Evolution is change in the heritable characteristics of biological populations over successive generations.[1][2] Evolutionary processes give rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms, and molecules.[3] All life on Earth shares a common ancestor known as the last universal common ancestor (LUCA),[4][5][6] which lived approximately 3.5–3.8 billion years ago,[7] although a study in 2015 found "remains of biotic life" from 4.1 billion years ago in ancient rocks in Western Australia.[8][9] In July 2016, scientists reported identifying a set of 355 genes from the LUCA of all organisms living on Earth.[10]