Arctic Fossils Mark Move to Land
Fossil animals found in Arctic Canada provide a snapshot of fish evolving into land animals, scientists say.
The finds are giving researchers a fascinating insight into this key stage in the evolution of life on Earth...
The 383 million-year-old specimens are described as crocodile-like animals with fins instead of limbs that probably lived in shallow water.
Before these finds, palaeontologists knew that lobe-finned fishes evolved into land-living creatures during the Devonian Period.
But fossil records showed a gap between Panderichthys, a fish that lived about 385 million years ago which shows early signs of evolving land-friendly features, and Acanthostega, the earliest known tetrapod (four-limbed land-living animals) dating from about 365 million years ago.
In 1999, palaeontologists Professor Neil Shubin, from the University of Chicago, and Professor Edward Daeschler, from the Academy of Natural Sciences in Philadelphia, set out to explore the Canadian Arctic in an attempt to find the "missing link" that would explain the transition from water to land.
After several years of searching with very little success, they hit the jackpot in 2004...
The team found three near-complete, well-preserved fossils of the new species, Tiktaalik roseae, in an area of the Arctic called the Nunavut Territory. The largest measures almost 3m (9 ft) in length...
The creature shares some characteristics with a fish; it has fins with webbing, and scales on its back.
But it also has many features in common with land animals. It has a flat crocodile-like head with eyes positioned on top and the beginnings of a neck - something not seen in fish.
"When we look inside the fin, we see a shoulder, we see an elbow, and we see an early version of a wrist, which is very similar to that of all animals that also walk on land," said Professor Shubin.
"Essentially we have an animal that is built to support itself on the ground."
...
Professor Jennifer Clack, from the University of Cambridge, said that the find could prove to be as much of an "evolutionary icon" as Archaeopteryx - an animal believed to mark the transition from reptiles to birds. [Link added -JA]
Of course, now the
(Via Bacon Eating Atheist Jew.)
20 comments:
..and another piece of the evolutionary puzzle falls neatly into place.....
It's a good thing present day "scientists" can reconstruct what an animal looked like 400 million years ago by referring to existing species. Otherwise we'd have no point of reference.
asher: They didn't have to do a whole lot of reconstructing here. If you'd read the article, you'd see that they found 3 very good fossils. Here's a picture of one.
And yet from this week's The Jewish Press Letters we have "No transitional links or intermediate forms between various kinds of creatures have ever been found... the evolutionist claims that it took perhaps fifty million years for a fish to evolve into an amphibian. But, again, there are no transitional forms... Nowhere do we see animals with partially evolved legs, eyes, brains, or various other tissues, organs, and biological structures."
Who are we to believe ?!?
excellent documentary.
here
Oy vey.
Glad to see that so many people are taking notice of this story.
Also, isn't it amazing how evolutionary theory makes predictions and they are actually accurate and verified (not to mention veriafiable).
Some Guy,
Those Jewish press letters make my blood boil almost as much as this guy http://jewishphilosopher.blogspot.com/
does.
It's the pride, the self agrandizment, just for the ability to dogedly stick to an opinion that all facts point against.
That is surely the curse of faith; the greater the evidence one ignores, the more justified one may feel in adherence to the faith at all odds.
No, the creationist guys (the ones I talk to anyway) say "it doesn't prove anything, we have lungfish today, the layers are all wrong anyway so this creature is only 5000 years old and we like to stick to our dogma regardless of any evidence".
Oh yes, and that modern artifacts have been found inside coal, that noah had dinosaurs on the ark as well as all the animals and STILL found space for them & their food, and the 8 humans had time to care for them all, that fossilisation takes a few months (honestly), and that the serpant who talked to Eve had no legs when it did so (look at the pictures), but had it's legs taken away from it by God for talking to Eve. No difficulties with the evidence there then!
There had to be some reason for natural selection to "decide" that this fish should suddenly develop the "vestiges of front limbs" clearly anticipating it's progeny to make the leap onto land. Once the gills were in decline, it could then breathe through it's nose (note the ability to move it's head..a very unfishlike characteristic...quote from the NY Times)and manage to develop all the other traits of a land roving animal. This is science, kids.
Hey, I bet the dinasaurs all died out from their having AIDs. Smoking?
There had to be some reason for natural selection to "decide" that this fish should suddenly develop the "vestiges of front limbs" clearly anticipating it's progeny to make the leap onto land.
I think the idea is that the creature lived in shallow waters, where fins that worked like legs and a neck that allowed it to raise its head out of water would have been beneficial.
I saw Shubin on CNN yesterday. He said that the waters were full of predators. This forced some fish to the shallows to escape the larger predators. And land had plenty of food that wasn't available in the water. Insects were plentiful for instance, so were plants.
Please notice it's a University of Chicago professor who found that missing link. The Dean of Admissions mentioned this yesterday and said, "Yeah. Our professors do things like that." :) Many, many happy smiles; he gave a lovely speech!
chana said: The Dean of Admissions mentioned this yesterday and said, "Yeah. Our professors do things like that."
Brilliant... [snigger].
Chana: Are you applying there?
I was an Early Action candidate so I was admitted back in the fall; if it so interests you, you can read my application essay here. I've actually been writing a lot on the U of C admitted students blog recently, in addition to a couple scattered comments over at the U of C Applicants blog. :) Smiles. Yesterday was a visiting day, and the Dean welcomed us at Bond Chapel (Ted O' Neill, I think is his name) and said that little thing about how his professors do "that sort of thing." :)
chana,
Awesome! I know it's supposed to be a great school. I have a couple of friends in grad school there and I think they like it. Congratulations on your admission.
r10b:
Now my understanding is that Darwin's theory does not say that aminals "will" themselves new biological capabilities. In other words this fish did not, after discovering the benefit of lifting their head out of the water, struggle to do so over many generations which lead eventually to a change in their physical structure to allow it.
This part is true, but the evaporating pond story is highly unlikely. As you point out, it would have to be evaporating pretty freaking slowly. What's more likely is that they lived in a normal body of water, with deep parts in the middle and shallow parts near the shore. The shallow parts would have been advantageous due to the fact that the bigger predators couldn't get them there and they would have little competitions for the food available there.
Additionally, the ability to breathe oxygen from the air is a huge advantage since there's a lot more oxygen available there than underwater. This could have become much more important if the pond was overpopulated or the algae were dying out, when the oxygen level in the water would be declining.
Over (a LOT of) time, the fish who could reach the most food and escape the most predators would thrive. In this particular niche, that might have been the ones who could raise their heads above water and even climb out of the water temporarily in search of food or shelter from predation.
r10b:
Those changes, slow, minute and incremental, were "forced" in one way or another by environmental pressures (eat, don't be eaten) yet the creature survived millions of years before the new attributes were developed sufficiently to truly aid in it's survival.
It's true that the intermediate steps must usually be useful in order to develop to later steps. This is usually what happens. For example, in our legged-fish's case, one might picture its ancestor being a regular fish, but with slightly stronger, more leg-like fins than other fish. Perhaps they aren't as good at swimming than other fish, but they are a little better at catching food in very shallow water. Likewise, it's descendents with even more leg-like fins would be even better suited to the shallow waters, where there is no competition because there aren't yet any legged animals in that niche. This is a case where a half a leg (which is basically what our creature has -- a half leg, half fin) is better than no leg. In the land of the blind, the one-eyed man is king. In the shallow waters, the half-legged fish is king.
When I look at contemporary environmental pressures I see things dying because they can't adapt fast enough.
To be sure, lots and lots of species don't make it precisely because they can't adapt fast enough, no question.
And one other thing since I'm here; if natural selection operates randomly I don't see how the move toward a helpful trait in one generation would not be reversed to some degree in the next. So a fish developed a rudimentary wrist. It didn't develop by necessity. It developed by dumb luck. Even if more survived with that genetic tendency, dumb luck does not follow a path. There's no more reason to develop that new feature further than there is to undevelop it (e.g. Darwin's Finches).
Take our shallow water example. A fin that is 10% more leg-like is better than a regular fin. One that's 20% leg-like is better than 10%, etc. Ultimately, animals with 100% legs develop and walk onshore, where they stay and continue to evolve. An easier example to see is the eye. Eyes have evolved through many stages, but there are animals still alive with eyes from each of the stages. From a few cells that detect light, to an eye cup, which detects light and direction, to an eye cup with small opening that can focus, to an eye cup with a layer of water for protection, to an eye with a layer of water shaped like a lens, etc. I posted about the evolution of the eye before.
I can't see how the animal's system would know which of the slight mutations actually contributed to its survival and therefore "saved" it from genetic regression and allowed only progression.
It's a messy system, and there are often missteps along the way. For example, our retinas are "inside-out" compared to how one would expect them to be designed. The optic nerve actually blocks part of it because it attaches on the "wrong" side and our brains have to compensate.
Well I must return to further the evolutionary development of my waste-rainy-Saturdays gene.
It will only continue to develop if you use the rainy Saturdays to have a lot of unprotected sex. ;-)
I thought of one more thing. These questions you are raising are at the core of evolution. This is why Behe and his fellow IDers came up with the idea of "irreducible complexity," since if you could find something (a flagellum, an eye, a knee) which could not have conceivably evolved over many steps since either there could be no intermediate steps or such steps would be far too disadvantageous, you would have successfully disproven evolution. If they were able to find something, they'd be right. But they haven't. They merely point out things like the flagellum and claim that it's irreducibly complex and, although in some cases we don't know *exactly* how it evolved, it's generally pretty clear that it's conceivable.
At an amateur's first glance, for example, the eye could seem irreducibly complex. What good is a lens without a retina? What good the iris without the pupil? The answer is that they evolved together, and that we can see each step along the way by looking at existing organisms which have eyes/eyecups/eyespots at a given stage.
r10b said: Those changes, slow, minute and incremental, were "forced" in one way or another by environmental pressures (eat, don't be eaten) yet the creature survived millions of years before the new attributes were developed sufficiently to truly aid in it's survival.
That's not quite the right way of looking at it. The environment doesn't 'force' developments. It selects those attributes that are either an advantage or not a disadvantage to a creatures survival. If a creature has positive mutations that gives it an advantage then it is more likely survive long enough to have offspring and pass on that particular trait. If a creature has negative mutations then it is less likely to breed and pass on those traits. Therefore over time the positive traits will accumulate in a population.
It should be remembered that individual creatures do not evolve. You and I are not evolving - it's our populations that evolve over many, many generations. Also creatures do not chose to evolve. They are not evolving towards something.
r10b said: There's no more reason to develop that new feature further than there is to undevelop it.
'New features' are produced by natural selection if they are advantageous. If a mutation occurs that reverses a previous mutation & it is in some way advantageous then it will increase in the population. There is no direction in evolution. It is not possible for something to 'devolve'. That's just change, not a change of direction. Did land mammals 'devolve' into dolphins? No... the evolved due to natural selection... from land mammals they returned to the sea they evolved from...
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