We know that this threshold exists, because we don't get age-related diseases until we're in middle age, even though the damage has been accumulating since before we were born.
Kita tahu takat ini wujud, sebab kita tidak mendapat penyakit berkaitan lanjutan usia sehingga kita dalam usia pertengahan, walaupun kerosakan telah mula menimbun semenjak sebelum kita lahir.