Most species are transitory. They go extinct, branch into new species or change over time due to random mutations and environmental shifts. A typical mammalian species can be expected to exist for a million years. Modern humans, Homo sapiens, have been around for roughly 300,000 years. So what will happen if we make it to a million years?
Some pretty heavy, but not unlikely food for thought in above linked article on ScienceAlert: What is our species headed for if we make it to the year one million, the average life cycle of any mammalian species? The scenarios depicted are not implausible – but in all honesty pretty uncomfortable to imagine…. But see for yourself.
Calculus of Decay 