Posted on 11/09/2005 5:02:50 PM PST by 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.
from answers.com: evolution: Change in the genetic composition of a population during successive generations, as a result of natural selection acting on the genetic variation among individuals, and resulting in the development of new species.
I believe that natural selection is accepted by creationists. (most?) But the definition of evolution ends with the result being a new species.
Am I missing something that that natural selection is now being referred and officially termed micro-evolution? Is there a reason for this beyond the promotion of evolution into an area accepted by creationists?
Beware the penguins.........
i should have known that picture was coming on this thread.
When proponents of evolution decided to make natural selection synonomous with evolution.
Creationists realised there was confusion in the general public (encouraged by the MSM) over the the difference between natural selection/microevolution (which can be observed, tested, etc.) and "macro" evolution,)which can't be observed, tested, because it supposedly occurs over periods of millions, or billions of years, which is beyond the lifetime of a person to observe and test.)
Finally, someone who may be able to answer my question. If natural selection can be observed and tested, what physical event or process, does natural selection explain, that isn't already explained by mutation, drift, recombination, and heredity.
And that definition is in turn complicated by the need to define an equivalence relation for "species" (i.e. a definition with the property that, there does not exist any set of three animals X, Y, and Z such that X is of the same species as Y and Z, but Y and Z are not the same species as each other.).
Actually, even if one accepts a fairly tight definition of species, it's not inconceivable that a population which is geographically split into disjoint populations which are geographically incapable of interbreding (e.g. because an ice flow transported them too far apart) might, over enough succeeding generations, diverge enough to be called different species.
On the other hand, accepting that a rare combination of events could occur on occasion to produce a new species still leaves open the 'problem' for evolutionists that there is way too much diversity of life on this planet for such events to account for all of it (or even most of it).
you won't find me defending creationists trying to use natural science to prove God/the Bible/etc. but I'm not blind to the holes in evolution either.
"On the other hand, accepting that a rare combination of events could occur on occasion to produce a new species still leaves open the 'problem' for evolutionists that there is way too much diversity of life on this planet for such events to account for all of it (or even most of it)."
ironic that the age of the earth has gotten older the more we know about it yet there is still a conflict between what is statistically possible and the current accepted age of the earth (both in the underwhelming number of fossils and the overwhelming variety in the non-extinct species). it is almost as if there is a hidden dispute within evolution between the geological/astronomical determined age and the biological determined age. (ok maybe not so hidden)
is natural selection not just a term that takes all of those into account?
Processes like mutation, drift, recombination, and heredity contribute to natural selection because they affect how an organism co-exists with its own environment.
This is interesting. Creationists do not have any qualms with natural selection. We call it speciation, not evolution...certainly not macroevolution.
"I believe that natural selection is accepted by creationists. (most?) But the definition of evolution ends with the result being a new species."
This is the kind of hazy understanding of evolution that you get listening to creationists.
"Macroevolution" is nothing more than "microevolution" acting over a much longer period of time (making it hard to observe). There's no fundamental difference between the two aside from that. There is also no such thing as a definitive point in time when something becomes a new species. As I said on another thread:
"That's because defining a specie, from an evolutionary standpoint, basically involves drawing arbitrary lines to break up a smooth continuum. 'Species' are a human-imposed division used to make classifying things easier for study. There is no absolute natural definition for one."
Basically, after something microevolves long enough to be an obviously different type of organism, it gets called a different species and people look back and say that it macroevolved.
Well, if natural selection can describe any given genetic state, of any given population of organisms, then I don't see how it is either testable or falsifiable, let alone useful in a scientific theory.
"Dooo beee dooo beee doooo...."
No offense, but you're not making any sense here. 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.
As your statement stands, I don't think a logical contradiction is evidence of an observation that in principle could falsify natural selection.
If, for example, a culture of bacteria was routinely exposed to an antibiotic that it was previously immune to, it would be a violation of natural selection if that culture's future generations slowly started becoming susceptible to it's effects
Again, you're not making any sense.
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
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