“There is an important distinction between a blueprint and a recipe. A blueprint is a detailed, point-for-point specification of some end product like a house or a car. One diagnostic feature of a blueprint is that it is reversible. Give an engineer a car and he can reconstruct its blueprint. But offer to a chef a rival’s pièce de résistance to taste and he will fail to reconstruct the recipe. There is a one-to-one mapping between components of a blueprint and components of the end product. This bit of the car corresponds to this bit of the blueprint. There is no such one to one mapping in the case of a recipe. You can’t isolate a particular blob of souffle and seek one word of the recipe that ‘determines’ that blob. All the words of the recipe, taken together with all the ingredients ,combine to form the whole souffle. Genes, in different aspects of their behaviour, are sometimes like blueprints and sometimes like recipes.”
From A Devil’s Chaplain, Richard Dawkins
This quotation leapt out at me because I can still remember the moment, years ago, when I really realized how dynamic human beings were. I was reading something in biology or genetics, and before I’d understood genes kind of like Lego blocks: this gene makes that part of you, that gene makes that part of you. But I realized suddenly that the genes were just chemical components, and that they could react with the chemistry of their environment — so two identical eggs might develop slightly differently if they were given to two different mothers, because the mothers’ chemistry would be different. They would release different kinds and different levels of hormones depending on their own genes, and their diet (among other things). And when we became adults, I realized further, we were still continuing to be made, our brains constantly reforming based on experience. That was before I started reading about the life of microbacteria inside us, and how they are engaged in constant love and war with “our” cells, and how these colonies can change drastically depending on what are eating.