Video link to safe walking
Look at the picture of the Savanna. My teacher Master Stephen Hwa has said early humans had to walk very carefully with their weight back, not letting gravity pull the body forward in order to cope with such unstable ground in the night as well as day. If you are walking with weight back you are not pushing so much with the back foot as you are pulling with the front. With such pulling, the core will engage by default. This is not entirely correct and it is easy to hurt the legs this way. In Classical Tai Che we use the core to engage the legs. In this Youtube video link above, Master Stephen Hwa teaches you how to Tai Chi walk and use Tai Chi walk for everyday walking, how to engage the core, keep weight back, etc.