ReviewEVOLUTIONARY BIOLOGY

The timetable of evolution

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Science Advances  17 May 2017:
Vol. 3, no. 5, e1603076
DOI: 10.1126/sciadv.1603076

Figures

  • Fig. 1 The evolutionary timetable, showing the course of evolution as inferred from fossils, environmental proxies, and high-resolution geochronology.

    Phanero, Phanerozoic; Prot, Proterozoic; Ceno, Cenozoic; E, Ediacaran; Cam, Cambrian; O, Ordovician; S, Silurian; D, Devonian; Car, Carboniferous; Per, Permian; Tr, Triassic; J, Jurassic; K, Cretaceous; Pal, Paleogene; Neo, Neogene. Crosses indicate times of major mass extinctions.

  • Fig. 2 The geologic history of Fe in seawater and O2 in the atmosphere and surface ocean.

    Fossil images from left to right show biogenic stromatolites, accreted by microbial mat communities (2700 Ma; Fortescue Group, Australia), an early eukaryotic microorganism (1400 to 1500 Ma; Roper Group, Australia), and an Ediacaran metazoan (543 Ma; Nama Group, Namibia). PAL, present atmospheric level.

    [Photo credits: All photos by Andrew H. Knoll.]
  • Fig. 3 The regeneration process.

    Gene duplication (A) or recombination (B) generates a starting condition for the search process, at rate w. (C) From the starting condition, we require k mutational steps, each at rate u, to reach the target sequence, which encodes a new function. At each step, there is the possibility to receive inactivating mutations, at rate v, which destroy the search. The frequency of the wild type is denoted by x0. The frequencies of the intermediate steps in the search process are denoted by xi. At steady state and assuming neutrality, we have the following frequencies: Embedded Image and Embedded Image. Let us consider a numerical example: w = 10−7, u = 10−9, v = 10−7 per cell division. Then, cells that have made as many as 10 steps toward the target have a frequency of about 5 × 10−19 and are present on a planetary scale with a total cell number of the order on 1030.

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