Chou Toshio
Over9000
UNDERSTAND: The following thread is not meant to be a place to attack the theory of evolution or fuel any sort of Creationist v. Darwinist debate. Please check your religious questions at the door. This thread is meant to
answer earnest, honest, and scientifically-minded questions about Evolution. I have some honest questions, and I would like people with more scientific background to point me in the direction of research, findings,
or theories to help my understanding.
So with that out of the way, I'd like to post my question, the first of the thread:
QUESTION 1: Problems with Fish
So by the layman's understanding of evolution, about 400 million years ago, the first fish pulled themselves out of the water, and began their evolutionary journey to eventually become all the forms of land vertebrates that would conquer the world above water. Though they were not alone--
this was a world already colonized by lichens, mosses, and the first
primitive plants, which sustained a world dominated by the ancestors of millipedes, Scorpions, and other invertebrates. Fish were about to bring their speed-enabling vertebrates, keen eyes, and more developed brains to the land-- once they could get adapted. Then, once they did, amphibians,
reptiles, birds, and mammals--all descended from the same fish ancestor--would spread across the land, evolving into all the shapes we know today.
This is the story that's largely been told to us and largely accepted, but I have a bit of a problem wrapping my head around this story, and the
problem is in converging evolution.
Recently in the news, there was an article about how bichir have been raised on land, and proven themselves able to become better breathers and walkers based on their surrounding conditions-- this being a demonstration of how fish could evolve into land vertebrates. In fact there are several of species of fish with different degrees of amphibious abilities today; even with the land as dominated as it is by reptiles, birds, and mammals,
there are still niches for semi-amphibious fish such that they have convergently evolved in several instances from totally different lines.
Convergent evolution happens all the time, and we constantly observe it-- where totally different groups evolve similar attributes independently,boften due to similar environmental pressures or similar niches. The point is that when something works, nature tends to make it more than once. This can be seen in how octopus and fish evolved similar occular eye systems, or similarities in body structure between canid wolves, and the extinct marsupial wolves. Or how sharks and mammals both have penises.
So where was convergent evolution 400 million years ago when fish colonized the land? Why are all modern land vertebrates descended from the same line?
Why aren't there more groups of vertebrates with completely independent lineages, evolved from different fish? How could only 1 line, only 1 species succeed in producing all the lines of vertebrates that would dominate the world?
In the world where the first fish moved onto land, there must have been countless open niches and opportunities for this colonization to happen. Fish exist in all the worlds oceans, and after the Cambrian Explosion all the world's waters were full of life. So with all those oceans full of fish, and all the millions of rivers, streams, bays, inlets, beaches, and
countless land/water environments, there would have been endless opportunities for different fish in different places to make the move onto land. There should have been a huge number of lineages of amphibious fish,
and what's more, these lineages should have been given very prime opportunity to evolve independently of each other.
We're talking about fish just barely able to breath, minimum functionality for water retention, and locomotive abilities that would have been... terrible my modern standards. Even today's most successful modern animals
can take millions of years to colonize big expanses of the globe.
You can probably see what I'm getting at-- the world should have been ripe for fish to evolve into land organisms many, many times; and each of these lineages, separated by thousands of miles and great geographic barriers,
should have been given ample time to evolve independently. Water-tight skin and scales, muscles, lungs, speed, and power-- all the best adaptations of vertebrate animals should have had ample time to convergently evolve in completely different groups of vertebrates evolved from totally different fish in totally different parts of the world.
But even if they evolved into similar forms, it would have been impossible for them to interbreed-- just like it would be impossible for a marsupial wolf to breed with a canid wolf, coming from totally different lines of ancestry. It would not have been possible for their legacies to re-combine.
At the same time, life is so adaptable and evolution so powerful, it seems impossible to me that only one fish's lineage would survive, only 1 lineage
would persevere, and perhaps compete the others to extinction. Extinction just doesn't happen that easily, and colonization and intermingling of species don't drive entire evolutionary branches under. Just like Zebra (which evolved in North America) and Gazelles/Ampala co-exist in Africa today, you'd expect some species of both lines to survive and adapt around each other.
By the time the fully land adapted descendants of two different fish lineages met, they both should have sufficiently evolved and diversified such that some
species of both lines would survive.
But that's not what happened.
If that were to have happened, we'd see a far greater diversity of groups, with completely different genetic backgrounds. The reality is that you can count the main branches on 1 hand-- amphibians, reptiles, birds, and mammals-- with all extinct vertebrates we know also being descendants of
one of these lines; and scientists believing that ALL these lines came from one origin line-- one species of fish.
To me, that doesn't make sense. Convergent evolution happens so easily. Fish take on semi-aquatic forms in so many places and with so much ease, even in a world with fully terrestrial vertebrate competitors. The opportunity for different lines to form back then should have been far greater.
How is it possible that we didn't come up with a far greater number of vertebrate groups from completely different ancestries?
Whoever has the answer or can point out a reasonable scientific
explanation, please chime in.
Note: The question is NOT to challenge the view of a single fish ancestor-- the genetic testing probably supports it. The problem for me is that it seems wildly improbable for ONLY one fish lineage to have succeeded in colonization of the land. How did it happen that way?
answer earnest, honest, and scientifically-minded questions about Evolution. I have some honest questions, and I would like people with more scientific background to point me in the direction of research, findings,
or theories to help my understanding.
So with that out of the way, I'd like to post my question, the first of the thread:
QUESTION 1: Problems with Fish
So by the layman's understanding of evolution, about 400 million years ago, the first fish pulled themselves out of the water, and began their evolutionary journey to eventually become all the forms of land vertebrates that would conquer the world above water. Though they were not alone--
this was a world already colonized by lichens, mosses, and the first
primitive plants, which sustained a world dominated by the ancestors of millipedes, Scorpions, and other invertebrates. Fish were about to bring their speed-enabling vertebrates, keen eyes, and more developed brains to the land-- once they could get adapted. Then, once they did, amphibians,
reptiles, birds, and mammals--all descended from the same fish ancestor--would spread across the land, evolving into all the shapes we know today.
This is the story that's largely been told to us and largely accepted, but I have a bit of a problem wrapping my head around this story, and the
problem is in converging evolution.
Recently in the news, there was an article about how bichir have been raised on land, and proven themselves able to become better breathers and walkers based on their surrounding conditions-- this being a demonstration of how fish could evolve into land vertebrates. In fact there are several of species of fish with different degrees of amphibious abilities today; even with the land as dominated as it is by reptiles, birds, and mammals,
there are still niches for semi-amphibious fish such that they have convergently evolved in several instances from totally different lines.
Convergent evolution happens all the time, and we constantly observe it-- where totally different groups evolve similar attributes independently,boften due to similar environmental pressures or similar niches. The point is that when something works, nature tends to make it more than once. This can be seen in how octopus and fish evolved similar occular eye systems, or similarities in body structure between canid wolves, and the extinct marsupial wolves. Or how sharks and mammals both have penises.
So where was convergent evolution 400 million years ago when fish colonized the land? Why are all modern land vertebrates descended from the same line?
Why aren't there more groups of vertebrates with completely independent lineages, evolved from different fish? How could only 1 line, only 1 species succeed in producing all the lines of vertebrates that would dominate the world?
In the world where the first fish moved onto land, there must have been countless open niches and opportunities for this colonization to happen. Fish exist in all the worlds oceans, and after the Cambrian Explosion all the world's waters were full of life. So with all those oceans full of fish, and all the millions of rivers, streams, bays, inlets, beaches, and
countless land/water environments, there would have been endless opportunities for different fish in different places to make the move onto land. There should have been a huge number of lineages of amphibious fish,
and what's more, these lineages should have been given very prime opportunity to evolve independently of each other.
We're talking about fish just barely able to breath, minimum functionality for water retention, and locomotive abilities that would have been... terrible my modern standards. Even today's most successful modern animals
can take millions of years to colonize big expanses of the globe.
You can probably see what I'm getting at-- the world should have been ripe for fish to evolve into land organisms many, many times; and each of these lineages, separated by thousands of miles and great geographic barriers,
should have been given ample time to evolve independently. Water-tight skin and scales, muscles, lungs, speed, and power-- all the best adaptations of vertebrate animals should have had ample time to convergently evolve in completely different groups of vertebrates evolved from totally different fish in totally different parts of the world.
But even if they evolved into similar forms, it would have been impossible for them to interbreed-- just like it would be impossible for a marsupial wolf to breed with a canid wolf, coming from totally different lines of ancestry. It would not have been possible for their legacies to re-combine.
At the same time, life is so adaptable and evolution so powerful, it seems impossible to me that only one fish's lineage would survive, only 1 lineage
would persevere, and perhaps compete the others to extinction. Extinction just doesn't happen that easily, and colonization and intermingling of species don't drive entire evolutionary branches under. Just like Zebra (which evolved in North America) and Gazelles/Ampala co-exist in Africa today, you'd expect some species of both lines to survive and adapt around each other.
By the time the fully land adapted descendants of two different fish lineages met, they both should have sufficiently evolved and diversified such that some
species of both lines would survive.
But that's not what happened.
If that were to have happened, we'd see a far greater diversity of groups, with completely different genetic backgrounds. The reality is that you can count the main branches on 1 hand-- amphibians, reptiles, birds, and mammals-- with all extinct vertebrates we know also being descendants of
one of these lines; and scientists believing that ALL these lines came from one origin line-- one species of fish.
To me, that doesn't make sense. Convergent evolution happens so easily. Fish take on semi-aquatic forms in so many places and with so much ease, even in a world with fully terrestrial vertebrate competitors. The opportunity for different lines to form back then should have been far greater.
How is it possible that we didn't come up with a far greater number of vertebrate groups from completely different ancestries?
Whoever has the answer or can point out a reasonable scientific
explanation, please chime in.
Note: The question is NOT to challenge the view of a single fish ancestor-- the genetic testing probably supports it. The problem for me is that it seems wildly improbable for ONLY one fish lineage to have succeeded in colonization of the land. How did it happen that way?
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