It seems probable that humans have been on the planet, with much the same brain, for about 250,000 years.

If you want to understand the nature of something, to find out the truth, that is one thing. If you want to play semantics, make up wild thought 'experiments', that is another thing. I am not so interested in the latter, though I do appreciate that it can be fun, however unproductive.

Early studies of sleep and dreaming were crucially dependent on waking subjects up during sleep to find out whether they are dreaming or not. Using that strategy, it was found that when the eyes are rapidly moving (REM sleep) people are usually dreaming; when the eyes are not moving, there may be some mentation, but little in the way of visually rich dreams.

Many mammals and birds have systems for strong self-control, and it is not difficult to see why such systems were advantageous and were selected for. Biding your time, deferring gratification, staying still, foregoing sex for safety, and so forth, is essential in getting food, in surviving, and in successful reproduction.

Many philosophers in the second half of the 20th century really seemed to think that they were laying the foundations for science by laying down the conceptual (necessary) truths.

It is surely important that the differences between coma, deep sleep, being under anesthesia, on the one hand, and being alert on the other, all involve changes in the brain.

It is important to understand that while oxytocin may be the hub of the evolution of the social brain in mammals, it is part of a very complex system. Part of what it does is act in opposition to stress hormones, and in that sense release of oxytocin feels good - as stress hormones and anxiety do not feel good.