Cheers!
Posted on 11/10/2009 10:54:53 AM PST by decimon
CORVALLIS, Ore. - Penguins that died 44,000 years ago in Antarctica have provided extraordinary frozen DNA samples that challenge the accuracy of traditional genetic aging measurements, and suggest those approaches have been routinely underestimating the age of many specimens by 200 to 600 percent.
In other words, a biological specimen determined by traditional DNA testing to be 100,000 years old may actually be 200,000 to 600,000 years old, researchers suggest in a new report in Trends in Genetics, a professional journal.
The findings raise doubts about the accuracy of many evolutionary rates based on conventional types of genetic analysis.
“Some earlier work based on small amounts of DNA indicated this same problem, but now we have more conclusive evidence based on the study of almost an entire mitochondrial genome,” said Dee Denver, an evolutionary biologist with the Center for Genome Research and Biocomputing at Oregon State University.
“The observations in this report appear to be fundamental and should extend to most animal species,” he added. “We believe that traditional DNA dating techniques are fundamentally flawed, and that the rates of evolution are in fact much faster than conventional technologies have led us to believe.”
The findings, researchers say, are primarily a challenge to the techniques used to determine the age of a sample by genetic analysis alone, rather than by other observations about fossils. In particular, they may force a widespread re-examination of determinations about when one species split off from another, if that determination was based largely on genetic evidence.
For years, researchers have been using their understanding of the rates of genetic mutations in cells to help date ancient biological samples, and in what’s called “phylogenetic comparison,” used that information along with fossil evidence to determine the dates of fossils and the history of evolution. The rates of molecular evolution “underpin much of modern evolutionary biology,” the researchers noted in their report.
“For the genetic analysis to be accurate, however, you must have the right molecular clock rate,” Denver said. “We now think that many genetic changes were happening that conventional DNA analysis did not capture. They were fairly easy to use and apply but also too indirect, and inaccurate as a result.”
This conclusion, researchers said, was forced by the study of many penguin bones that were well preserved by sub-freezing temperatures in Antarctica. These penguins live in massive rookeries, have inhabited the same areas for thousands of years, and it was comparatively simple to identify bones of different ages just by digging deeper in areas where they died and their bones piled up.
For their study, the scientists used a range of mitochondrial DNA found in bones ranging from 250 years to about 44,000 years old.
“In a temperate zone when an animal dies and falls to the ground, their DNA might degrade within a year,” Denver said. “In Antarctica the same remains are well-preserved for tens of thousands of years. It’s a remarkable scientific resource.”
A precise study of this ancient DNA was compared to the known ages of the bones, and produced results that were far different than conventional analysis would have suggested. Researchers also determined that different types of DNA sequences changed at different rates.
Aside from raising doubts about the accuracy of many specimens dated with conventional approaches, the study may give researchers tools to improve their future dating estimates, Denver said.
Collaborators on the research included scientists from OSU, Griffith University in Australia, the University of Auckland in New Zealand, Massey University in New Zealand, University of North Carolina in Wilmington, the Scripps Research Institute, and Universita’ di Pisa in Italy.
The studies were supported by the National Science Foundation, National Geographic Society, and other agencies. About the OSU College of Science: As one of the largest academic units at OSU, the College of Science has 14 departments and programs, 13 pre-professional programs, and provides the basic science courses essential to the education of every OSU student. Its faculty are international leaders in scientific research.
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Thanks decimon. |
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Great stuff.
For example one could see a difference in a particular ERV shared between dogs and wolves that is X% different - and that X% difference is assumed to cover the time that dogs have diverged from wolves. The X doesn't change, it is a measured amount (for those particular sequences).
What the research is attempting to change is the amount of TIME that it would take for an X% difference to form; they say that X% that would be 20,000 years should be 40,000 to 60,000 years.
That means that the RATE of change is one half to one third as rapid as previously expected; not twice or three times as fast - as is also maintained, despite the inherent contradiction.
As I said, somewhere between the actual science and the publication of this in the school paper; someone got confused.
Not the amount of change but the number of changes.
A man who dates carbon wastes time.
The number of changes adds up to the amount of change.
A 13% divergence in an ERV sequence shared between two species that is 1000 bases long is a “number of changes” of 130.
But each change is one state of evolution. If there are many more changes than has been believed then the rate of evolution is faster than has been believed.
Are you following?
Say that previously a 10% difference in a particular DNA region between two species of a particular type and generation time (say two types of badgers) was assumed to correspond to a 10,000 year difference should be 20,000 or 60,000 BASED upon their penguin data.
The “rate of evolution” would be SLOWER, if that 10% difference took some 40,000 years instead of 10,000.
Why are we back to this? It is not a difficult concept. I thought we had moved on to EXPLAINING how they could claiming both contradictory things. Why am I having to explain the contradiction again?
I'm following you doing everything to promote your own thesis and nothing to understand the article.
Is it also my own thesis that one third is a slower rate not a faster rate?
OK then.
I consider my very own thesis to be supported by the evidence and the most rudimentary mathematics, therefore anyone who disagrees with my own thesis must not be able to think their way out of a wet paper sack.
Cheers!
Buttering me up? I hope it’s real butter. ;-)
Let’s say that it’s been believed that you finished off 100 servings of popcorn over the past 20,000 years (hence the grey whiskers). But it’s now believed that you finished off 2,000 servings of popcorn over the past 200,000 years. The rate of change of your popcorn consumption would thereby have increased by twice.
Substitute DNA changes for popcorn servings and you have it.
I’ve suspected for some time that something isn’t quite right with our DNA science. This may just be one thing that is wrong.
It would be nice to see more things reported as hypotheses rather than conclusions. But then, they might not be reported.
So basically what they are saying is that scientists have no idea what they are doing when it comes to dating techniques. Knock me over with a feature.
Yeah, it's the jocks that get all the action.
Any good scientist understands that any conclusion is merely tentative based upon the soundness of ALL of the underlying assumptions and ALL of the observed facts, and the change of any of these will likely change the conclusion. So what you hope, actually goes unsaid because it is already known to the professional audience that reads these papers.
Sorry GGG, but you cannot disprove the theory of evolution based upon genetic mutations by asserting that someone is mistaken about the rate of mutation, asserting that because the rate is slower than previously believed evolution is disproven. Your argument is an argument for a theory of evolution, just one with the rates jiggered, sort of like claiming Einstein was wrong because the speed of light is 20% slower than everyone thought it was.
That's one reason I'm not too critical of these articles. When there is a link to an original paper, that paper is often too much to tackle for a non-professional. The article is just someone's attempt to present the material in the paper to a general audience.
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