Governments should reduce prices before rationing care.

I welcome the Comment by Didier Raoult (Jan 9, p 104), which proposes the post-Darwinist concept of the evolutionary pathway as a rhizome instead of a tree, with inheritance occurring not only vertically but also laterally. He rightly addresses how the genomic revolution has forced us to reconsider the way we describe evolution. Perhaps one of the most important unresolved issues in the study of species evolution is the adaptation to a changing environment, bringing all the evolutionary changes seen in a short period. Epigenetics could explain this phenomenon in eukaryotic species including human beings. Most epigenetic changes occur within the course of one individual organism’s lifetime, but, in recent investigations, epigenetic changes were found to be inherited from one generation to the next: the inheritance of acquired characteristics of Lamarck. Of course, Lamarckism’s examples of giraffes stretching their necks to reach leaves high in trees, gradually lengthening their necks, and then having offspring with slightly longer necks only shows that generational change is not a simple thing. However, it has been shown that the epigenetic marks by DNA methylation can be inherited across multiple generations in mice, implying that not only prenatal maternal but also grandmaternal exposures to methyl donors may influence subsequent gene expression in the offspring. I propose that our current understanding of epigenetics could partly reinstate Lamarck in the light of a post-Darwinist model of evolution.