In Chapter 1 some past major life extinction events on Planet Earth were highlighted, as were some of the survival mechanisms which have evolved to allow living organisms to cope with change. Before considering the factors which are responsible for the present anthropogenic extinction event which has begun to overshadow our wildlife, I would like to briefly look again at Earth history and to consider the evolution of life on Earth, so that present events can be seen in the context of previous changes.

Planet Earth is believed to have formed about 4600 million years ago (mya) from material revolving around the Sun. Soon after its birth, following a collision between Planet Earth and another planet (Theia), a series of small moonlets were spawned off, and these are thought to have coalesced to form our present Moon. The gravitational pull of the Moon is essential to life on Earth as we know it, since it helps stabilise the somewhat fluctuating axis of the Earth’s rotation and also provides the tidal changes of the world’s oceans. The atmosphere and oceans appeared on Earth about 4000 mya, and the earliest bacterial life forms probably appeared soon thereafter.