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Here's another example. It's a video by Carlos Guerrero-Bosagna an epigenetics researcher (post-doc) at Linköping University in Sweden. He works in the lab of Per Jensen. The video is full of misrepresentations and half-truths and gives a very misleading picture of the state of knowledge in the fields of gene regulation and evolution.
The main problem here is that, in my opinion, methylation and histone modifications are mostly consequences of regulation, not causes. Most regulation at the level of transcription is due to transcription factors binding to various sites near gene promoters. Those interactions can trigger associated epigenetic changes in those species that have them.1
There's hardly any evidence that these sorts of epigenetic changes can be passed on to subsequent generations in multicellular organisms. There are a few exceptions that are widely reported in the popular press but these exceptions are definitely not the rule. (And not all of them will survive fact-checking.)
There's no evidence that DNA methylation and/or histone modifications can be stably inherited for many generation and no evidence that they can affect evolution by becoming fixed in the population. DNA methylation and histone modifications are transient phenomena in those species where they occur.
Carlos Guerrero-Bosagna disagrees. That's fine. There is genuine scientific debate over these issues and I cannot say for certain that my view is the only possible answer. However, if we're talking about education (i.e. TED-Ed) then the correct version of the video would mention the fact that Carlos Guerrero-Bosagna is presenting a minority view that's contentious. In the absence of such a disclaimer, the video is not education, it's propaganda.
I came from the world of evolutionary biology. I have always been interested in evolutionary theory but I was never convinced by the neo-Darwinian argument that environmental factors are not a big player in the generation of genetic changes. On the other hand, I never understood the fierce dismissal and often mocking of the Lamarckian ideas in schools and universities; particularly, because Darwin himself never denied Lamarck’s ideas. In epigenetics I found the mechanisms that allow you to understand the action of environmental exposures on the genome.He also seems to have some concerns about DDT.
Then, if you open your mind to the idea that environmental factors can indeed influence the genome and also inheritance, then reproductive biology becomes the discipline of excellence to study if and how these effects can propagate to future generations. I would go further; several disciplines have acted as main contributors of ideas to evolutionary biology at different times in science history, starting with taxonomy, then statistics, genetics and developmental biology. I think reproductive biology will now become the main discipline contributing ideas to evolutionary biology, because it will consider the integration between environmental exposures and inheritance. Epigenetic mechanisms will be the main tool used to explain this integration.
Yes, I am absolutely sure that past developmental exposures to DDT and other compounds have contributed to the current high incidence of obesity in the US and other developed countries. One of the main reasons this is my belief is because we have observed this transgenerational tendency to obesity not only with DDT but with other compounds as well, including plasticizers. So, my thinking is that the DDT is only one component responsible for this transgenerational obesogenic effect.For more insight into his views see the recent paper by Guerrero-Bosagna and Jensen at Globalization, climate change, and transgenerational epigenetic inheritance: will our descendants be at risk?. Here's the abstract ...
What is interesting, and scary, is that people have been exposed to several of these compounds at the same time, and they generate somehow repeatable phenotypes, the strongest being obesity and ovary abnormalities such as polycystic ovary. Just as obesity, polycystic ovary incidence has experienced a tremendous increase in humans in the past decades.
Transgenerational epigenetic inheritance has gained increased attention due to the possibility that exposure to environmental contaminants induce diseases that propagate across generations through epigenomic alterations in gametes. In laboratory animals, exposure to environmental toxicants such as fungicides, pesticides, or plastic compounds has been shown to produce abnormal reproductive or metabolic phenotypes that are transgenerationally transmitted. Human exposures to environmental toxicants have increased due to industrialization and globalization, as well as the incidence of diseases shown to be transgenerationally transmitted in animal models. This new knowledge poses an urgent call to study transgenerational consequences of current human exposures to environmental toxicants.It looks to me like there's an agenda here and Carlos Guerrero-Bosagna is using TED-Ed to promote his personal views.
1. Gene regulation seems to work just fine with transcription factors in those species that don't use DNA methylation and/or histone modification.
HatTip: Jerry Coyne at TED gets epigenetics wrong, but the juggernaut rolls on.