For me it took over 1 year of daily "chiropractic yoga" to repair posture to be able to do it. Look up esther gokhale lectures on youtube, she describes well how in the ~1900 the "J" spine was considered normal, but in the following 50 years at some point it had transformed to the current chronicly diseased "S" spine being considered normal.I just tried, thanks for the explanation, but no I can not touch every vertebre at the same time, I wonder if there are people capable of doing this kind.
While it might have become "normal" as in what most people have, it is not "healthy" or "desirable"