One of the oldest Japanese Martial Arts that probably had an influence on Ju-jitsu’s development was the Wrestling Sport Chikura Kurabe, that was first practiced around 230 B.C. It contained some techniques simular to Ju-jitsu.
There are several theories as to how Ju-jitsu evolved. Some Martial Arts historians believe that Greek Pankration may have had an influence on Jui-jitsu, and after Pankration was brought to India by Alexander the Great’s invading army, these techniques made it to China and then to Japan.
Some techniques of these two Martial Arts were simular, and both employed the use of joint locks, choke holds and throws. Both were excellent Combat Arts for use on the battlefield.
The Chinese Grappling art of Chin Na was a Martial Art that was documented to have influenced Ju-jitsu. A man named Chin Gempin told three masterless Samurai that there was an art in China of “seizing a man,” and he gave them a brief demonstration of what he had seen.
The Samurais were intrigued and went off to learn more of this art and after some time they reached a level of expertise and returned to teach these techniques.
But there were Ju-jitsu schools already in existance before Chin Gempin was even born. Takenouchi-Ryu founded in 1532 is one of the oldest Ju-jitsu schools, and is still in existence.
There were hundreds of styles of Ju-jitsu and no two styles evolved the same way.