Yeah, no. Look up "sick sinus syndrome" and "premature ventricular complex". (The latter occurs in up to 75 percent of people at times.)

4B years, yes, but evolution is a pile of kludges on top of kludges.

The most pervasive misunderstanding about evolution is that it leads to "perfection". Sure it is a kind of optimization procedure, but a) it's optimizing on a loss function that is measured on the population scale, not the scale of a particular organ, so don't expect your pet figure of merit to be optimized even in an average sense, and certainly not in an individual; and b) there is not a unique optimum, the optima are not stationary, and local optima generally are not all that sharp, so do not expect the population to be all that close to the optimum either.