advance so much that we can save and improve many lives by replacing bits of ourselves with superior artificial variants. Is that so bad?

I don't even care about the risks. It's about changing the rules so much that we don't know what game we're even playing. If you stop caring what's technically a human anymore, you have to reconsider the imperative to propagate the human race. Who are you propagating and why? What's the point of any of it anyway?

Granted I'm disinclined to propagate the human race anyway, so I guess I may actually be ahead of you.

I don't consider it being ahead to be disinclined to propagate the human race. I mean, if you're just advocating that for yourself that is one thing. But advocating that as a position in general is misanthropic and in my view not a tenable or healthy position.

In any case, if you don't care about the risks and are just concerned with the meaning about why we propagate and what the point of anything is, then I must point out that I'm not super interested in discussing this. I was more getting at why someone would oppose transhumanism, but this doesn't seem tone a meaningful critique of transhumanism as much as it is a sort of pessimism about why we do anything or we should propagate at all.

As with all the progress, along with the good things transhumanism will bring, it will bring a hefty bag of bad things. And if you entertain the thought for a while, those bad things can be really, really bad, on a number of different axis.

Right, but just because bad things have come from science and technology doesn't mean that we get rid of science and technology. It means we have to be more vigilant about doing good things with our tools.

You first.

More seriously, this is one of those situations where the short-term pluses are plain to see, but the long-term risks are vague. Why not employ the precautionary principle here?

Instead of simply alluding to long-term risks, can you be more specific about what exactly you're concerned about? What kind of precautions are you advocating? At some point medical technology will give us organs that are far superior to biological organs - should we not make these available to people?

It really depends what we're talking about here. Specific to your comments I can think of a couple things:

1) In terms of organ replacement, I agree it's a great opportunity -- but, we really won't or can't know the full spectrum of risks right away. Thalidomide, for example, was (for the most part) believed to be safe in the mid-50s, and it wasn't until the early 60s that awareness of the issues began to set in. So I am being a bit facetious when I say "you first" -- if it suits your risk tolerance or if you are in exigent circumstances, sure thing, who am I to judge? But it doesn't suit my personal risk tolerance at this point in my life. (Maybe ask me in a few years when I'm old and sick ...)

2) In terms of "transhumanism" more generally ... I see great dangers and I fear what a society of transhumans combined with humans would be capable of (if we haven't started down that road already). If transhumans really become vastly superior to humans, what will the relationship between them and the old-stock humans look like? Yuval Noah Hariri said something to the effect of, the only model for this version of the world we have is the current relationship between humans and animals -- the track record there is not exactly great ...

So, it's partially the risks from the tech itself, and partially the downstream consequences for society.