1Integral projection models (IPMs) are extremely flexible tools for ecological and evolutionary infer-2 ence. IPMs track the distribution of phenotype in populations through time, using functions describing 3 phenotype-dependent development, inheritance, survival and fecundity. For evolutionary inference, two 4 important features of any model are the ability to (i) characterize relationships among traits (including 5 values of the same traits across ages) within individuals, and (ii) characterize similarity between indi-6 viduals and their descendants. In IPM analyses, the former depends on regressions of observed trait 7 values at each age on values at the previous age (development functions), and the latter on regressions 8of o↵spring values at birth on parent values as adults (inheritance functions). We show analytically that 9 development functions, characterized this way, will typically underestimate covariances of trait values 10 across ages, due to compounding of regression to the mean across projection steps. Similarly, we show 11 that inheritance, characterized this way, is inconsistent with a modern understanding of inheritance, and 12 underestimates the degree to which relatives are phenotypically similar. Additionally, we show that the 13 use of a constant biometric inheritance function, particularly with a constant intercept, is incompati-14 ble with evolution. Consequently, current implementations of IPMs will predict little or no phenotypic 15 evolution, purely as artifacts of their construction. We present alternative approaches to constructing 16 development and inheritance functions, based on a quantitative genetic approach, and show analytically 17 and through an empirical example on a population of bighorn sheep how they can potentially recover 18 patterns that are critical to evolutionary inference. 19 20 Keywords: integral projection models, regression to the mean, inheritance, development, body size, 21 evolutionary responses, bighorn sheep 22