The article, “Genomic Fossils Calibrate the Long-Term Evolution of Hepadnaviruses,” in PLoS Biology “marks the first time that endogenous hepadnaviruses have been found in any organism” (endogenous viruses can deposit fragments of themselves into chromosomes, allowing them to be passed down from generation-to-generation). Physorg reports that “[p]reviously, most of these known ‘fossilized’ virus sequences came from retroviruses.”
Then they utilized a “molecular clock” to determine approximately when that divergence took place.
Eddie Holmes, professor of biology at Penn State University, said, “The results they obtained were remarkable; whereas we previously thought of hepadnavirus evolution on time-scales of only a few thousand years, this paper shows that the true time-scale is in fact many million years. Therefore, hepadnaviruses, and likely many other viruses as well, are far older than we previously thought.”
“Genomic fossils like the remarkable hepadnaviral fossils . . . have the prospect of completely revising our preconceived notions about the age and evolution of such viruses,” said Harmit Singh Malik, associate member of the Fred Hutchinson Cancer Research Center in Seattle, Washington.
The authors arrived at their 19-million-year date by locating the fragments “in the same spot on the genome of five species of passerine birds” and assuming that there was a “common ancestor that lived more than 19 million years ago” to which they traced those five species. Then they utilized a “molecular clock” to determine approximately when that divergence took place. To calibrate the molecular clock, one must know the absolute age of some evolutionary divergence event, such as the split between mammals and birds. An estimate of the timing of this event can be gained by examining the fossil record, or by correlating this particular instance of evolutionary divergence with some geological event of known antiquity (such as the formation of a mountain range that split the geographic range of a species in two, thus initiating a process of speciation). Once the evolutionary rate is calculated using a calibration, this calibration can then be applied to other organisms to estimate the timing of evolutionary events. Using this method, it has been postulated that any two bird species are diverging from each other at a rate of 2% per 1 million years. This has long been regarded as a standard quantity in genetic studies of birds and is known as the “2% rule.”
Anyone notice more than a few assumptions in squeezing 19 million years out of the virus fragments here? We would argue that the original age of thousands of years is correct, and does not rely on mountains of speculation piled on top of pre-determined assumptions. God created both viruses and birds with huge genetic variability, and they have reproduced within their kinds to become . . . viruses and birds. No surprise there, but what is surprising is the “remarkable similarity” of alleged 19-million-year-old viruses to modern ones.
For more information:
- Evolution Exposed, Classifying Life
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