# Revisiting the Biological Ramifications of Variations in Earth's Magnetic Field

## TL;DR

This paper reviews how changes in Earth's magnetic field, including growth and reversals, likely had minimal impact on biological radiation exposure and atmospheric escape, challenging some hypotheses about their role in major biological events.

## Contribution

It synthesizes recent paleomagnetic evidence and models to assess the biological and atmospheric effects of Earth's magnetic field variations, providing new insights into their significance.

## Key findings

- Radiation dose rates and atmospheric escape rates vary by less than a factor of two.
- Magnetic field variations are unlikely to explain Cambrian radiation or mass extinctions.
- Implications for early Mars and exoplanets around M-dwarfs are briefly discussed.

## Abstract

An Earth-like planetary magnetic field has been widely invoked as a requirement for habitability as it purportedly mitigates the fluxes of ionizing radiation reaching the surface and the escape of neutrals and ions from the atmosphere. Recent paleomagnetic evidence indicates that the nucleation of Earth's inner core, followed perhaps by an increase in geomagnetic field strength, might have occurred close to the Ediacaran period. Motivated by this putative discovery, we explore the ensuing ramifications from the growth or reversals of Earth's dynamo. By reviewing and synthesizing emerging quantitative models, it is proposed that neither the biological radiation dose rates nor the atmospheric escape rates would vary by more than a factor of $\sim 2$ under these circumstances. Hence, we suggest that hypotheses seeking to explain the Cambrian radiation or mass extinctions via changes in Earth's magnetic field intensity are potentially unlikely. We also briefly discuss how variations in the planetary magnetic field may have impacted early Mars and could influence exoplanets orbiting M-dwarfs.