The early UFCs were based on the Vale Tudo matches in Brazil where "anything goes" and "the rules are there are no rules".
Rorion Gracie's original vision was an open contest where any fighter from any background could face any other fighter with no time limit, no weight category, no protection, no rules.
What is now called MMA today, as can be seen in modern UFC among other events, had it's origins in this brutal Vale Tudo.
Have a look at some of the early UFC matches that have a great significance on the way everyone trains and fights today.