  Spacetime variations of physical constants can be associated with the
existence of Higgs-like scalar field(s) that couple non-universally to the
baryonic matter. Recent results of astronomical spectral measurements of the
fractional changes in the electron-to-proton mass ratio, mu = m_e/m_p, at low
(z ~ 0) and high (z ~ 6.5) redshifts are discussed. It is shown that the
distribution of the most accurate estimates of Delta mu/mu = (mu_obs -
mu_lab)/mu_lab ranging between z = 0 and z ~ 1100 can be approximated by a
power low Delta mu/mu = k_mu (1+z)^p, with k_mu = (1.7 +/- 0.3)x10^-8 and p =
1.99 +/- 0.03, implying a dynamical nature of the scalar field(s).
