Geological stratigraphy,together with radioactivedating, show the sequence of events inthe history of the Earth.Note the entry for “cyanobacteria” and “stromatolites” only onebillion years after the formation of the Earth.How did life arise so quicklyafter the end of the HadeanPeriod?
A New Picture of the Early EarthLeft, Bruce Watson; right, Don DixonAGES AGO Analyses of crystals in rocks in Australia, left, have formed a new picture of the early Earth, depicted with youngoceans in the painting at right.New York Times, Tuesday, December 2, 2008Isotope composition of ancient zircons suggests that Earth was cooler andwetter in the Hadean Period, giving more time for prebiotic evolution.
If the minimal requirements for life are catalysis and heredity (Can weenvision life without reproduction? Can we envision reproduction withoutcatalysis and heredity?), what are the most basic molecules that satisfy theminimal requirements?If they are proteins and DNA, how are the two connected? Is there analternative?How did the genetic code evolve?How are genomes organized? Do they evolve for efficiency?