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.
During the PermianâTriassic mass extinction event 252 million years ago, most life on Earth perished. Scientists have now obtained evidence that ocean acidification played a key role in the die-off. The new research was published in the journal Science on April 10, 2015. The PermianâTriassic mass extinction event is the largest such event to ever to have occurred on Earth. About 90% of all marine species and 70% of all terrestrial species died off during this time. It was much worse than the mass extinction event that killed off the dinosaurs 65 million years ago.