What causes new infections, like Covid-19, to emerge in the first place? Why does the same temperature seem to feel colder in the day than it does at night? Why have we locked down the world for Covid-19 when it seems less serious than we first thought? We also talk about the symptoms of long-Covid, and explain how the heart formed back in evolutionary history, with Dr Chris Smith and 567 CapeTalk's Kieno Kammies... Like this podcast? Please help us by supporting the Naked Scientists