The good news is that we can stop this mass extinction. Biologists predict that unless we change course and begin preserving more species, within the next few hundred years, we will become the cause of Earth's sixth mass extinction. I read about the 5th mass extinction about 11 000 years ago in North America. The sixth mass extinction “officially” started at about 12,000 year ago at the end of the last glaciation, ... Join us for the next part in this series as we look at the basic causes of modern mass extinction. Sixth Mass Extinction Really Started Thousands of Years Ago. David McNew/Getty Images. 11. Working on biodiversity lost, I would like to have more details about this sixth mass extinction. The sixth mass extinction, explained. It began about 50,000 years ago, when modern man first left Africa. The populations of the world's wild animals have fallen by more than 50 percent and humanity is to blame. Since then, it seems to have been nothing but havoc. February 17, 2019. The Sixth Mass Extinction, also known as the Sixth Extinction or the Holocene extinction event, is an ongoing extinction event perpetrated by human beings.