would think that just in contemplating these different scenarios it would be easy to fall into the la markanrip about these. the way that -- i don't know. maybe by the time you're in your position not but i don't know, for the layman that we about a pretty easy trap to fall into. >> so, i'm a darwin union -- darwinian graduate and i think it's probably happened gradually, and i think there's probably not one explanation for why bipedalism assed a invokous but was- -- advantageous and search north answer is wrong-headed. so, you have a population and variation and there's certain individuals that move bipedally more than others and they have more food and more reproductive opportunities and offow go. we're trying to figure out what allows to the individuals to have more food and more reproductive opportunities there oar scholars that think was more la markan, this was -- richard dawkins has written but that. things biteedallism emerged as a meme, cool thing to do, and that chimpanzees, gorilla's occasionally move two-legs and if that became the fad in that population you could have more and m