A critique of BibleLife.org’s article about bird evolution

Isn't nuclear fusion a form of radioactive decay?

We have many fossilized remains of humans who lived thousands of years ago. If humans actually lived for centuries there would be evidence of these long lives in the fossil record. Why isn't there?

You never actually did prove there was even oxygen in the past from a previous question.

Other way around - fission is decay. Fusion is adding of two lighter elements together to make a heavier one.

Decay do occurs in certain reactions when the fused nucleus is unstable. For exampe, in a hydrogen-hydrogen reaction, one of the proton transmutes into neutron and releases a positron and a neutrino, through β+ decay. In a deuterium-tritium reaction, He-5 is produced, but has a half-life of only a fraction of a milisecond, and emmits an electron.

Earliest feathers fan controversy

[IMG]http://news.bbc.co.uk/olmedia/800000/images/_802009_***300.jpg[/IMG]
The features look like feathers


A small, lizard-like creature that lived 220 million years ago has re-ignited the debate about the evolution of birds by seriously questioning whether they evolved from dinosaurs. Researchers studying the fossil remains say the animal, Longisquama insignis, had elongated structures on its back and arms that look very much like the feathers of modern birds. This suggests an evolutionary link between the two.
But Longisquama, the scientists say, was not a dinosaur, and in any case was around when the great reptiles had only just begun to walk the Earth.
And they argue that it is unlikely that features as complex and specialised as feathers evolved more than once.
Entrenched view
"These are some amazing fossils, and at the very least they prove that feathers did not evolve in dinosaurs," said Professor John Ruben, of Oregon State University and one of the scientists investigating Longisquama.
"The supposed link between dinosaurs and birds is pretty entrenched in palaeontology, but it's not as solid as the public has been led to believe."


Longisquama insignis appeared 75 million years before Archeopteryx


He added: "Feathers are a very complicated structure. The odds of them evolving first in Longisquama and then separately at some later point in dinosaurs or any other group of animals would have been astronomically small." The OSU researchers, and colleagues, report their analysis of the fossils in the journal Science.
Old specimen
The Longisquama specimen was actually discovered three decades ago in central Asia by a Russian palaeontologist who specialised in insects.
When the scientist published the first report of the fossil in 1970, he described a row of long narrow appendages down the animal's back, interpreting them as a frill of extremely long scales.


The feathers would have evolved for flight rather than insulation


The Science authors, who have pored over every detail of the fossils, which include most of the skeleton except for the hind part, have now challenged this view. They think the appendages show some of the most recognisable features of a modern-day feather.
Developing feather
They have identified a long, thin tube called a "shaft" running down the centre of each appendage.
A short distance from the base, a dense row of fine strands called "pinnae" project from either side. Neither the shaft nor the pinnae are typically thought to be features of reptilian scales.
The shaft also comes to a point at the base and appears to poke into a follicle in the skin. These and other clues point feathers as the only logical explanation for the features, the scientists say.
The pinnae of modern feathers first develop inside a tube called a feather sheath and then unfurl as the feather grows. The Longisquama fossil shows a new feather that seems to be developing in just the same manner.
Flight not warmth
"We can identify certain structures in these fossils that you only find in feathers and just don't see anywhere else," said Terry Jones, also an OSU palaeontologist and a co-author of the study.
"So we're quite sure we're looking at the earliest feather. But beyond that, this animal looks like an ancestral bird even if you ignore the feathers. The teeth, pectoral structure, neck, and skull are just like those of birds."
The researchers think the feathers evolved for flight rather than insulation. Providing warmth is the more likely function of the downy feathers sported by some much later dinosaurs.
Longisquama probably glided, rather than flew, using its long aerodynamic forelimbs for steering.
Dr Alan Feduccia, a co-author from the University of North Carolina at Chapel Hill, who in 1979 proved for the first time that Archeopteryx, the earliest recognisable bird, could fly, said: "These are the earliest structures in the fossil record that can be called feathers.
"They pre-date the so-called 'fuzzy dinosaurs' from China by at least 100 million years. Here we show unequivocally that the earliest known feathers evolved in the context of flight and not thermo-regulation."

Former analysis of George Olshevsky, showed that Longisquama is the sister group of all other theropods and birds within Dinosauria and is thus, cladistically speaking, a dinosaur. It is the most primitive-known dinosaur with a furcula, the next most primitive is Protoavis.

George Olshevsky doesn't know why the researchers of Longisquama do so desperately want dinosaurs to be unrelated to birds. He noted: " Unfortunately, these workers overlooked or discarded without consideration the very real possibility that Longisquama is itself a very primitive small theropod, not merely an archosaur _ belonging to the sister group of herrerasaurian and more advanced theropods.

Please people. This was a very good thread with a great OP from Aggie. I also saw that Oncedeceived had a nice contribution to it, which could be discussed in depth. Why do you guys feel the need to completely ruin the thread by replying to dad? Let him start his own threads for his deranged rants.

Wow, this thread got popular. Maybe I’ll take Mocca’s advice and post it in the quiet thread at some point.


You may have been aware of this already, but Longisquama is considered the alternative bird ancestor for people such as Alan Feduccia who don’t accept birds as being descended from dinosaurs. In other words, there are a few paleontologists who discount dinosaurs as bird ancestors for the reasons you’re describing, although it’s only a minority of them.

However, there are a couple reasons why I don’t think Longisquama should be used as a reason to discount dinosaurs for this. The most significant of these is described at the end of the same article you quoted:


(From http://www.dinodata.net/DNM/theorryofbirdevo.htm )

If Longisquama is a primitive theropod, the only thing this would prove is that feathers first evolved in the Triassic rather than the Jurassic period, and reverted to a more primitive state in dinosaurs such as Sinosauropteryx. I consider this a plausible scenario, since the primary advantage of feathers in most small theropods was for display and insulation, so in them natural selection would have favored a form of feathers that served this purpose as well as possible. A similar, but smaller reversal appears to have taken place in flightless birds such as ostriches—their feathers lack the asymmetrical structure and interlocking barbules found in the feathers of most modern birds, even though they were almost definitely descended from an animal that had this.

As I said about the dinosaurian origin of birds in my OP, there isn’t any way to prove that this sort of reversal took place in nonavian dinosaurs, and it’s possible that another theory will eventually be proposed that provides a more logical explanation of how Longisquama fits into bird evolution. But right now, I think this theory is the best one that exists.

There’s one other theory about this that’s worth mentioning, though, simply because it’s been a major subject of debate among paleontologists. Its main proponent is David Peters, who has a completely different understanding of dinosaur and pterosaur evolution from almost anyone else. His theory is that feather-like structures predated dinosaurs, and evolved in the common ancestor they share with pterosaurs. In dinosaurs these structures would have been modified into feathers, while in pterosaurs they would have been modified into wing membranes and the hair-like skin covering that’s preserved in some pterosaur fossils. Peters has even claimed to discover evidence of feather-like structures in fossils of pterosaurs, although most paleontologists consider it more likely that he’s misidentifying discoloration of the rocks in which the fossils were found.

EDIT: I asked at a paleontology forum about the article you quoted, and the opinion of the people there was that the structures on Longisquama aren’t similar enough to feathers for this animal to be considered significant in bird evolution. The article you quoted makes them sound fairly similar, but I should mention this third possibility also since it seems to be the most common attitude among paleontologists.

Just to let you know why it’s taking me so long to respond, someone at the paleontology forum I mentioned has offered to find a peer-reviewed article analyzing the structures on Longisquama’s back. According to them, this article reaches the conclusion that these structures have only a superficial similarity to feathers, which was most likely the result of convergent evolution. The article’s probably going to be in PDF format, so as soon as I have it I’ll host it at my site and post a link to it here.