The Earth is about 4.54 billion years old and the earliest undisputed evidence of life on Earth dates from at least 3.5 billion years ago.

More than 99% of all species, amounting to over five billion species, that ever lived on Earth are estimated to be extinct.

Estimates on the number of Earth‘s current species range from 10 million to 14 million, of which about 1.9 million are estimated to have been named and 1.6 million documented in a central database to date, leaving at least 80% not yet described.

Evolution mainly works by natural selection. Animals and plants which are best suited to their environment will, on average, survive better. There is a struggle for existence.

Those who survive will produce The Next Generation. Their genes will be passed on, and the genes of those who did not reproduce will not. This is the basic mechanism which changes a population and causes Evolution.

The Next Generation can only come from those that survive and reproduce. After many generations of this, the population will have more helpful genetic differences, and fewer harmful ones.

Natural selection is really a process of elimination. The elimination is being caused by the relative fit between individuals and the environment they live in.