Bob Engleman, PAI's director for population and environmental programs, notes that there are plenty of instructive examples of devastated ecosystems ruined by human population pressure, dating back to the possible extinction of mega-fauna like the mastadon
and sabre-toothed tiger at the hands of man in North American prehistory.
Lenz (2001) hypothesized that beginning in the middle Miocene (15.1-11.2 mya) mammals such as gomphotheres, mastadons
and mammoths likely were long distance dispersers of Joshua tree seeds.
In fact, elephants seem to have evolved far many more pairs than even their direct genetic ancestors like the woolly mammoths and mastadons
. The researchers also experimented with elephant cells, by exposing them to chemicals and radiation.