Complex heritable traits are not only determined by changes in the DNA sequence. Scientists from the University of Groningen Bioinformatics Centre, together with their French colleagues, have shown that epigenetic marks can affect traits such as flowering time and architecture in plants. Furthermore, these marks are passed on for many generations in a stable manner. Their results were published in Science on the 6th of February 2014. It seems that a revision of genetics textbooks is now in order.
‘While in mammals epigenetic marks are typically reset every generation, in plants no such dramatic resetting takes place. This opens the door to epigenetic inheritance in plants: epigenetic changes that are acquired in one generation tend to be stably passed on to the next generation’, explains Frank Johannes, assistant professor at the GBIC and co-lead scientist for the Science study.
Johannes’s French colleagues have produced inbred strains of the model plant Arabidopsis, in which the epigenetic marks vary between strains although the DNA sequence is almost identical. Nevertheless, these strains show marked differences in appearance, which are passed on to later generations.
Seven generations in this paper. Don’t be so sure about the mammals either. The jury is still out on that one.
The authors are cautious in dealing with how epigenetics affects Darwinism:
The epigenetic markers may also affect evolution, independent of DNA sequence. ‘They cause variation on which natural selection can act’, Johannes explains. As such, traits caused by epigenetic variation may make an independent contribution to changes in a species. ‘Our findings were made using inbred strains, but we also have evidence that we can find some of the same epigenetic QTLs in wild populations of this species as well.’ This suggests it is not just a laboratory artefact but something that plays a role in nature.
In short, without study of a given situation, we cannot just describe all evolution to Darwin’s mechanism (natural selection acting on random mutation, understood as in this generation), as the sole or main cause.
Don’t kid yourself that the textbooks will be revised any time soon in North America. Textbook publishing is in the hands of a few conglomerates, scalping the property tax payer who is obliged to support the compulsory public school systems, however bad. The Darwin lobby helps prevent any serious evaluation of what’s in the biology books vs. what’s in reality. Younger teachers who are serious about education are simply abandoning textbooks and constructing curricula that teach students how to access what they need to know in the tsunami of new information. In fairness, a textbook could, of course, be written about that. Probably, the only one the student will ever need.
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