The earliest known iteration of the legend of Hua Mulan goes back to a 1500-year-old song about a woman who took her father's place in the army and became a war hero in disguise. The story may be even older in the oral tradition, and it may even have been rooted in fact. While there isn't any evidence of a warrior named Hua Mulan, anthropologists Christine Lee and Yahaira Gonzalez re-examined remains of 29 skeletons in Mongolia, and found two that are female and show evidence of warrior training. As quoted from New Scientist:
Three of the skeletons belonged to Xianbei women—and two were potentially warriors. Lee and Gonzalez reached this conclusion partly due to the nature of marks left on the bones where muscles once attached. The marks are larger if the muscle was heavily used, and the pattern of marks on both women’s skeletons suggests they had routinely worked the muscles someone on horseback would use. There were also indications that they practiced archery.
Christine Lee talked to Ars Technica about the implications of the find. -via Smithsonian