I think there is strongest support for a hot earth at the
origin of life.
1. Heavy volcanic activity would "bring chemical compounds
to the surface that would otherwise not be found."
2. The hotter it is (up to the end of liquid water at 100C)
the faster the chemical reactions.
3. The hotter, the faster the change and the quicker the
origin would be and with zircons formed at 4.1-4.2 and
life perhaps pushed back to 3.8 (West Greenland) there is
little room left for life. Also this period seems hot. An
origin in lower temp. would take too long and be too slow
to fit the evidence.
4. the Tm of both DNA and RNA is very high "what conditions
would require this resistance?'
5. "The total volume of the oceans ... passes through the
hot basalt rock every eight million years." thus
sterilizing the ocean. That suggests that there was not
unlimited time for life to begin
6. "the luminosity of the Sun presumably was only three
quarters of what it is today, but the greenhouse effect
of the CO2 rich atmosphere must have overcompensated for
this difference." Also methane and even water vapor have
greenhouse effect. Plus the hot earth was radiating heat.
7. "meteorite impacts must have heated most of the seawater
to boiling and saturated the atmosphere with dust for
millenia."
and these quotes
"Both researchers (Wachtershauser, Stetter) agree in
thinking that the origin of life happened in a rather hot
environment. As I will explain, certain features of the
family tree of life support this... The observation that
hyperthermophilic adaptation is particularly widespread
among archaebacteria led some researchers to believe that
adaptation to extreme conditions is not a feature acquired
during the course of evolution, but one that most of today's
organisms have lost in the course of an evolution away from
hyperthermophilic ancestors
Evidence for this... comes not ony from the archae bacterial
domain. If one screens the entire tree of life for
thermophiles, one tends to find them in the deepest
branches" (though as the author points out this only takes
us back to the last commmon ancestor)
Quotes from Life on The Edge, M. Gross.
If true then prebiotic life was those chemicals and that
chemical system which survived this hot environment - and
through that heat cycle was forced into novel variants that
allowed it to continue and to continue to improve its
ability to adapt to that environment.