It is histort which poroves the point. The Roman empire was in existence for a few hundred years prior to becoming Christian. The Romnans developed a court system open to the people. The laws were in effect before anyone there heard of the 10 commandments.
I will not be so prsumptious as to try to give you a history lesson. The information is all around the library and maybe even on the internet, which you sourced.
Another point is that half or more of the commandments are not codified in our laws. So my conclusion is that it was a 50% effort.
Answer not a fool according to his folly, lest thou also be like unto him.
Proverbs 26:4