The Before website is now online, heralding development of Before, a new survival game set during the stone age from Facepunch Studios (RUST, Garry's Mod). This doesn't yet have a release date, but they say they are working "at the moment" towards creating a playable alpha, and that they hope to eventually release the Unity engine game to Windows, OS X, and Linux. This has been in the works for a while, so there are already a couple of updates on the game's development blog, the most recent of which includes a season transition timelapse trailer with a look at what they're working on, and there's an announcement trailer from the show. Here's a bit on the game:

Finding food and shelter is an everyday struggle; and keeping your tribe safe and healthy is not always a simple task.

Not only must the tribe hunt and forage each day, they must also protect their young, fend off wild animals and battle the elements.