ðə pɹˈaɪmɚɹi fˈæktɚ pɹəmˈoʊɾɪŋ stˌændɚdᵻzˈeɪʃən ʌvðə lˈaɪf kˈoːɹs wʌz ɪmpɹˈuːvmənt ɪn mɔːɹtˈælᵻɾi ɹˈeɪts bɹˈɔːt ɐbˌaʊt baɪ ðə mˈænɪdʒmənt ʌv kəntˈeɪdʒəs ænd ɪnfˈɛkʃəs dɪzˈiːzᵻz sˈʌtʃ ɐz smˈɔːlpɑːks.
The primary factor promoting standardization of the life course was improvement in mortality rates brought about by the management of contagious and infectious diseases such as smallpox.