If we talk about post human we think of far advanced AIs or Cyborgs, but arent we, per definition, allready beyond the "natural" limits of being human?
If we see natural as all things which do not equal culture, then we for sure are far beyond that.
Communication, health(lifespan), strenght, society, the adaption of our bodies do not resemble that much the life of that what we have been without technology (some 40.000+ years in the past).
Or do we only consider something as posthuman if it isnt that concerned with the basic questions of the "human condition" (meaning of life, mortality, pain, origin of the universe,...)?