In an item in the January 2006 issue of Physics Today (page 32), Jim Dawson quoted National Academy of Sciences president Ralph J. Cicerone on “ ‘controversies’ (e.g. the Cambrian explosion) that evolutionary scientists have refuted many times using the available evidence.” I thought Physics Today readers might like to know what some of the refutations are. How privileged we are today to know with more certainty than did Charles Darwin himself!
A true follower of Darwin knows that “the sudden appearance of animal fossils at the beginning of the Cambrian [period] was of particular concern to him.” 1 Darwin argued that the animals should have diverged gradually during a long prior period—“as long as, or probably far longer than, the whole interval from the Silurian [that is, the Cambrian period] to the present day.” 2 Because the required fossils were not found, he confessed, “The case at present must remain inexplicable; and may be truly urged as a valid argument against the views here entertained.” 3
Only in 1954 were very early pre-Cambrian fossils convincingly found: bacteria and one-celled fungi, abundantly frozen in 2-billion-year-old black chert from North America. 4 This discovery quadrupled the known age of life on Earth. An investigative explosion into pre-Cambrian paleobiology was then inevitable. Since the 1960s, fossilized microbes up to 4 billion years old have been found in some of the oldest rocks on Earth.
We do not know the whole answer to Darwin’s concern, regarding the sudden appearance of animal fossils, with developed body plans in all the phyla. Nevertheless, that living things (at least one-celled microbes) flourished long before the Cambrian, just as claimed, is today indisputable.
