To answer: how can evolutionary understanding inform philosophy? Here I will give a concrete example: the nature of language. If we take language from the form in which we find it as fully developed, then all things are possible; it is too close for us to see clearly. Yet by returning to examine its ontogenesis, both in terms of evolutionary and developmental terms, we can see the seed; that essential nature which remains present today. For the latter, the studies of Piaget, whatever one thinks of his specific claims, are an invaluable resource. I apply the same principled viewpoint to development at the level of the species and individual: all proceeds by the parsimonious dialectic of exaptation and selection. Now, the question becomes: how do we get from the simplest organisms—a bacteria, for example—to human language?
We may begin with categorisation: any organism must categorise to survive. Moving towards resources, for instance, and away from threats. Yet for the bacteria it is quite obvious, if we forget for humans, that these categories may well be mistaken. Those that are mistaken will not survive. Nature selects for accurate categorisation. Of course, it selects only for efficient categorisation in relation to a given environment; if a new threat is introduced, then prior work will be insufficient.
What may help here, however, would be the capacity to generalise associations. We have learnt that something is a threat, then when we come across something new, we regard this as a threat also. The precise degree of generalisation will be subject to the tension of variation and selection. We may ignore a plentiful resource out of negative associations with something similar. Those that are less discerning may thrive by accessing an untapped resource.
A third step is possible here, that we may learn by observing others. We notice that another is consuming something which we deem poisonous, yet they are fine. This may lead us to imitate them, thus refining our categories by a new mode of learning. Similarly, we may see an organism eating something; it would be better to avoid that if soon after they died. Here we might see in this latter sense a progenitor of what we think of superstition—better safe than sorry, as they say.
Now, even better would be if we could somehow communicate this. Perhaps we point to some berries, then by our gestures express sickness or death. This capacity to communicate basic categorisations—threat, resource, towards, away—would itself prove advantageous. Significantly, here we find that pointing and gestures are the natural first forms. At this point, we can readily imagine the progress through to sign language—then on to spoken language, written, etc. All this by the same process of variation and selection (i.e., exaptation) as produced the eye from an initial cluster of light-sensitive cells.
But then, what does this tell us? If we see language in terms of its primordial form, we can thereby better understand its limits. I do not claim here to have given anything like an exhaustive account; indeed, I am far from understanding the ontogenesis of language! Yet we can place basic limits and sketch outlines. These can then inform—or perhaps more so, constrain—further philosophical enquiry.