David Campbell writes, "Even when the situation exists first, the mutation
itself is not regarded as a response to the situation but rather something
that happens and is successful relative to the previous condition in contact
with the same
situation." Let me apply this scenario to the increase in brain size
example: The _situation_ is the need to survive (function). A mutation just
happens for increase in brain size.
Its phenotype of slightly increased brain size (form) is selected because it
increases chances of survival. Need for survival is the engine that drives
increase in brain size.
Or did brain increase dramatically in size, driven by intrinsic factors
(form), thus making possible the struggle to survive (function)? This is the
position design theorists would take.