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.
Clues from the fossil record give us information about what species went extinct and when, but how the extinction happened in the first place has been a puzzling question for scientists. One of the biggest theories involves a series of volcanic eruptions, which took place about 250 million years ago in Siberia. According to Smithsonian's Mass Extinction, these eruptions spewed enough lava to bury the continental US under a layer 1,000 feet deep. Wikimedia Commons Part of the Siberian traps.