Not so.As Censored says, OS X came out of NextStep which means that it predates Ubuntu.
Ubuntu came before OS X, since OS X was developed as a mutant form from NextStep which went back to open source BSD.
As censored notes: OSX relies on a slew of open source tools, many of which owe much of their development to Linux-based developers.
Therefore it's best to view OS X as a mongrel bastard of Unix/BSD/Darwin/Linux open source development....