Corollary discharge is an interesting mechanism, and helps explain several areas of the nervous system. It makes sense of the phenomena of phantom limbs, and also helps explain several types of motion sickness. The mismatching signals that the brain receives from corrolary discharge and input create the pain and the sickness. But it seems odd that the body has a mechanism that causes unreasonable pain or sickness. The important point with the symptoms of motion sickness and photntom limbs is that both of these situations are not normal, or expected to the body. So they represent a malfunction in a normally smooth running information collection and comparision process. These symptoms can be examined, and through them, you can see how the nervous system normally works.
The motion sickness problem is recent problem, that has only been encountered by modern societies. It is a reminder that while we may become more advanced in our technology, we cannot go beyond the limits of what we were originally adapted for. Originally, people just propelled themselves. So all of our nervous mechanisms are for walking or moving oursleves, and coordinating our movement. But with the advent of technology, we have begun to be moved by things other than ourselves. This causes confusion for our nervous systems. Also, we are spcifically adapted to the gravitational pull on earth. So when astronauts go into outer space where the gravitational pull is different, they also become sick. Small conflicts like this remind us that we are only human, and that there are limits to what we can technologically do.
Very much agree with your point, an important and subtle one, that our culture puts us in situations which are novel in terms of evolution and hence we may not have the responses appropriate for it. What's additionally interesting though is that "feeling sick" motivates us to find equally novel ways to deal with the novel circumstances. So maybe we can both be "only human" and have some hope, at any given time, of being more than that (or at least more than what that means at any given time)? PG