As mobile heterotrophs, animals necessarily interact with many other species. Their natural proclivity to extensive ecological encounters radically altered the gyre of life from that which existed prior to their emergence. One of the most recent mammals to descend – a gracile, bipedal simian who thought itself ruler of the world – would tilt the gyre like no other.
A billion distinct animals have lived since the emergence of animals; over 97% of them invertebrates. Over 20 million animal species have graced the planet since the descent of humans. That number has inexorably dwindled as the global human population has proliferated, and much more rapidly in the past century, though with little concern of consequences by its instigator.