  A larger Planck scale during an early epoch leads to a smaller Hubble rate,
which is the measure for efficiency of primordial processes. The resulting
slower cosmic tempo can accommodate alternative cosmological histories. We
consider this possibility in the context of extra dimensional theories, which
can provide a natural setting for the scenario. If the fundamental scale of the
theory is not too far above the weak scale, to alleviate the ``hierarchy
problem," cosmological constraints imply that thermal relic dark matter would
be at the GeV scale, which may be disfavored by cosmic microwave background
measurements. Such dark matter becomes viable again in our proposal, due to
smaller requisite annihilation cross section, further motivating ongoing low
energy accelerator-based searches. Quantum gravity signatures associated with
the extra dimensional setting can be probed at high energy colliders -- up to
$\sim 13$ TeV at the LHC or $\sim 100$ TeV at FCC-hh. Searches for missing
energy signals of dark sector states, with masses $\gtrsim 10$ GeV, can be
pursued at a future circular lepton collider.
