I restarted Tor to get the automatic update, but now my computer is telling me that it can't run the new version -- that it doesn't support my computer. I have an OS X 10.8.5. Is there a way to use the previous version of Tor? I haven't found a way on my own.
It is best to update your Mac so you get all the latest security patches. After you update your Mac to the latest stable version macOS 10.12.5 Tor Browser should start working.
Here are the latest security patches for macOS. https://support.apple.com/en-us/HT201222
Also there are serious security bugs that have been fixed in the latest versions of Tor Browser Bundle. Here are just some of the security fixes for Tor browser. Using outdated versions of software puts you at risk of attackers using known vulnerabilities that have been fixed in latest versions to compromise your real ip.