Aliens: Colonial Marines, won't be entirely male, the developer announced during a panel at last weekend's PAX Prime event in Seattle, WA. One female character named Jennifer Redding will be available in co-op, while the game's competitive multiplayer modes will include options for customizing different female marines.
Since the announcement was made, a 3,800-person strong internet petition to have female characters added to the game has taken credit, updating with a message that "the petition is a SUCCESS!!! CONGRATULATIONS EVERYONE!, and thank you for your support!"
Meanwhile, Gearbox CEO Randy Pitchford maintains that women were always part of the plan, according to Kotaku. Essentially, Gearbox had yet to complete the design work for Redding and the multiplayer models and did not want to unveil them until they were finalized. As the petition's online presence mounted, however, the developer felt it should show off the plans to resolve the situation.