The way organisms are built is weird
Engineers routinely borrow ideas from biology. We have swimsuits like sharkskin and sticky-tape like gecko feet. But our borrowing is confined to the way things work, not how they are built. We copy the structure of a gecko’s foot, but not how that structure develops in a gecko embryo. This is because the way organisms are built is very strange.
Human construction is top-down: it starts with prefabricated parts, a plan, and someone to carry it out. A trip to IKEA captures these elements. Building that new set of drawers requires (a) a flat-pack of parts, (b) a fold-out manual, and (c) you.
The construction of an organism, in contrast, looks nothing like this. There are no obvious instructions, no prefabricated parts, and no visible assembler. The creature just builds itself from the bottom up.
Consider how remarkable this process is
From a single cell and a suitable environment, a functioning organism emerges — with limbs, organs, and attitude. How does such complex order unfold from one tiny cell?
This method of construction is capable of producing a broad range of outcomes. Start with a different cell and you get a different, species-typical arrangement — fins, not wings; scales, not feathers. What guides the process to such diverse, specific outcomes?
Despite this diversity, some unifying process underlies how organisms construct themselves. A chick and a fish are very different. Yet they are connected by a continuous series of small, viable changes. How can such a complex process be modified gradually?
How do explain these features?
Despite the weird way organisms are built, we often treat them like products of human engineering. DNA is cast as the plan, or a blueprint, or instructions for building the organism. Then we have a neat explanation for the features above:
The DNA inside that first cell contains a tiny plan for building the organism. This plan specifies how the organism is built. Different plans lead to different organisms. Gradually modifying the plan allows a smooth transition between them.
There is (rightly) a good deal of criticism of such neat explanations. Many biologists and philosophers have argued that these engineering analogies are deeply misleading, and focused overly much on DNA. Instead, we need to look elsewhere: on the power of self-organisation, and the reciprocity of interaction between the organism and its environment.
But that is not our only option. We can continue to draw on engineering ideas, rethinking and clarifying the role DNA might play in light of construction that proceeds from the bottom up. This website presents a series of models that explore the idea that DNA is a bottom-up control system that evolves to exploit the environment and self-organisation. I show how this view can help explain the features above, and can shed light on seemingly contrary ideas, such as environmental plasticity, self-organisation, and goal-directed behaviour.