Genome complexity: epigenetics in humans shows slim results (Introduction)

by David Turell , Tuesday, February 14, 2023, 18:43 (438 days ago) @ David Turell

Another enormous article which shows epigenetic changes in simple forms do not occur in complex human forms:

https://www.the-scientist.com/features/do-epigenetic-changes-influence-evolution-70591?...

"The idea that epigenetic changes can be inherited across multiple generations in animals only began to crystallize relatively recently, with the first case in C. elegans reported in 2006, for instance. Examples of such phenomena have been reported in mice, too, although some studies have suggested that certain types of epigenetic inheritance might be rare in the rodents. Mammalian cells undergo two rounds of epigenetic reprogramming during gamete production and early embryo development, removing the majority of methylation marks from the DNA and reshaping the histone modification landscape, explains molecular biologist Joan Barau of the Institute of Molecular Biology in Mainz, Germany. He adds that in his view, the evidence so far suggests that mammals lack RNA-dependent RNA polymerases (RdRPs), the enzymes that propagate RNA signals across multiple generations in C. elegans. The difficulty in deciphering the mechanism of transmission of epigenetic marks has made it hard to convince many researchers that such intergenerational processes can occur in mammals, says Alexandra Weyrich of the German Centre for Integrative Biodiversity Research Halle-Jena-Leipzig. “The main problem is that we don’t know yet how [epigenetic changes are] transmitted to the next generation. If we solve that, then [the idea of epigenetic inheritance in mammals would be] more accepted [by] evolutionary biologists and geneticists.” ***

"To some scientists, the fact that cases of transgenerational epigenetic inheritance are often ephemeral—typically lasting only a handful of generations in C. elegans, for instance—argues against a significant evolutionary role. For simple traits controlled by single genetic loci, it would be hard for natural selection to produce a population where all individuals bear the same beneficial phenotype if that trait were unstable and reversed in some lineages, says Brian Charlesworth, an evolutionary geneticist at the University of Edinburgh. “That’s one problem, I think, for believing that this is an important evolutionary process—the apparent lack of stability in many of these cases where it does seem to be well-documented,” Charlesworth says.

"That’s why some scientists see epigenetic inheritance as no more than an adaptation in and of itself—perhaps a kind of bet-hedging strategy to transiently adapt to short-term environmental stressors without committing to stably transmitted, hard-wired changes.

***

"In humans, the evidence is even harder to interpret, with correlational studies so far failing to yield definitive answers about transgenerational epigenetic inheritance, Barau says. “I’m not a total [skeptic] of transgenerational epigenetic inheritance, it’s just that the burden of proof for this is quite high. And it hasn’t been achieved in many of the [claims], especially when you’re talking [about] humans.”

***

"Charlesworth, however, doesn’t see epigenetic inheritance as a challenge to fundamental rules of evolution laid out in the Modern Synthesis. Many documented cases involve subtle traits pertaining to stress responses and fertility, and not lineage-defining evolutionary innovations such as eyes or wings, for instance. In his view, it’s likely that the documented cases of epigenetic inheritance in worms, plants, and mammals are exceptions to the normal rules of heredity, he says. “The evidence from classical genetics, I should say, is pretty strongly against this being anything at all frequent. People have been working on genetics for over 120 years. There’s a huge body of evidence on . . . how [traits are] inherited.”

"Such discussions tap into a broader argument that has long raged over the EES, with frustration on both sides, researchers tell The Scientist. A recent article in The Guardian titled “Do we need a new theory of evolution?” generated rigorous debate among scientists on Twitter. “This all brings very heated discussions [at] the conferences and meetings,” Stajic says via email. “It is definitely very exciting times to be in the field.”

Comment: same result. Studies in simple organisms do not carry over to advanced complex forms. These are natural mechanisms. God, as designer, does not posse these problems, except belief.