No, actually that isn't true. Until the mid-twenties/early thirties a human produces more new cells than he loses in dead cells. Biological organisms are not rocks which continually break down; they self repair, increase in size and reproduce.
On a population basis, which is what evolution is all about, each new generation brings a renewal.
Renewal is not change. each generation does not bring change. If it does on a minuscule basis how many billions of years did it take for man to evolve to what we are today?