Is paleohacks.com a knockoff stackexchange site? Or is it an old SE site prior to Area51 creation? If it is legitimate, then the paleo-life proposal is likely a duplicate. However, I don't see paleohacks.com integrated into the rest of the site...
Paleo Hacks is leftover from the days of Stack Exchange 1.0.
Basically, the first crop of sites came from a model in which we sold our engine to anyone who wanted a site. The vast majority of these sites failed, so SE 2.0 - complete with Area 51 - was formed.
We allowed some SE 1.0 sites to continue operating under their original terms: content was owned by the people who owned the site (not SE, and not subject to our licensing), and we would not be giving them any new features or major changes to the core engine. Some 1.0 sites migrated to the SE 2.0 engine and continued to be part of the Stack Exchange network (OnStartups is the largest), but there are still a handful of sites that are operating as independent third parties.
You can read more about the 1.0 versus 2.0 modeling in an old company blog post.
As far as merging goes: if the paleo-life proposal gets all the way through the Area 51 process and becomes a site in the Stack Exchange network, we'll deal with it properly then. The most obvious thing to do is to reach out the owners of paleohacks.com and ask if they'd like to rejoin the Stack Exchange network, in which we could migrate their content to our 2.0 engine and allow the Area 51 followers to join with the already-existing paleohacks.com community. We'll cross that bridge when we get to it, though. :)