Uncommon Descent Serving The Intelligent Design Community

Have we at last solved the question of how sea creatures moved to land?

Pacific leaping blenny/Courtney Morgans,UNSW

So you’d think, reading this:

“This terrestrial fish spends all of its adult life living on the rocks in the splash zone, hopping around defending its territory, feeding and courting mates. They offer a unique opportunity to discover in a living animal how the transition from water to the land has taken place,” says Dr Ord, of the UNSW School of Biological, Earth and Environmental Sciences.

First, they studied the camouflage patterns of five different populations of the fish and found that in each case, the fish was camouflaged to match the rocks. They then made plasticine models and put them on the rocks, then more visibly on sand. Sure enough, birds, lizards and crabs attacked the models placed on sand more often. And, as it happened, the blenny camouflage patterns that protected them against a background of rocks resembled those of fully sea-dwelling fish and fish that spend some time on land (all of which also presumably camouflage themselves against rocks).

“These species provide an evolutionary snapshot of each stage of the land invasion by fish,” says Dr Ord. The similarities in colour between these species and the land-dwelling fish suggest the ancestors of the land-dwelling fish already had a colouration that matched the rocky shoreline before they moved out of the water, which would have made it easier for them to survive in their new habitat.

Hold it, we haven’t demonstrated very much here at all. The big sea-to-land problems do not involve camouflage, but adjustment to air breathing. The researchers acknowledge that, re the blenny: “It remains on land all its adult life but has to stay moist to be able to breathe through its gills and skin.”

In short, the blenny, dependent on tidal pools to breathe, never became a terrestrial species of the sort whose origin we are seeking. Never in its entire history so far did it do that.

The blenny is in reality an example of how an essentially aquatic creature can adapt to spending most of its time on land, as long as it can breathe in water. A piece in the puzzle yes, but not the one we are looking for: That would be a creature in the act of moving from life in the water to life on land, which is currently transitioning from gills to lungs. Doubtless such creatures have existed; the blenny, as it happens, isn’t one of them.

In today’s media environment, when seeking information about origins, we find big problems shoved under the carpet while pretending that a minor, interesting find helps answer questions. Camouflage was never a big part of the water-to-land puzzle.

See also: Land-based fish helps researchers assess how animals moved to land – and stayed there

Lobbing a grenade into the tetrapod evolution picture

First of all, a fact is defined as 'a truth know by experience or observation'. Second, the 'twisty logic' is simply pointing out 'the fact' that the fossil record evidence exclusively demonstrates that bauplan evolution (the skeletal system) is top-down. Here is the problem: there appears to be only a handful of lobe-finned fish remaining on the planet, from which to draw experience and observations, and no lobed-finned fish has been observed to get any closer to a semi-terrestrial life than the lung fish. Like all vertebrates, the most derived lung fish species are characterized by skeletal system reductions and simplifications (adopting an eel-like form, in addition to reducing the limbs/fins to filament-like structures); and, the extent of their terrestrial life consists primarily of estivation. The fact is, all known semi-terrestrial fish are at the waters edge, and none show potential of making the transformations necessary to advance to more terrestrial life- anatomically, ecologically, or physiologically. Insofar as Tiktaalik goes, the beast appears to have been a very large, slow fish that laid on the bottom of the substrate and preyed upon fish by striking from below. Anyhow, as you should know, the timing of Tiktaalik was upset when the 400 MYa tetrapod track-way in Poland were uncovered. Based on the tangible evidence, your assertion that the lobe-finned fish to tetrapod sequence is very well documented, is actually very weak and extremely unlikely, at least in the absence of a design model. If you are interested in discovering how the vertebrate skeletal system evolves, look at the skeleton of a whale or dolphin. They provide for a dramatic illustration of how bauplan evolution proceeds. Finally, if tetrapods evolved from fish, we should find multitudes of fish species living today, still in the water, pre-adapted for terrestrial life, with jointed appendages, exemplifying the simple lever and pulley systems exploited by most or all tetrapod lineages. No. Not. One. The power of fin to limb evolution is by necessity, and by contingency of common descent. littlejohn
The point is this: skeletal system reduction and the resulting deep time pattern of bauplan simplification, is observed across the animal kingdom with law-like regularity; therefore, the hypothesis and/or assertion that lobe-finned fishes are the direct ancestors of tetrapods is a contradiction of the observed evidence. That's some twisty logic. Prior plausibility is important in assessing evidence, and I guess you could make the case the evolution of tetrapods is implausible. But you then have to look at the very well documented evolution of tetrapods. When you do that there is little doubt about the fact tetrapods are lobed-finned fish. (And anyone who wishes to argue that is welcome to draw the bright white line between fish and tetrapods amon all those fish-a-pod species!) wd400
We are not closely related to either, and may not be related at all. The point is this: skeletal system reduction and the resulting deep time pattern of bauplan simplification, is observed across the animal kingdom with law-like regularity; therefore, the hypothesis and/or assertion that lobe-finned fishes are the direct ancestors of tetrapods is a contradiction of the observed evidence. By the way, I read one researcher that suggested that Ichthyostega and Acanthostega may very well be the product of returning to the water, rather than leaving the water. littlejohn
Of course, we aren't very closely related to ray-finned fish like blennnies. The fish we are closely related to (lobe-finned fish) to have "pre-aptatins" to life on land and fish-a-pods like Tiiktalik had wrists and (in Ichthyostega, Acanthostega ...) limbs. wd400
wd400 If you examine the skeleton of modern fish making an amphibious living today, such as the blenny, you will find that evolution has only acted to reduce or modify pre-existing skeletal elements. The blenny has no legs, and this is the common deep time evolutionary theme (loss of limbs/appendages). In fact, if memory serves me correctly, Tiktaalik appears to have lacked legs (at least the hind fins and/or pelvic girdle are absent in the fossil remains), and all the hoopla is in regards to specimens fore-fins, and the 'imagined' homologies to tetrapod fore-limbs. Aquatic invertebrates that presumably adopted a fully terrestrial living, were pre-adapted with fully developed limbs as aquatic animals. Then, after coming to shore, reduced both the number of appendages, and the skeletal elements that form the appendage. Obviously, we still find a great diversity of both aquatic and terrestrial invertebrates with limbs very similar to the form they had when they first appear. Furthermore, birds and bats did not add a pair of limbs to evolve flight, rather, they either maintained and modified the primitive number of skeletal elements, or reduced pre-existing elements by loss or fusion. The point being, the evidence for making more complex bauplans(the skeletal system, or general form, within known lineages, is imagined rather than observed. In conclusion, if we carefully examine the evolutionary history of the skeletal system within lineages, the fish to tetrapod hypothesis is more than likely a 'once upon a time story', that has not been validated by the fossil record, and resulted from a preconceived necessity of the current evolutionary dogma. Although it is certainly possible that tetrapods have fishy origins, it is surely not plausible, and a very weak explanation of tetrapod origins based on the tangible evidence. littlejohn
tjguy That sounds awfully like "why are there still monkeys". Tiktaalik and the other fish-a-pods wheren't evolving as part of some plan to take over the land. They were just making an amphibous living, like many fish do today. The fact many fish breath air tells us there are viable intermediates between gill-breathing and lung-breathing. In fact, bony fishes developed lungs before they developed swim bladders, so I don't think News' claim that the "adjustment to air breathing" was a major problem for tetrapod evolution can be taken too seriously. wd400
Evolution Cartoon - Waiting For That Beneficial Mutation - video http://www.youtube.com/watch?v=71-QYtxi8Bw bornagain77
wd400 says:
That’s not a particularly big prblem, lots of entirely aquatic fish breath air
Good point, but that doesn't solve your problem. That doesn't prove that random evolutionary processes can produce such abilities. Just because something exists does not mean it evolved. Existence does not prove anything. There is an alternative to the fish to land and land to fish scenario. Perhaps, just perhaps, they were designed/created to function in this environment. After all, they haven't proceeded to become a land dwelling organism. They seem quite happy being blennys. tjguy
the big sea-to-land problems do not involve camouflage, but adjustment to air breathing. That's not a particularly big prblem, lots of entirely aquatic fish breath air wd400

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