2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/196496Higher-dimensional theories have the remarkable feature of predicting a time (and hence redshift) dependence of the `fundamental' four dimensional constants on cosmological timescales. In this paper we update the bounds on a possible variation of the fine structure constant alpha at the time of BBN (z =10^10) and CMB (z=10^3). Using the recently-released high-resolution CMB anisotropy data and the latest estimates of primordial abundances of 4He and D, we do not find evidence for a varying alpha at more than one-sigma level at either epoch.5 pages, 1 figure, minor misprints corrected, references added. The analysis has been updated using new BOOMERanG and DASI data on CMB anisotropyAstrophysicsHigh Energy Physics - PhenomenologyHigh Energy Physics - Theorytext