Stotz and Griffiths, Biohumanities
environmental influences, it was simply a matter of time before most systems found ways
to manage aspects of their developmental niche. Cytoplasmic chemical gradients,
mRNAs, transcription factors together with the necessary cellular organelles and
structures that are inherited with the ovum, give this process a head start, and maternal
control over the fetus' environment extend to the uterus or pre-hatchling state. Postnatal
factors, such as the licking of pups by rat mothers, continue to influence gene expression
levels. The protein packaging of DNA provides an imprinting system, often called the
histone or chromatin code, which gives parents pre- and postnatal control over the
offspring's gene expression (Meaney, 2004). Parental effects also include differential
provisioning of resources, preference induction (oviposition, imprinting on food, habitat,
and mates), and social learning (Jablonka and Lamb, 2005; Mousseau and Fox, 2003).
There have been repeated attempts to reduce all of these mechanisms of extended
inheritance to the action of inherited or parent-of-origin genes, so that ultimately the real
causes are all genetic. This special pleading fails in the light of the discovery that
development relies not only on the presence of particular genes in an organism but at
least as much on the regulated expression of genomes, which ultimately depends on
environmental, as well as genomic, factors. Wherever there are genes there are
extragenetic factors necessary for their regulated expression.
The sketch just given shows how science criticism can lead to changes in interpretation of
known facts to give rise to a different in this case radically different vision of biology.
One aim of constructing such a new vision is to potentially motivate biologists to