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Short Legs Win Evolution Battle


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Short Legs Win Evolution Battle

By Jeanna Bryner

LiveScience Staff Writer

posted: 16 November 2006

02:01 pm ET

 

 

In a reptilian version of "Survivor," lizards with longer legs ultimately get booted from islands by their short-legged opponents.

 

Countering the widespread view of evolution as an eon-long process, evolutionary biologists discovered that when island lizards were exposed to a new predator, natural selection occurred in a six-month period, first favoring longer and then shorter hind legs.

 

The findings are detailed in the Nov. 17 issue of the journal Science.

 

Brown anolis (Anolis sagrei) lizards spend much of their time on the ground. But as previous studies have shown, when a ground-dwelling, predatory lizard is introduced, the anoles scamper up trees. They switch to an arboreal lifestyle to escape being eaten.

 

Anoles’ long legs make them fast runners, giving them an advantage in a ground-based setting where not much balance is necessary.

 

Researchers led by Jonathan Losos of Harvard University studied brown anole populations on 12 small islands in the Bahamas. They introduced a larger, predatory lizard (Leiocephalus carinatus) to six of the islands, while keeping six other control islands predator-free.

 

The scientists counted, marked and measured lizards at the beginning of the study, after six months, and again after 12 months. After six months, the anole populations dropped by half or more on islands with predators. On predator islands, the anole survivors had longer legs than non-survivors, a result the scientists suggest is due to longer-legged lizards being faster runners and better able to elude capture by predators.

 

Tables turned, however, during the next six months. The surviving anoles became increasingly arboreal, spending much of their time in treetops. At the end of the six-month stint, measurements showed surviving anoles had shorter legs compared with non-survivors. There was no significant difference in leg length between surviving and non-surviving anoles on control islands.

 

Shorter limbs are better suited for navigating narrow tree branches, which the scientists figure helped the lizards evade becoming dinner.

 

The researchers think that, over a longer period of time, the anoles in the presence of a predator would evolve much shorter limbs.

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In a reptilian version of "Survivor," lizards with longer legs ultimately get booted from islands by their short-legged opponents.

 

Countering the widespread view of evolution as an eon-long process, evolutionary biologists discovered that when island lizards were exposed to a new predator, natural selection occurred in a six-month period, first favoring longer and then shorter hind legs.

 

The findings are detailed in the Nov. 17 issue of the journal Science.

 

Brown anolis (Anolis sagrei) lizards spend much of their time on the ground. But as previous studies have shown, when a ground-dwelling, predatory lizard is introduced, the anoles scamper up trees. They switch to an arboreal lifestyle to escape being eaten.

 

Anoles’ long legs make them fast runners, giving them an advantage in a ground-based setting where not much balance is necessary.

 

Researchers led by Jonathan Losos of Harvard University studied brown anole populations on 12 small islands in the Bahamas. They introduced a larger, predatory lizard (Leiocephalus carinatus) to six of the islands, while keeping six other control islands predator-free.

 

The scientists counted, marked and measured lizards at the beginning of the study, after six months, and again after 12 months. After six months, the anole populations dropped by half or more on islands with predators. On predator islands, the anole survivors had longer legs than non-survivors, a result the scientists suggest is due to longer-legged lizards being faster runners and better able to elude capture by predators.

 

Tables turned, however, during the next six months. The surviving anoles became increasingly arboreal, spending much of their time in treetops. At the end of the six-month stint, measurements showed surviving anoles had shorter legs compared with non-survivors. There was no significant difference in leg length between surviving and non-surviving anoles on control islands.

 

Shorter limbs are better suited for navigating narrow tree branches, which the scientists figure helped the lizards evade becoming dinner.

 

The researchers think that, over a longer period of time, the anoles in the presence of a predator would evolve much shorter limbs.

 

[slam] This is interesting stuff, but what different species did the lizard evolve into? Short legs, long legs, it's still a lizard. And what was it before it became a lizard?

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This is interesting stuff, but what different species did the lizard evolve into? Short legs, long legs, it's still a lizard. And what was it before it became a lizard?

Nice strawman there, Slammy.

 

Macro-evolution doesn't occur within a six-month timespan. To evolve into a different species would take millions of years (or, at the very least, much longer than one human lifetime). This experiment proved evolution, however, because the reptiles evolved into better versions of themselves in order to avoid becoming somebody's snack.

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[slam] This is interesting stuff, but what different species did the lizard evolve into? Short legs, long legs, it's still a lizard. And what was it before it became a lizard?

 

goddamnit, why can't you xtians get this through your heads?!?!?!?!?!?! You are NOT going to see a different species come about within a 6 month time frame, if it will ever evolve into another species. If you came back to the island in 10,000 years, yea, maybe, but maybe not.

 

Evolution is not about a cat giving birth to a dog and NEVER has been! Evolution is ONLY about change through time. Given enough time, and enough change, you will have diverse life. Change is sometimes brought about by a random mutation, but can also (and I think more commonly?) be brought about by enviromental change, such as a new predator.

 

But what if over the next 10,000 years these lizards keep evolving shorter and shorter legs untill all they have are stumps and they mostly slither around by movement of their rib cage, staying in the trees and eating bird eggs. When we exit the time machine, would you still say they are lizards, and not snakes?

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Evolution is a fact, not a theory. This article shows just how powerful a force it is in nature. The Theory of Evolution takes the fact of evoltuion and proposes a model of how speciation occurs over time. Of course there are competing and complimentary theories within the ToE such as Puncuated Equalibria, which has periods of relatively short bursts of evolution causing diversity (10,000 years versus a million), but this does not change the fact of evolution occuring. Evolution is as much a fact of nature as gravity.

 

Slam, could you please define for us your use of the term "speicies"? I'm curious if you are calling something that scientists call 'speciation' something different to avoid a collision with your Bible-based Belief of Creationism? (The BoC, I think I'll call it from now on in converstation to distinguish it from the ToE).

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[slam] This is interesting stuff, but what different species did the lizard evolve into? Short legs, long legs, it's still a lizard. And what was it before it became a lizard?

Who said anything about a new species? :Hmm:

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This is interesting stuff, but what different species did the lizard evolve into? Short legs, long legs, it's still a lizard. And what was it before it became a lizard?

Nice strawman there, Slammy.

 

Macro-evolution doesn't occur within a six-month timespan. To evolve into a different species would take millions of years (or, at the very least, much longer than one human lifetime). This experiment proved evolution, however, because the reptiles evolved into better versions of themselves in order to avoid becoming somebody's snack.

 

[slam] Right, this is micro-evolution. Some variations within species have longer and shorter this and thats. I don't have a problem with this. It's evolution between DIFFERENT species that is problematic.

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[slam] This is interesting stuff, but what different species did the lizard evolve into? Short legs, long legs, it's still a lizard. And what was it before it became a lizard?

 

Evolution is not about a cat giving birth to a dog and NEVER has been! Evolution is ONLY about change through time. Given enough time, and enough change, you will have diverse life. Change is sometimes brought about by a random mutation, but can also (and I think more commonly?) be brought about by enviromental change, such as a new predator.

 

[slam] Could you explain how a predator, or any enviromental factor for that matter, can effect morphological change in a creature? Also, mutations are rarely beneficial and not one, or millions, have ever been shown to create new speciation.

 

But what if over the next 10,000 years these lizards keep evolving shorter and shorter legs untill all they have are stumps and they mostly slither around by movement of their rib cage, staying in the trees and eating bird eggs.

 

[slam] Somewhere between a long moving rib cage and stump legs the creature would find survival very difficult, don't you think?

 

When we exit the time machine, would you still say they are lizards, and not snakes?

 

[slam] They are the same species. Some reptiles have legs, others long oscillating rib cages.

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When we exit the time machine, would you still say they are lizards, and not snakes?

[slam] They are the same species. Some reptiles have legs, others long oscillating rib cages.

You really don't understand what modern science really, in fact teaches about the ToE. Again, you are incorrect in you saying they are not different species, which is why I asked you to define what "species" means to you. They in fact would be a different species. They would be incapable of breeding with other lizards.

 

If according to the context in which you are comparing the lizard with a new type of snake species, saying they would be the same species, then Slam... we are all the same species of sponge: from the ancient sea sponge itself, to the jelly fish, to the red snapper, to the crab, to the dragonfly, to the dog, to the goat, to the ape, to the human. This lizard would have in fact become a different species through the process of natural evolution. It would no longer be able to bread with its ancestors. If he is the same species by virtue of having evolved from a lizard originally, then we are all the same species: animals.

 

Getting a handle on what science means by "species" might help shed some light on this seemingly errarnt science that 99% of the scientific world accepts as a fact.

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Evolution is a fact, not a theory. This article shows just how powerful a force it is in nature. The Theory of Evolution takes the fact of evoltuion and proposes a model of how speciation occurs over time. Of course there are competing and complimentary theories within the ToE such as Puncuated Equalibria, which has periods of relatively short bursts of evolution causing diversity (10,000 years versus a million), but this does not change the fact of evolution occuring. Evolution is as much a fact of nature as gravity.

 

[slam] I am aware of only two theories: gradualism and punctualism. Regardless which one, there still is the problem with mechanism. Gould said that natural selection and mutation are not the cause of new speciation. If I'm not mistaken, the current theory has something to do with alleles and frequency. Whatever, no one has ever observed one major kind evolve into a different major kind.

 

Slam, could you please define for us your use of the term "speicies"? I'm curious if you are calling something that scientists call 'speciation' something different to avoid a collision with your Bible-based Belief of Creationism? (The BoC, I think I'll call it from now on in converstation to distinguish it from the ToE).

 

[slam] My understanding of species is what the Bible uses as "kinds." I would further say that a species or kinds are not capable of major changes that would cause them to become kinds or species other than what they are. Of course, there is wide variation within each kind or species. Macro-evolution is a term used by many to describe this major change in species.

 

I still would like to know what Gould ment by species level, larger groups and higher taxa.

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[slam] My understanding of species is what the Bible uses as "kinds."
Well that's not very clear. What do you mean by kind?

I would further say that a species or kinds are not capable of major changes that would cause them to become kinds or species other than what they are. Of course, there is wide variation within each kind or species.
This seems to be the fallacy of equivocation, but I've never been good with that fallacy.
Macro-evolution is a term used by many to describe this major change in species.

Macro evolution is a term used by evolutionary creationists and the like because they cannot deny changes occur within a species, but they do not accept that these changes can accumulate over a long period of time resulting in a separate species. Scientifically, there is no micro and macro evolution, there is just evolution.
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[slam] My understanding of species is what the Bible uses as "kinds."

Well that's not very clear. What do you mean by kind?

 

Macro evolution is a term used by evolutionary creationists and the like because they cannot deny changes occur within a species,

 

[slam] What kind of changes?

 

but they do not accept that these changes can accumulate over a long period of time resulting in a separate species. Scientifically, there is no micro and macro evolution, there is just evolution.

 

[slam] This is like saying there is just science. I think you're obscuring the issue. There must be some term that explains how major kinds evolve into something different.

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Slam I don't know if this is the right place to try and engage you in debate. If it's not I hope a moderator will inform me of that.

 

Let me ask you Slam if you accept these two statements as fact.

 

1) Organisms reproduce with heritable variation.

2) Many more organisms are born than will survive to reproduce.

 

Do those two statements seem reasonable or thruthful to you?

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[slam] What kind of changes?

Genetic (and epigenetic) changes which affect the ability to reproduce, including living long enough to reproduce. This means that the changes have an effect on the phenotype.

[slam] This is like saying there is just science. I think you're obscuring the issue. There must be some term that explains how major kinds evolve into something different.

Speciation, which is a very common term in evolutionary literature. This just hardens my belief that you have not actually done any research aside from reading anti-evolutionists' writings.

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