Implications of recent advances in the understanding of heritability for neo-Darwinian orthodoxy

It has long been accepted that natural selection acts on variation produced as a result of random mutation. However, the origins of this variation and the factors that determine whether it can be passed onto the next generation have never been thoroughly studied. Distorted inheritance of mutation can be seen in the case of low dose, chronic exposure of rats to the anticancer drug cyclophosphamide. This may have parallels in fathers who smoke prior to conception of their children, who are at a small but significantly increased risk of blood cancers. Non-genomic inheritance of variation can be seen with paramutation or the silencing of one allele by another, even when it is not present in the individual. It has also been alleged for DNA methylation, in women with diabetes or hypertension whose children then acquire the diseases. However, in this case the children acquire the disease in utero as a result of the same dietary factors that are affecting the mother. Most recently, it has been found that the binding of certain proteins at specific sites in sperm DNA appears to mark those regions for early expression in the embryo. Alterations in the pattern could compromise fertility and perhaps lead to reproductive isolation and hence to enhanced rates of evolution. It is proposed that these non-random and epigenetic influences on heritable mutation should be integrated into a modernised neoDarwinism.