We are, in fact, in the early parts of a mass extinction that we are causing. Here's a scholarly article for you: https://static.squarespace.com/static/51b078a6e4b0e8d244dd9620/t/538797c3e4b07a163543ea0f/1401395139381/Pimm+et+al.+2014.pdf
The authors (S. L. Pimm,1* C. N. Jenkins,2 R. Abell,3† T. M. Brooks,4 J. L. Gittleman,5 L. N. Joppa,6 P. H. Raven,7 C. M. Roberts,8 J. O. Sexton9) -- because real science is done by teams of scientists checking each other's work -- say, "Current rates of extinction are about 1000 times
the likely background rate of extinction. Future rates depend on many factors and are
poised to increase."