Early in the 20th century planet Earth was home to more living species than ever before, although this represents only about 1% of all species that have ever lived at some time in the past. The other 99% of life forms had become extinct, which is a natural process of evolution.
In the history of life on Earth, there have been five events of major mass extinctions.
In four of these, more than three-quarters of the species alive at that time abruptly disappeared.
Since the mid-20th century, humankind has been responsible for the premature extinction of many species, and if we continue at this rate, we will precipitate the sixth event of mass extinction.
Sadly, there is no indication that we have the will to prevent this from happening, so that the 20th and 21st centuries will probably not be remembered for our technological advances, but rather for our unwillingness to prevent the sixth extinction.
Source information: The story of life & the environment an African perspective.