Portal was the first Valve-developed game to be added to the OS X-compatible list of games available on the launch of the Steam client for Mac on May 12, 2010, supporting Steam Play, in which players that had bought the game either on a Macintosh or Windows computer could also play it on the alternate system.
1 Eurasian Pleistocene megafauna became extinct in roughly same time period despite having a much longer time to adapt to hunting pressure by humans. 2  However, the extinction of the Eurasian megafauna can be viewed as a result of a different process than that of the American megafauna.
Cretaceous-Tertiary mass extinction 65 million years ago ; Mass extinction theories. Asteroid impacts, climate change, volcanoes - there have been many theories about the causes of mass extinctions. In some cases, such as the Cretaceous mass extinction event, more than one such factor was involved in the global catastrophe. 1  Catastrophic methane release. 2  Flood basalt eruptions. 3  Climate change. 4  Impact events.