From Peter Gay’s brief biography, about the terrible brevity of life in Mozart’s time.
Wolfgang Mozart “was born in Salzburg on January 27, 1756, the seventh and last child of Leopold and Anna Maria Mozart. Of his siblings, five died in infancy, and only one sister, four years his elder, survived … . This appalling balance sheet was only too common in Mozart’s century, even among the prosperous; Edward Gibbon’s father, for one, gave each of his six sons the same first name, Edward, in the expectation—justified, it turned out—that only one of them would carry it to adulthood.”
In Europe and the United State in the eighteenth century, infant mortality rates were over 50%.
The great rise in life expectancy we enjoy (nicely summarized here) occurred as a direct result of the Enlightenment of the 1700s. Current OECD infant mortality rates are less than one-half of one percent.