The Extended Habitable Epoch of the Universe for Liquids Other than
  Water
  At high redshifts, the temperature of the cosmic microwave background (CMB)
was higher than its value today. We explore the possibility that life may have
arisen early because the higher CMB temperature would have supplied the
requisite energy for the existence of different solvents on the surfaces of
objects. At redshifts of $z \lesssim 70$, after the first stars are predicted
to have formed, a number of molecules (but not water) might have existed in
liquid form over intervals of $\sim 10$ Myr to $\sim 100$ Myr. We delineate the
challenges and prospects for life in the high-redshift Universe, and assess the
various candidates for alternative biochemistries in this context -- of the
options considered herein, we conclude that ethane is probably the most
promising contender.
