The Precambrian

The Precambrian - literally "before the Cambrian" - includes most of the history of life on Earth (albeit very simple life for almost the whole eon). The term is rarely uised now, since modern geology has a more precise undferstanding (down to the geon scale at least, and even life did develop, from prokaryotes during the Archean to eukaryotes during the proterozoic. We have retained the term here in the interest of deep time exponential and logarithmic timescales. So the Precambrian + Phanerozoic is almost ten times longer than the Phanerozoic alone, the Phanerozoic almost ten times longer than the Cenozoic alone, and so on. This unit is also a convenient place to put planetary timescales, since in the case of the moon and Mars all the action was happebning during the early to mid Precambrian, by the late Precambrian these were dead worlds. Only the Earth is unique in this regard, which also ties in with the mutual evolution of life and mineral., MAK120709