Stotz and Griffiths, Biohumanities
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external environment. Therefore, alleged explanatory categories such as `genetic' versus
`environmental', instead of explaining the origin of a phenotype, preclude further
investigation into its real causes.
The concept of a genetic trait, and the related idea of innateness, are often defended by
pointing to the allegedly unique role of DNA in heredity. Transgenerational stability of
form, however, requires more than faithful transmission of DNA. Genome sequences
depend on the context for their differential expression. Natural selection selects adaptive
phenotypes, which are always derived from non-linear interactions among a range of
diverse developmental resources. Their organization frequently exhibits phenotypic
plasticity, a capacity that allows the organism to react adaptively to different
environmental conditions (Pigliucci, 2001; West-Eberhard, 2003). The stable but
sufficiently plastic inheritance of an adaptive developmental system results from the
reliable transmission of all the necessary developmental factors across generations. In
other words, heredity relies on a stable `developmental niche' which is faithfully
reconstructed by various combinations of the population, the parent and the organism
itself. The unit of evolution is the whole developmental system (Schlichting and
Pigliucci, 1998; Waddington, 1952).
To understand heredity and development we should "Ask not what's inside the genes you
inherited, but what your genes are inside of" (West and King, 1987, 552). What counts is
not only the particular gene you inherit but also when, where and how it is expressed by a
time- and tissue dependent regulatory network. Given the vulnerability of the genome to