This statement is based upon a false premise that an organism can become “maximally adapted” to a given niche. They can’t. There’s always a way to improve, if building complexity is an available option (evolutionists must maintain it is).
It’s true there is experimental evidence of diminishing returns for beneficial mutations. That’s because these mutations don’t act well in concert with one another, but instead they tend to exhibit antagonistic epistasis. This in turn is likely because they aren’t acting together in a constructive fashion. They’re inherently reductive. None of this has to do with the environment. It has to do with the nature of how mutations damage or remove information.
Conceptually, you can always build up an organism and make it better, regardless of environment. Think about the supposed transition between single-celled and multicellular life. That could not have been necessary to adapt to any environment. Bacteria can survive everywhere that multicellular life can, and then some. Bacteria are the ultimate in “adapted life”, but that doesn’t matter. Because this whole idea that it’s all about environmental adaptation is just a false premise to begin with. That’s only a tiny slice of what’s going on in life.
And sometimes any improvement of one aspect necessitates a reduction somewhere else. If I make a crowbar longer it is a better lever, but it is also heavier and more awkward to carry. Is it better? That depends on what you are trying to do.
Why wouldn’t that be the case? The laws of physics must fundamentally constrain how effective a machine could become. There’s some minimum weight below which loss of material would weaken it’s structure, there’s some maximum amount of material above which it’s weight would become cumbersome. There’s some material that has the lowest possible degree of friction that is physically possible given the elements of the periodic table, etc. etc. At some point, considering what the machine is doing, it can’t become any better without that requiring a violation of the laws of physics. The shape can’t get any smoother, it can’t get any lighter, it can’t get any stronger, it can’t physically hold more fuel.
You’re speaking in terms of engineering for a very specific engineering goal. But life can achieve the same goal of competitive survival by means of an infinite number of possible pathways. You can’t artificially limit something to only one pathway. If the history of evolution is to be believed, then obviously life can take something that has evolved along one pathway and begin to take it down a completely different one, building new functions in the process. In other words, there’s more than one way to skin a cat. And no matter how good you are currently, there’s no reason you can’t be even better. The ultimate theoretical maximum in “survival competitiveness” would have to be immortality and omnipotence (becoming a god), and no life has ever reached that goal in any environment.
My point is that it’s nonsensical to talk about “maximum fitness”. Reproductive fitness is only ever relative. There is always a theoretical way to improve. Even if you’re on the top of the current food chain, you could have an improvement over that, and you’d get a new sub-population that could begin to beat out the previous winners. This is allegedly how evolution has managed to turn single-celled organisms into people. The difference between a bacterium and a human is almost as huge as the difference between a human and God. Our capabilities go so far beyond single-celled organisms that it boggles the mind to comprehend it.
But are we more reproductively fit? It doesn’t really make sense to say because we are adapted to life on entirely different scales and in different niches.
There are also local optima within a fitness landscape. To get to other fitness peaks it may require a too much of a reduction in fitness. It’s easy for human designers to do a total redesign, but evolution doesn’t operate that way. There can be historical contingencies that lock in a specific evolutionary pathway and a specific fitness peak.
Maybe it isn’t false, but just a deeply embedded misunderstanding about how we think about these sorts of things. After all, if you can’t refute it, maybe it is not wrong.
Duell may have said the same in 1889 to those who disagreed with his statement. After all, it’s much easier for him to say “No new inventions are possible” than it is for one of his audience members to prove him wrong. To do that, they would actually have to become an inventor and invent something!
In evolutionary terms, it’s harder still to refute, since we’re talking about millions of years.
The problem is virtually all of the things you’ve claimed as “self-evidently false” about evolutionary biology have already been demonstrated true beyond all reasonable doubt. Sorry but personal intuition just doesn’t cut it in the world of science no matter how much Axe preaches the position.
A crowbar can be modified by incremental measures to be an ever-better hammer, but this will not make it a better crowbar. In fact it will almost certainly make it a worse crowbar. Now if there exists a need for both then that’s fine, the ecosystem can support novelty. But if not, then different isn’t better. This is, by analogy, the issue that you are stuck on.
Sure, it is possible that a population could move towards increased complexity which might enable the exploitation of some novel niche, but this does not make that population ‘better’. Like the hammering crowbar, this more complex population is likely to be worse at doing whatever its ancestors did. But, again like the hammering crowbar, the ecosystem may have room to support the novelty in which case you can have a divergence between the ancestral type and the more complex population. The ancestral population would still be at an adaptive peak for whatever it is they do, and if the ecosystem still supports this it is unlikely that they will change all that much.
Is the complex population better? They are better able to exploit whatever the new niche is, certainly, but that doesn’t make them better in any absolute sense. And if the new niche is more fragile, then it is quite reasonable to say it is worse off as it faces a higher risk of extinction. So when discussing fitness, the discussion relates to fitness to the current niche.
This is actually fatal to your broader argument about GE with respect to empirical DFEs, as has been previously explained, because it means that all of the mutations that might be beneficial to the exploitation of some novel niche will still be considered deleterious if harmful in the current context.
Your “intuition” is leading you astray again. Evolution acts like a tracking loop which drives a population towards local optima in the fitness landscape. The population will approach these peaks asymptotically until the benefit of climbing even a little higher is outweighed by the costs. Of course when the fitness landscape changes as it almost invariably does the tracking then has much more opportunity to hill climb once again.
I’ve never seen humans live in almost boiling mineral springs at 95C, or breathe sulfur 7900 ft. below the surface, or survive huge doses of ionizing radiation, or survive 300G shocks like extremeophile bacteria can.
You seem to be confusing human ability to use technology which temporarily alters our local environment (say with space suits or jet aircraft to break the sound barrier) with the ability to survive unaided in vastly different environments.
Sorry, I still don’t agree with this. It still amounts to a claim of “everything that can be invented has been invented”. The idea that an organism can become “as successful as possible” in a given niche. And I do find such a claim self-evidently false. But since there’s no real way to make headway that I can think of, let’s just drop the issue.