You might recall from high school biology a scientist by the name of Jean-Baptiste Lamarck. He proposed a mechanism of evolution in which organisms pass on traits acquired during their lifetimes to their offspring. The textbook example is a proposed mechanism of giraffe evolution: If a giraffe stretches its neck to reach higher leaves on a tree, the giraffe would pass on a slightly longer neck to its offspring.
Ever since news broke of a scientific study that appeared to show that mice may inherit an acquired fear of smell from their parents, and the scramble to identify by what mechanism it might be happening, I’ve been following this debate on epigenetic inheritance and whether this revives Lamarckian evolution.
In this article, Berezow looks at a review paper that reaches a skeptical conclusion.
However, Heard & Martienssen are not convinced. In their Cell review, they admit that epigenetic inheritance has been demonstrated in plants and worms. But, mammals are completely different beasts, so to speak. Mammals go through two rounds of epigenetic “reprogramming” — once after fertilization and again during the formation of gametes (sex cells) — in which most of the chemical tags are wiped clean.
They insist that characteristics many researchers assume to be the result of epigenetic inheritance are actually caused by something else. The authors list four possibilities: Undetected mutations in the letters of the DNA sequence, behavioral changes (which themselves can trigger epigenetic tags), alterations in the microbiome, or transmission of metabolites from one generation to the next. The authors claim that most epigenetic research, particularly when it involves human health, fails to eliminate these possibilities.
It seems to me that the argument about whether or not this inheritance happens through epigenetics is beside the point. The main question is whether or not acquired traits can be inherited. If it comes down to “behavioral changes” (which the mice study claimed to have eliminated), “alterations in the microbiome”, or “transmission of metabolites” then the answer would seem to be yes, albeit to a far less extent than anything Lamarck probably imagined.
Of course, if the answer is undetected (and entirely coincidental) mutations, then the existing paradigm would hold.