  For many organisms, the number of sensory neurons is largely determined
during development, before strong environmental cues are present. This is
despite the fact that environments can fluctuate drastically both from
generation to generation and within an organism's lifetime. How can organisms
get by by hard-coding the number of sensory neurons? We approach this question
using rate-distortion theory. A combination of simulation and theory suggests
that when environments are large, the rate-distortion function---a proxy for
material costs, timing delays, and energy requirements---depends only on
coarse-grained environmental statistics that are expected to change on
evolutionary, rather than ontogenetic, timescales.
