A strengthened magnetic field around Earth could have allowed life to evolve beyond single-celled organisms starting 500 million years ago, The Washington Post reports. Life first evolved on Earth about 4 billion years ago, but it remained single-celled for the following 3 billion years. During that time, scientists believe that Earth lacked a solid core and thus had a much weaker magnetic field—something required to protect life on Earth from DNA-damaging radiation. But the solidification of Earth’s core about 500 million years ago created a stronger magnetic field just about the same time the sun started dialing down its barrage of radiation, scientists reported recently in Geoscience Frontiers. Together, these factors allowed life on Earth to begin its journey to complexity.