>"Phylogenetic trees of life typically reveal that the extant
>hyperthermophilic bacteria and archaeal species, which inhabit environments
>of extreme temeperatures, have some of the deepest and oldest branches, and
>it is consequently a widely endorsed textbook view that the common ancestor
>of life was adapted to hot conditions.
> "The proportion of all nucleotides that are either guanine or cytosine (the
>G+C content) of ribosomal RNA is a reliable indicator of the environmental
>temperature of an organism, so an estimate of the G+C content of the root of
>the tree of life provides evidence for the environmental conditions that
>prevailed when the common ancestor to life arose." Mark Pagel, "Inferring
>the Historical Patterns of Biological Evolution," Nature, 401(1999):877-884,
>p.879
Some of these results have been questioned as possibly artifacts of the
analytical techniques. There does not appear to be a consensus.
David C.
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