The cosmic star formation rate density (the total mass of stars formed per unit time per unit volume across the universe) exhibits a complex evolution with redshift that does not match Lambda-CDM predictions smoothly. Observations reveal that the star formation rate density peaks at intermediate redshifts (z ~ 2-3) and declines at both higher and lower redshifts, but the detailed shape of this cosmic star formation history, the early decline at very high redshift (z > 6-8), and the low-redshift plateau all present tensions with hierarchical structure formation expectations and galaxy formation models built on cold dark matter (Madau & Dickinson 2014; Bouwens et al. 2016).