Evolution in the short run is 15 times faster than in the long run

It is generally accepted that evolution “plays a long way”, and evolutionary changes in the mitochondrial genome do not exceed 2% per million years. This thesis has been clarified thanks to a new study on hens, conducted by a group of scientists led by Professor Greger Larson (Greger Larson) in the research laboratory of archeology at the University of Oxford.

They found in the mitochondrial genome of birds two mutations in just fifty years. Thus, the rate of occurrence of mutations in the mitochondrial genome of hens was 15 times higher than expected. The explanation is that some DNA changes subsequently “roll back”, therefore they are not noticeable when studying genome mutations over long time intervals.

After studying the genetic sequence of hens, scientists also found a copy of mitochondrial DNA, which was transmitted along the paternal line (shown by a blue arrow in the illustration). It is known that mtDNA is inherited only by the maternal line, and paternal leakage is extremely rare. Perhaps they still occur more often. In general, evolution is a much more dynamic thing than is commonly thought.



For research, scientists used the well-documented pedigree of many generations of hens, which is fifty years led by Professor Paul Siegel (Paul Siegel) from the Polytechnic University of Virginia. Selective mating of hens began in 1957 with seven partially related chickens - and since then information about the parents of each chicken has been entered into the database. Thanks to selection for half a century, we managed to achieve a ten-fold difference in the weight of 56-day-old chickens in two experimental groups.

Scientists have reconstructed mtDNA transmission over the past decades by taking blood samples from 12 hens of the same generation.

Professor Larson explainswhy their results are so different from the generally accepted notions of the rate of evolution: “Our observations show that evolution always happens quickly, but we don’t see this because we usually study it for long periods of time. Our study shows that evolution can occur much faster in the short term than we expected when studying fossil remains. It was previously assumed that the rate of change of the mitochondrial genome is about 2% per million years. With such indicators, we would not notice a single mutation in 50 years, but in fact, two were registered at once. ”

The large difference in the speed of short-term and long-term evolution can be explained. One theory is that “negative” mutations quickly disappear from the population, and only “positive”, useful mutations remain.

The scientific work is published in the journal Biology Letters.