Earth’s magnetic field and the evolution of life

The history of Earth’s magnetic field can provide insight into how life evolved, an area Jean-Pierre Valet studied in his insightful suggestion of a relationship between the Laschamp excursion and Neanderthal extinction. Here, I will discuss how recent findings show potential linkages on longer time scales between magnetism and the origin of life, animal evolution and habitability.  The study of magnetism held by minute magnetic inclusions in zircons indicates that the geomagnetic field is at least 4200 million years old, which corresponds in time with genetic estimates for the age of the last universal common ancestor. The early establishment of the field would have provided shielding from solar and cosmic radiation, broadening the potential environments where life might have originated. At the end of the Precambrian, at ca. 591 to 565 million years ago, the magnetic field nearly collapsed, but growth of the inner core during earliest Cambrian times renewed the magnetic field and shielding, helping to prevent drying of the planet. Before this renewal, the ultra-weak magnetic shielding may have had an unexpected effect on evolution. The extremely weak field could have enhanced hydrogen escape to space, leading to increased oxygenation of the atmosphere and oceans. In this way, Earth’s magnetic field may have assisted the radiation of the macroscopic and mobile animals of the Ediacara Fauna. Whether the Ediacara Fauna are genetically related to modern life is a matter of debate, but if so the magnetospheric control on atmospheric composition may have led to an acceleration in evolution that ultimately resulted in the emergence of intelligent life.