Al
I’ve seen that case-study used to argue for the immaterial nature of mind, which is not an unreasonable line to take. But if we apply it to your scenario, you’re apparently suggesting that the generic human brain that developed suboptimally because it was subject to natural selection was, in the case of this guy, rendered more efficient by gross disease. I can’t quite follow the reasoning of that: in a long medical career I never experienced any diseases that improved human design. Not that I can explain the particular instance.
But you raise a general conundrum. Firstly, in most cases (like the human brain) we have no idea how optimal it is, or isn’t, because we don’t understand even what it does, let alone how its physical structure enables it (eg, does consciousness belong to the brain, or not?). We do know that all of it is used all the time, contrary to the old urban myths that we only use a few percent of it.
Secondly, to both Darwin and Wallace, NS was an optimisation process constantly honing organisms - both used it to account for the perfection they observed in nature. Darwin waxes quite lyrical about it in OoS.
Thirdly, on theoretical grounds NS is now believed to be a bodging tinkerer, incapable for various detailed, but important, reasons like channel capacity of optimisation - ergo, the brain (for example) must be inefficient.
Fourthly, though, there are numerous documented instances of optimisation that can be gauged by information theory (like the near-optimal DNA code itself) or by the laws of physics (such as the efficiency of the compound eye and many others). So in these cases, NS must have managed to excel itself - or else one must say that natural selection wasn’t the only, or even the key, design mechanism in these cases. It’s certainly hard to argue for a process that’s fundamentally incapable of optimisation, except when it achieves it.
Fifthly, from Wallace’s point of view (as we’ve discussed above) mere functionality is not all that is to be observed in nature: he saw an overall pattern. And so apparently sub-optimality at the organismal level, whether due to NS or not, might be observed to optimise things at the ecological level - an inefficient camouflage could optimise predation rates for the ecosyestem as a whole. Or optimisation might occur even at the level of human benefit, for Wallace saw evolution as subsumed in the providential care of mankind. For all his heterodoxy, such a view is pretty close to the Christian doctrine of creation - John Walton says the central theme of creation is cosmic function (not organismal efficiency), and the Genesis creation account is undeniably deeply anthropocentric.
With all those considerations in mind, one needs to define pretty closely on what basis one can say that the human brain is “suboptimally wired by natural selection”. Is it verifiable, or just hypothesis piled on hypothesis? Ie, “We believe NS to be the main biological agent of design; we believe NS on theoretical grounds to be incapable of optimisation; ergo we deduce that the unfathomable human brain is probably jerry-built and speculate that some non-existent process could improve it.”