"Humans… have pursued our distinctively destructive path for a sliver of the total biotime in this corner of the galaxy. This most recent reshaping of nature began 3.3 million years ago, when an australopithecine made stone tools to butcher animal carcasses on the shores of the Jade Sea, or Lake Turkana, in Kenya. Weapons came later, with the use of stone-tipped thrusting spears by another hominid in South Africa 500,000 years ago, and the development of the bow and arrow by early humans 71,000 years ago. Projectile weapons, like the bow and arrow, allowed us to kill large animals without being excessively brave. Through a combination of these weapons, coupled with traps and fire, humans saw to the extinction of woolly mammoths, mastodons, sabre-toothed cats and ground sloths as the ice sheets receded and we pursued the animals to their last redoubts. A South American armadillo-like animal called Glyptodon was another victim of the genocide. This slow-moving vegetarian was as big as a Volkswagen Beetle and served as an easy target for hunters who ate its meat and crawled into its enormous shells for shelter. For many years, biologists argued that climate change was the most important factor in these extinctions, but more and more evidence points to the correspondence between the arrival of humans and the disappearance of large mammals. The case was pretty obvious for the spectacular bird life of islands, with a giant turkey called Sylviornis disappearing from New Caledonia soon after the prehistoric Lapita people arrived in their canoes 3,500 years ago, and the elimination of numerous species of flightless moa when the Maori reached New Zealand around AD 1300. Extinction has been reworking nature from its beginnings, but no animal has come close to having the impact that humans have had. With remarkable speed, our evolution walloped life with the power of the asteroid that obliterated the dinosaurs. The average size of mammals increased steadily throughout the Cenozoic Era that followed the crash of the Chicxulub asteroid in the Gulf of Mexico 65 million years ago. Then, around 100,000 years ago, the big animals began to disappear. The extinctions accelerated 50,000 years ago and the total mass of wild mammals has now plunged to a sixth of its pre-human maximum. According to some models, the domestic cow is on track to become the largest remaining mammal. Scepticism surrounding these doom-laden predictions about the precarious nature of nature is understandable. It takes imagination to escape from the influence of the diminishing expectations of each generation. Nobody has seen a live moa since the fourteenth century and so their absence does not upset New Zealanders today. The last passenger pigeon, named Martha, died… in 1914, and the most recent sky-darkening mass migrations of these birds took flight in the nineteenth century. We cannot miss something that has never existed for us. We read about extinction as an approaching horror and ecosystem damage as a work in progress rather than a done deal. But the destruction is unabated. Despite the publicity given to deforestation, tropical woodlands continue to disappear at an annual rate of 2.7 million hectares in Brazil, 1.3 million hectares in Indonesia and 0.6 million hectares in the Democratic Republic of Congo. Turning to the direct effects of climate change, one-third of the world’s coral reefs were damaged by high water temperatures in 2016. More than 90 per cent of Australia’s Great Barrier Reef was affected by the process called bleaching, which happens when the dinoflagellate algae abandon their animal partners in the exquisite coral symbiosis. When reefs recover from bleaching, the original animals are replaced by sluggish coral species that support impoverished communities of marine life. This is not a normal phenomenon."