How did Herbert Spencer use evolution to explain apparently necessary beliefs?

Herbert Spencer addressed the philosophical problem of "necessary" beliefs—those that appear to be true independent of individual experience—by grounding them in the process of evolution.1

While traditional empiricists struggled to explain how certain beliefs could seem necessary or a priori if all knowledge originates in sensation, Spencer proposed an evolutionary solution. He argued that these beliefs are not innate in the individual in a traditional sense; rather, they are empirical beliefs that have been so consistently confirmed throughout the history of a species that they have become ingrained.1

In this view, what appears to be a necessary truth to a living human is actually the result of inherited, well-attested empirical knowledge passed down from evolutionary ancestors. Through the mechanisms of natural selection and the inheritance of characteristics, these deeply reinforced experiences are transmitted across generations, manifesting in the individual as beliefs that possess the character of necessity.21