  The evolution of (non-strange) antibaryon abundances in the hadronic phase of
central heavy-ion collisions is studied within a thermal equilibrium framework,
based on the well-established picture of subsequent chemical and thermal
freezeout. Due to large annihilation cross sections, antiprotons are, a priori,
not expected to comply with this scheme. However, we show that a significant
regeneration of their abundance occurs upon inclusion of the inverse reaction
of multipion fusion, $n_\pi\pi \to p\bar p$ (with $n_\pi$=5-6), necessary to
ensure detailed balance. Especially at SPS energies, the build-up of large
pion-chemical potentials between chemical and thermal freezeout reinforces this
mechanism, rendering the $\bar p/p$ ratio in reasonable agreement with the
observed one (reflecting chemical freezeout). Explicit solutions of the
pertinent rate equation, which account for chemical off-equilibrium effects,
corroborate this explanation.
