Embedded Substrate Theory predicts that systems in transition leave remnants of previous systems running inside new ones. This paper applies that framework to infectious and immunological epidemiology: elderly individuals carrying accumulated microbial, viral, and immunological substrate from earlier decades co-habit with young children whose immune systems are in active development. This paper proposes that multigenerational co-habitation constitutes a substrate transfer vector — transmitting legacy microbial and immunological architecture from one generation's developmental environment into another's. Japan's documented 1.7x increase in food allergies across all age groups simultaneously from 2010-2019, coinciding with sustained high multigenerational co-habitation rates, is proposed as a natural controlled experiment. High-income East Asian countries with high elderly co-habitation show divergent disease profiles from equivalent-income Western countries with lower co-habitation rates. Epidemiological study with co-habitation density as explicit independent variable is proposed.
Budinny V (Fri,) studied this question.