The earth has a finite lifespan

The earth has a lifespan of about 12 billion years before it will be destroyed or seriously burned by the Sun when it becomes a red giant star. Earth is now about 4.5 billion years old and the age of animals started at around 4 billion years - and will probably only last until about 5 billion years - there is a predictable sequence for the breakdown of habitability of the earth, due to the increasing luminosity of the sun and its consequences.

Every species has a finite lifespan due to changing conditions on the earth . Think of the age of the earth as a clock starting at 12 noon and ending at 12 midnight- each number on the clock represents 1 billion years. The end of the Earth will be at midnight. First life was around 1pm, oxygen appeared in the atmposphere just after 2pm, the age of animals started at 4pm and it is now 4.30pm. The age of animals will probably end at around 5pm and the age of man is the blink of an eye.

Ref "The Life and Death of Planet Earth" by Peter Ward and Donald Brownlee first published 2002