A study out of Oxford University's Research Laboratory for Archaeology has revealed some surprising information about how quickly evolution happens.
Led by Prof. Greger Larson, the study honed in on the role of mitochondrial DNA in a well-established population of White Plymouth Rock chickens. Mitochondrial DNA is genetic material found inside the mitochondrion, a cellular structure that converts chemical energy derived from food into a compound called adenosine triphosphate (ATP), a form of energy useful to cells. In most cases, mitochondrial DNA is inherited from the mother.
The subject population of the study began some 50 years ago with seven partially inbred lines of White Plymouth Rock chickens. With this in mind, the Oxford study took blood samples from 12 chickens of the same generation, but from the most distantly related maternal lines.
Analyses of the birds' blood samples revealed that the mitochondrial genomes of the birds had mutated twice in just 50 years. Prior to this finding, scientists believed the rate of change in the mitochondrial genome progressed at about 2% per million years.
This study revealed that in this particular pedigree, evolution is happening at a rate 15 times faster than that.
In conducting their analyses, the scientists also found evidence of paternal leakage, meaning that some of the birds in the study inherited mitochondrial DNA from their father. This direct evidence of paternal leakage flies in the face of the previously held belief that mitochondrial DNA is exclusively maternally inherited.
One of the theories about mitochondrial DNA floating around the world of genetic research is that mitochondrial DNA evolves by way of a fast-moving, purification process whereby negative mutations are quickly selected against, thus resulting in an apparent increase in short-term rates of mitochondrial change.
Larson noted that because we tend to measure evolution over long time periods, we often fail to see that evolution is also happening quickly, and right under our noses. This study is a testament to that.