Paleozoic geomagnetism shapes vertebrate evolution

Background. Despite a fifty-year failure of paleontologists to find a viable connection between geomagnetic polarity reversals and evolutionary patterns, recent databases show that the early appearance, radiation, and diversification of Paleozoic vertebrates tend to occur during periods having frequent collapses of the Earth’s geomagnetic field. The transition time during the collapse of the Earth’s protective magnetic shield can last thousands of years, and the effects on biota are unknown. Solar and cosmic radiation, volcanism, weather alteration, low-frequency electromagnetic fields, depletion of ozone, and the stripping of atmospheric oxygen have been proposed as possible causes, but previous studies have found no effects. Methods. Using published databases, we compiled a spreadsheet that shows the first appearance of 1809 age-dated genera with each genus assigned to one of 28 taxonomic groups. From Gradstein’s Geologic Time Scale 2012, we delineated 17 Paleozoic zones with either high or low levels of polarity reversals. Results. From our compilation, we counted 508 Paleozoic vertebrates that first appeared within 20 million-years of the origin of their clade or natural group. These genera represent the initial radiation and diversification of individual Paleozoic vertebrate clades. After compensating for sample-size and external geologic biases, the resulting Pearson’s coefficient between these genera and polarity zones equals 0.781. Using 11 commonly accepted clades and assuming a natural competition existed between them, we counted each genus from a clade’s inception until it was bypassed by a subsequent clade. Here, Pearson's equals 0.901 with a p-value of <0.000001. In a blindfold study, we separated the Paleozoic into a dozen equally-sized temporal bins, then 13 bins, up to 31 bins. The mean Pearson coefficient for these bins is 0.810. After calculating coefficients for four distinct taxonomies, two paleomagnetic systems, three systematics for age-dating within geologic stages, and seven independent spreadsheets, the results suggest a strong relationship exists between Paleozoic vertebrates and polarity reversals. In addition, the earliest species of the major divisions of Paleozoic vertebrates (jawless fish, armored fish, jawed fish, cartilage fish, fish with bones, lobe-finned fish, tetrapods, amphibians, reptiles, and synapsids) first appeared in zones with relatively high levels of polarity reversals. Discussion. The question: is this apparent connection between geomagnetism and the evolution of Paleozoic vertebrate due to environmental or biologic factors. If biologic, why are vertebrates the only biota effected? And after an indeterminate period of time, how do vertebrate families become immune to the ongoing effects of polarity reversals?