| "What findings have made it possible?" Recent evidence is cited, but it's interesting to note that evidence of epigenetic effects (that were ignored as known anomalies) is ancient (of course the mechanism wasn't known.) Such as, the Hinny. "Horses and donkeys are both equids, but their evolution diverged millions of years ago. Still, they are closely enough related that they can interbreed. But the hybrids they produce look different from each other depending on whether the mother is a horse or a donkey. If she is a horse, her baby is a mule and has very long ears. If she is a donkey, her baby is a hinny. Hinnies are rare, but they are generally smaller than mules, with shorter ears. People have known for thousands of years that horse—donkey hybrids differ depending on which species is the mother and which the father. The process thought to be responsible for these differences—genomic imprinting—has been known for only a few decades. Genomic imprinting is an epigenetic mechanism, one of the forms of biological inheritance that operate outside the traditional Mendelian mode. Imprinting is a particularly useful model for investigating epigenetic gene regulation and is a major source of epigenetic regulation in the brain. With genomic imprinting, DNA methylation silences some genes or gene clusters—in egg, sperm, or zygote—depending on which parent they came from. For an imprinted gene, the allele from one parent or the other is shut down and makes no product. The other allele is expressed and produces characteristic outcomes in the offspring. Thus, mom's and dad's chromosomes are not functionally the same. Imprinting is required for normal development, although if the functioning imprinted gene is defective, as sometimes happens, the outcome can also be fatal, or at least debilitating. Some 30 serious disorders are attributed to disrupted imprinting. Some are rare, but more common afflictions, such as cancers and autism, have also been linked to genomic imprinting." https://www.academic.oup.com/bioscience/article/61/8/588/336... Had we cared to investigate this sort of anomaly more closely, I can't help but think that we would have discovered epigenetics decades earlier. I well remember when any such discussion was entirely inadmissable amongst biologists, and proof of one's idiocy if you raised the idea of the genetic mechanism allowing any moderation of DNA as a result of environment or experience (a possibility I did in fact raise in a letter to Jacques Monod in the seventies - only silence came back, such craziness was not worthy of a response.) There's an interesting list of early experiments, some of which may actually have been valid, but were dismissed, here:
https://en.wikipedia.org/wiki/Lamarckism#Weismann's_experime... |