Spurious Periods in Terrestrial

We performed a period analysis of terrestrial impact crater ages and epochs of mass extinctions of species, and examined the innuence of the \human{signal" enhanced by the truncation of these data. That truncation distorted the statistics of the rst periodicity detection in the impact crater ages, was checked by repeating this earlier power spectrum method analysis combined with Monte Carlo simulations, and a similar Rayleigh method analysis connrmed this result. Analytical signiicance estimates were then determined with four nonparametric methods to avoid the bias in Monte Carlo sig-niicance estimates. Only integer periods reached a signii-cance of 0.001 or 0.01, and had irregular multimodal phase distributions. We conclude that the data do not reveal significant real periodicity.