Borders of life

Life on Earth has existed for at least three and a half billion years, and indirect evidence suggests it may be several hundred million years older still. During this time, it has undergone a breathtaking evolutionary development and changed the planet beyond recognition. Without it, Earth would never have become the blue-green jewel we admire today and call home. Although in its individual forms (living creatures) life may seem fragile and fleeting, in itself, throughout its existence—most of which was spent as single-celled organisms adrift in the oceans—it has demonstrated immense resilience and tenacity. It has gradually managed to colonise almost every conceivable environment, from hot springs and salt lakes to the driest deserts and mountain peaks. Follow in its footsteps to the most inhospitable places on Earth and explore the very boundaries of life.