You do not currently have permission to view the full text for this document. Please sign in to an account with an active subscription or contact support.
Dr. Merchant has generously provided a thought-provoking answer to my papers, and reinforces the truism that all development is a combination of gene and environment co-action. Generally speaking, it is true that genomes cannot do anything without an environment to interact with. However, if we stop at that point and look no further into specific examples, it is easy to miss the nuances that I tried to highlight in my essay, which is only to say that in some cases, the phrase ‘gene-environment co-action’ can be misleading because one is far more active in the process than the other, and all too often such generic statements tend to gloss over just how important the genome can be in those cases. Making a statue of Zeus, to use an analogy, can be described as ‘sculptor and stone lump co-action’, but it might mislead one into thinking that the lump has just as much agency as the sculptor does. I will try to clarify my concerns here, but in general I find much to agree with in Merchant's analysis.
In the case of the lac operon, we saw how the E. Coli genome makes proteins that test for the presence of lactose and glucose and then acts accordingly when those testing proteins turn on or off whatever metabolizing proteins are needed. Yes, this behaviour requires environmental ‘input’ (lactose, glucose, some kind of medium), but it's hard to understand in what way the lactose is ‘acting’ here other than just passively being what the genome is specifically looking for. In this case the genome is setting the stage and calling all the shots: it determines what is looked for and what to do with it, in order to accomplish its functional goals.
In the case of BDNF (the gene that codes for ‘brain derived neurotrophic factor’, a hormone, the presence or absence of which affects a large array of very complex cognitive and behavioural events, starting with neural proliferation in utero to a variety of neural processes throughout the lifetime [reviewed in Rothman & Mattson 2012]), we ha