Walking Before Flying

An anonymous reader writes "BYU biostaticians report in Nature their genetic analysis of the insect, known as the 'walking stick', which apparently gives a contrapuntal example of reversible evolution. Called Dollo's Law, the principle holds that the same evolutionary pathway can never be backtracked, because of random mutations. But this insect class first had wings, lost them, then got them back again. So what's next for some humans: a happy return to dragging their knuckles?"

Comments

Contrapuntal?

[MacAndrew]

Gee, I don't think I've ever heard the word contrapuntal. Thank you, another small step in the evolution of my vocabulary. :)

"Return" to dragging knuckles??

[Shadow2097]

Apparently, whoever wrote that never met any of the jocks at my high school! ;-)

Back on-topic, it does open up a whole lot of new possibilities as far as evolution goes. The evolutionary tree that is so commonly displayed in high school (and some higher-level) biology books might need some major rethinking.

-Shadow

rapping knuckles...

[KDan]

Unlikely. The genetic difference between an insect leg and insect wing (according to these articles, see Google News for a lot more sources that came out with this days ago) is very slight, the result of a single set of genes that switch between a leg and a wing. The difference between hairy quadruped apes and intelligent biped humans is a bit more pronounced... and there's no evolutionary pressure to make us devolve back to being quadrupeds (apart from that coming from the direction of good ole' Dubya).

Daniel

Re:rapping knuckles...

[KDan]

That was part of one of the articles I read about this: They said that the same genes control whether wings or legs are well-formed, so when the wing is switched off, the genes in it are still protected from too much mutation until the wings are switched on again.

Then again, I'm by far no expert on the subject...

Here it is: http://www.newscientist.com/news/news.jsp?id=ns999 93269.

Researchers assumed wings could not come back once lost as the genes needed to create them would mutate beyond repair once the wings disappeared. But Whiting says there is evidence from the fruit fly Drosophila that the same genes contain instructions for forming wings and legs.

If the same were true for stick insects, there would be an evolutionary pressure to stop wing genes from mutating, even in the insects that did not have wings. Those genes could then be turned back on in the future.

Daniel

So maybe now...

[phagstrom]

we can learn the answer to the puzzle:

if a fly couldn't fly, would we call it a 'walk'?

Underlying assumptions

[scistu]

I guess this guy has looked at mutations in the stick insect genome and made inferences about the phylogenic tree relating the species. The underlying assumption in these sorts of approaches is known as the infinitely many sites assumption. This says that a mutation can only happen once in any place on the genome and once it has happened it cannot mutate back. This assumption, although reasonable in most cases, may not be valid here. It would be nice to know how much information was used from the genome in order to get an idea of the validity.

Laws of probability

[xayide]

From the article:

Dollo's Law ... is also known as the Law of Irreversible Evolution--which basically states that organisms cannot re-evolve along lost pathways, but must find alternative routes (because the same fortuitous train of mutational events, being totally random, will never repeat).

I was not familiar with Dollo's Law before reading this story, and I may be misunderstanding some nuance or other... However, if mutations are truly random, isn't it necessary that they at least have the possibility to recreate a lost pathway, no matter how complex?

Re:Laws of probability

[BCGlorfindel]

However, if mutations are truly random, isn't it necessary that they at least have the possibility to recreate a lost pathway, no matter how complex?

I believe it was more a prediction that if evolution operates as we expect, organisms would be unlikely to 'solve' an evolutionary problem the same way twice. It was not so much saying such an occurrance was impossible, but that it's occurance would out of keeping with the idea of evolution being pushed by random mutations.

That said, Dollo died in 1931, so modern discoveries like pretty much all DNA/genetic evidence wasn't available to him. I'm not sure here, but I don't think a lot of weight was put in Dollo's law anymore. Anyone out there know of reasons someone would even bother mentioning that their research contradicted Dollo's law?

Re:Laws of probability

[xayide]

Mmmmm... convergent evolution... I'm under the impression that Dollo's Law refers to organisms evolving the exact same pathways to solve the same problem twice. When species evolve convergently, or even when one species re-evolves a trait, the same problem is usually solved in very different ways.
This site has the best definition that I was able to find, but I'm not sure how much stock I would place in its accuracy.

Re:Laws of probability

[barawn]

A "law" in science is more of an empirical observation - a guideline or principle. Kindof like Moore's Law. In general relativity, there's the "Law of Cosmic Censorship" which states that you can't have a singularity without an event horizon cloaking it. A much better mathematical term for what some scientists tend to use "law" for is "conjecture" or "principle".

Is it poor wording? Yah, but using "law" to describe a proven theory is falling by the wayside, since very little is truly provable, so "law" is almost getting a comic connotation.

Newton's third law is even pretty much a "conjecture", since we know the strong form of it isn't true in all cases, and while the weak is holding extremely well, it's entirely possible it may not be completely true.

Just look at the GOP!

[Archeopteryx]

George W. Bush looks like he is about to start dragging HIS knuckles any time now.

What knuckles?

[Pflipp]

I want a tail.

*heh*

[oPless]

So what's next for some humans: a happy return to dragging their knuckles?

Well you yanks (mostly) voted him in!!!