Laughing probably does play a role in memory recall and establishing beneficial social arrangements. I don't know if it's massively influencial in who we build friendships with, since it seems to be a general rule that we're drawn to people with similar values / tastes when it comes to finding freinds.

In other words, I'm not sure the purpose of laughter is to signal compatibility, because that function does not seem to be unique to laughter, and generally each evolved behaviour has at least one distinct purpose.

It probably is part of the process of matchmaking though.

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With regards to modern culture, I wonder if it is more the case that our humour is largely the same as it was 2000 years ago, but that the setting it is present in has changed. I moved to a wealthy city recently and one profound thing I noticed was that no one here is funny or laughing much. Humour is almost dead, but go to a comedy show and they laugh constantly and often at stupid things. Has people's sense of humour change much, or is it their environment that has changed? Probably a mix of both, but I think environment is a factor too. I think people are a lot more pessimistic then they would of been 2000 years ago (which initially seems silly, but we're able to percieve more threats in the modern world than we could back then).