Infant mortality

The apparent scale of the celebrations that marked the weaning of a child may reflect the communal joy when a child passed the age of the greatest risk of infant mortality—a risk that would have been considerably higher than in modern industrial societies. Scholars estimate that more than one-third of all infants died during the first few months or years of life, and as many as half of all children did not survive to adulthood. [Footnote: See C. Meyers 1988: 112–13 with reference to ancient Palestinian burials in Jericho, Lachish, and Meiron; in one tomb group, 35% of individuals had died before the age of five; see J. D. Schloen 2001: 122–25; C. Meyers 2005: 16. For Egypt in Late Antiquity, R. S. Bagnall (1993: 182) calculated that ‘nearly one-third of all children died before their first birthday and more than two fifths by the age of five’. According to E. A. R. Willett (2008: 2), “on average, 35 percent of all individuals died before age 5” in Iron Age Cis- and Transjordan.]—Family and Household Religion in Ancient Israel and the Levant, page 294

<idle musing>
That's a frighteningly high number. No wonder they celebrated whenever a baby reached 2-3 years of age.
</idle musing>