With efforts to improve energy efficiency focussed on green transport to sustainable power generation, growing your own food to reducing waste, it's often easy to forget that the very buildings we live and work in could also be made energy efficient. But how do you retrofit old buildings without ruining their architectural character? One researcher from the UK Energy Research Centre explains where you might start. Scientists at the University of Birmingham tell Sue Nelson how they're trying to understand when and why humans developed the ability to walk on two legs; with the help of some... Like this podcast? Please help us by supporting the Naked Scientists