The "human" Statistics of Terrestrial Impact Cratering Rate

. The most significant periodicities in the terrestrial impact crater record are due to the "human--signal": the bias of assigning integer values for the crater ages. This bias seems to have eluded the proponents and opponents of real periodicity in the occurrence of these events, as well as the theorists searching for an extraterrestrial explanation for such periodicity. The "human--signal" should be seriously considered by scientists in astronomy, geology and paleontology when searching for a connection between terrestrial major comet or asteroid impacts and mass extinctions of species. Key words: Solar system: Earth -- Comets, Techniques: statistical, Galaxy: solar neighbourhood 1. Introduction An outstanding series of papers appeared in 1984 when a 28.4 Myr cycle was detected in the terrestrial impact crater record (Alvarez & Muller 1984, Davis et al. 1984, Whitmire & Jackson 1984). This value was close to the 26 Myr cycle discovered in the geological record of major mass extinct..