Shifting Icebergs May Have Forced Penguin Evolution

LiveScience via Yahoo ^ | 11/8/2005 | Ker Than

[kpp_kpp]

The breakup of giant icebergs may have forced minor evolutionary changes in penguins over the past 6,000 years, a new study suggests.

The Antarctic iceberg chunks, which break off the continent now and then, are thought to have blocked the swim paths of Adelie penguins returning home to their colonies. Some of the penguins were forced to become immigrants in other colonies, where they established new homes and interbred with the locals.

As a result, genetic changes that might otherwise have remained isolated became widespread among the different colonies. The result is what scientist call microevolution.

Other examples

Microevolution involves small-scale genetic changes in a species over time. The classic example is a color change undergone by British pepper moths in response to changing levels of air pollution. The acquisition of antibiotic resistance by bacteria and the trend towards tusk-less elephants in Africa are also examples of microevolution at work.

Because it is so well documented, even people who don't believe that evolution can lead to the creation of new species accept that microevolution occurs.

Most microevolution studies involve change over very short time periods, on the order of decades or a few hundred years. The detection of microevolutionary changes over longer time periods has been difficult because it requires that ancient DNA deposits be found together with samples from modern populations of the same species.

Adelie penguins may be the ideal candidates for such research. The penguins often live, breed and die in the same colonies where they were born and where their ancestors before them lived. And the remains of ancestor birds are well preserved in distinct layers of the frigid terrain, making fossil dating relatively easy.

For the study, the researchers extracted DNA from the bones of 6,000-year-old penguins and compared them to the DNA of their modern descendents. In particular, they looked at various genes made up of short stretches of repeat DNA sequences, called "microsatellite DNA."

Comparisons between the ancient and modern sequences revealed that the DNA sequences for some of the genes had gotten longer over time. The frequency of some of the different genes had changed as well: New variations had come into existence while others had been phased out.

Iceberg-driven evolution

One surprising finding was that there wasn't much genetic variation between different penguin colonies. Because adult penguins tend to return to the nesting colonies used by their ancestors, little interbreeding would be expected to occur between colonies. Over time, this would lead to genetic differences between colonies.

"Originally these colonies were almost certainly very different from each other," said David Lambert from Massey University in New Zealand, the principal investigator of the study. "[But] over time they've become the same."

Something was causing the penguins to break from their normal behavior and interbreed with members of different colonies. One idea was that the breakup of mega-icebergs was blocking the swim paths of penguins and forcing them to migrate to more accessible colonies.

To test their hypothesis, the researchers tracked the movements of nearly 10,000 penguins. The birds had been banded as chicks and came from three different colonies. In 2001, a section of the mega-iceberg B-15A grounded near the colonies. By tracking the banded penguins, the researchers discovered that many of them couldn't return to their home colonies. Some of the displaced birds were able to assimilate into other colonies and to interbreed with the locals.

The researchers think icebergs may have been a constant evolutionary pressure for the penguins and estimate that there have been about 200 such events within the past 10,000 years.

The study was detailed in the Nov. 7 issue of the journal for the Proceedings of the National Academy of Sciences.

[Sofa King]

"If a species or population develops a trait ( via survival, breeding, inheritance) then in what way have they not survived, bred, or passed on their genes...including trait X."

But does that trait make it more or less likely that an individual possessing it will survive and pass it on? If less, then it's a violation of natural selection.

"It's not a violation of natural selection if an organism, or group of organisms, fail to inherit any given trait, beneficial or otherwise...and if they did inherit the trait, and it's dominant, then you have another logical contradiction on your hands. The only other alternative is that the trait is recessive, which again, is not a violation of natural selection"

It is if failing to inherit that trait makes it less likely that they will survive and pass on their genes. That's the important part that you don't understand.

[csense]

But does that trait make it more or less likely that an individual possessing it will survive and pass it on?

Well, how do you know unless it survives long enough to reproduce. It seems to me that the conditions and terms define themselves, and in which case, prediction and testatbility are impossible.

....If less, then it's a violation of natural selection.

Then how do you account for any given organism inheriting such a trait. Unless we're talking about the carrier of the original mutation (first instantiation of whatever trait) which wouldn't violate natural selection, then you have another contradiction, and another circular argument.

It is if failing to inherit that trait makes it less likely that they will survive and pass on their genes. That's the important part that you don't understand.

You have no way of knowing what would be beneficial to new organisms. What may be beneficial to the parent, may not be beneficial to the offspring.

You're only standard for what may be considered beneficial, is whether or not the organism lives long enough to reproduce, and you only know that, when it happens.

[Sofa King]

"You're only standard for what may be considered beneficial, is whether or not the organism lives long enough to reproduce, and you only know that, when it happens."

Yes, so you observe and see whether or not it does. If it causes the organism to be less likely to pass on it's genes, but the percentage of the population that possesses that gene increases, then natural selection is falsified.

Can't see how that would happen? That's because it wouldn't. The fact that it doesn't is what shows natural selection to be true.

[csense]

Yes, so you observe and see whether or not it does. If it causes the organism to be less likely to pass on it's genes, but the percentage of the population that possesses that gene increases, then natural selection is falsified.

This is yet another logical contradiction. No offense, but I've had enough....

[Sofa King]

"This is yet another logical contradiction."

The logical contradiction here is that you're asking for an experiment that could prove natural selection to be false even if it was true.

The real problem here is it's so painfully obvious to you that natural selection is an accurate description of a natural process that any description of case where it doesn't happen seems absurd to you, and you are trying to use this very obvious truthfulness as grounds against it.

[csense]

The logical contradiction here is that you're asking for an experiment that could prove natural selection to be false even if it was true.

No.

I'm only asking that the terms of falsification be met. An observation which is contradictory in form, is unacceptable...for any theory.

[Sofa King]

"No."

Yes.

At first I thought that you were asking an honest question, but it has become clear that your misunderstanding is willful. Ask me to explain it to you again one day when you feel like making an actual attempt to understand the subject.

[csense]

Yes.

At first I thought that you were asking an honest question, but it has become clear that your misunderstanding is willful. Ask me to explain it to you again one day when you feel like making an actual attempt to understand the subject.

This from a person who posits that a trait can be both X and not-X. That is what I meant by form, and any reasonably intelligent person who's following this discussion, and absent any agenda, knows exactly what I'm talking about, and how any attempt to address this line of inquiry is either met with scorn, or a whole handful of logical contradictions and circular arguments. Some of you have such an entrenched belief system that you've all but abandoned logical principles, which is really where evolution completely breaks down, and which also explains why why there is such hostility toward philosophy in general. People like me, and other posters on this forum, ask questions that you guys can't answer, even the ones that talk the best story and pound the party line....and that scares the hell out of you

To be perfectly honest though, and after months of asking...I'm tired and frustrated, and think it's time to walk away a while...

[SunkenCiv]

Note: this topic is from 11/09/2005. Thanks kpp_kpp.

Here's a reprise from a post I made in Ancient Times:

In Horus vol II no 1, a journal published by the late David Griffard, Barry Fell was interviewed. Among other things:

We learned that seals were coming to a bad end and being mummified by nature in Antarctica in 1200 A.D. That was interesting and we wondered what was happening in Antarctica at that time...one of the technicians... noticed that a seal carcass that he himself had shot for dog-meat and that got left out through the winter... [looked] just like the mummified seals that they had been sending in. So without telling too many people what he was doing, he sent this mummified seal to be carbon-dated and do you know it was dated to 1200 A.D., and he had shot it the year before. When that was made public it really caused a storm...

We had two successive volcanic eruptions on the island of Tonga. There were human remains, then a layer of lava, then more human remains, then a layer of lava. We took charcoal out of both layers and had them both dated -- and we didn't tell them, the dating people, which layer which came from -- and to our amazement we learned that the whole island of Tonga has rotated through 180 degrees and is now upside down. The top layer is older than the bottom layer of the charcoal.

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