I seem to disagree with this statement. While the human anatomy is an extremely complex organism, just because something can't be explained, doesn't mean that it isn't inherently rational.

I'm not suggesting that everything is 1 to 1 in terms of reaction = function, however there should be some sort of order and flow within our body, if not for basic function.

If you look at something like diet and exercise, the body is extremely versatile with what it can do with the foods we eat, regardless of quality, yet the end outcome is very similar. We grow at a certain age and we usually die at a certain age, of course with different extremes on both ends.

Of course, these are all just arguments. Philosophy transcends rationality.