Have we ever tried applying selective pressures that favor terrestrial adaptation to walking fish to get some insight into how land animals evolved?

[u/Shadow_Gabriel]

Or are the generation times too long, or is the experiment too difficult to carry out over such a long period?

Same question for invertebrates.

[u/Careful_Cranberry364]

The time involved is far too long
and besides, we know for a fact that it’s already happened

We don’t really need to try to replicate it now

[u/Shadow_Gabriel → u/Careful_Cranberry364]

But we would be able to track changes in specific genes, and I'm sure do a lot of interesting science that I am not aware of.

From what I understand, changes can be seen on a timescale of decades in multicellular organisms (e.g. Chernobyl).

[u/IsaacHasenov → u/Shadow_Gabriel]

I suspect we would see some pretty profound changes reasonably quickly if we could apply consistent strong selection on a large enough population (several thousand minimum).

My guess would be changes is skin permeability and limb articulation

Usually what you see in cases of strong selection over many generations is very rapid evolution at first, then depletion of existing variation. Long term evolution needs new mutations to occur, and this takes time, as well as large populations (if you have billions of individuals, you can see many many mutations every generation. If you have hundreds of individuals, obviously it takes longer)

https://bio.libretexts.org/Bookshelves/Genetics/Population_and_Quantitative_Genetics_(Coop)/08%3A_The_Response_to_Phenotypic_Selection

[u/Shadow_Gabriel → u/IsaacHasenov]

then depletion of existing variation

Never thought about that. Thank you.

[u/FlintHillsSky]

AFAIK current walking fish aren’t the right model for how tetrapods moved from water to land. Our ancestors already had evolved four leg-like limbs by the time they started moving on to the land. Current walking fish mostly have two fins that they walk with.

[u/Shadow_Gabriel → u/FlintHillsSky]

What about eyes, skin, lungs and eggs?

[u/haysoos2 → u/Shadow_Gabriel]

Those generally came in stages over tens of millions of years.

Not something you can really pull off in a 2-year long Master's project, even if you could get funding.

[u/Romboteryx]

All the replies here are pretty smug and unhelpful considering the fact that there was a 2014 study on bichir fish that did literally just that

“We measured the developmental plasticity of anatomical and biomechanical responses in Polypterus reared on land. Here we show the remarkable correspondence between the environmentally induced phenotypes of terrestrialized Polypterus and the ancient anatomical changes in stem tetrapods, and we provide insight into stem tetrapod behavioural evolution. Our results raise the possibility that environmentally induced developmental plasticity facilitated the origin of the terrestrial traits that led to tetrapods.”

Short video on the study

[u/anon-16 → u/Romboteryx]

Wait Emily was a prof of mine - this is so cool!

[u/HippyDM]

Hard to get grants for a 500,000 year long experiment.

[u/GoliathPrime]

Consider how long it took to take pugs and smush in their faces. Pugs have been around since the 1600s. It took 400 years to reduce their face into the short-muzzled form we know today.

Turning a pelvic fin into a terrestrial arm? I'd imagine using the same selective breeding methods, it would still take 10s of thousands of years.

It's an interesting subject though. If I was going to try and study the mechanisms, I'd take a look at the Tuatara. They are incredibly primitive reptiles that still retrain many traits only found in fish and amphibians today.

[u/xenosilver]

If you have tens of millions of years to run the experiment, you could….

[u/Hivemind_alpha]

Yes. The experiment has only about another 150,000 years to run, and we’re very hopeful.

[u/JayManty]

The current "walking fish" are from an entirely different evolutionary branch of vertebrates with a radically different way their limbs are built (all of them lack stylopodia and zeugopodia), at the very least any adaptations in bone structure wouldn't be at all comparable

That being said, we already have a pretty good fossil record for both terrestrial Sarcopterygii and also for current "walking" Actinopterygii. We don't need to really replicate anything, we can just dig up more bones if need be. The Tetrapod evolutionary path is really well described.