That would be fine; but we have some lineages coming from fish living on the surface. Those are the interesting ones.

While metabolic advantage is a thing, I'm not sure if organisms are expected to carry minimum amount of genetic code that they actually use; in what little I know about developmental biology, I recall there's a high-level structure to the genetic code - some genes are doing more of flow control than encoding actual proteins. It's conceivable that the fish which walked on Earth was the one that managed to accumulate inactive adaptations for walking and switched them on.

Also, there's horizontal gene transfer to account for. It further complicates the picture.

> one that managed to accumulate inactive adaptations for walking and switched them on.

https://www.discoverwildlife.com/animal-facts/fish/can-fish-...

Genes get duplicated by accident, then accumulate mutations which are usually neutral or worse. Occasionally they help you achieve something slightly more useful than before. Lobed fins that helped you heave yourself back into water when you get beached would have helped. bigger lobed fins would help you get back when stranded further up the beach, or get from pool to pool. It's unlikely that an entire set of limbs, other necessary body upgrades to support them and neural circuits would just hang around waiting for all the right mutations to collect like hole punches on a restaurant loyalty card before some critter slapped their thighs and stood up and walked. Evolution does not plan ahead.

This argument is however an argument from faith and not from computability perspective. Random garbage genes flipped on won't grow a leg with intricate mechanical abilities. Those abilities have to be computed somewhere and need to be useful right from the start to appear in offsprings otherwise they get eliminated as a waste. Yet everyone puts their faith in some random process instead of pinning down the concrete mechanisms how does this happen. So you basically end up forcing some idiotic faith on everyone instead of digging deep and figuring it finally out. I would be more inclined to believe if you told me that pre-adolescent brain spends 25% of its computing capacity on figuring out how to improve its body and encoding it into genes instead of trusting some random mutation (likely error-corrected) to do the heavy lifting.

It's not a faith thing. Yes, metabolic advantage is a thing and useless adaptations can get eliminated over time (it seems to matter more in single-cellular organisms, though). However, often enough, unused adaptations can persist for a long time - for example, pythons still have the whole blueprint for "a leg with intricate mechanical abilities" and nerves and stuff, it's literally just switched off. We know because some researchers figured out how to flip it back on, and behold, snakes grew their legs back. That's what I've been alluding to in the prior comment - genes aren't encoding a flat blueprint, but a complex program with many genes working as flow control or signalling superstructure, able to toggle or modify whole complex body parts.

> I would be more inclined to believe if you told me that pre-adolescent brain spends 25% of its computing capacity on figuring out how to improve its body and encoding it into genes instead of trusting some random mutation (likely error-corrected) to do the heavy lifting.

this is an argument from personal incredulity. just because you are too dumb to understand how something works doesn't mean that your fantasy/sci-fi version is accurate. brains changing genes belongs in a discussion of Neal Asher's polity, not in a biology discussion.

So you are saying that e.g. a large mammal lifespan of 70 years is sufficient to generate as many good random mutations as needed to grow a new leg over 10,000 generations if necessary? Where is the evidence of a fast algorithm requiring so few selections to come up with a complex new organ? How is that not blind faith? Not sure who is the dumb one here...

> a large mammal lifespan of 70 years is sufficient to generate as many good random mutations as needed to grow a new leg

thankfully, nobody is claiming that happens. i can explain more, but there's the issue of my fees. £200,000 seems reasonable, given how dumb you are.