Simon is joined by Lorcan McGrane to judge suggestions for future humans by Helen Arney and Tony Bjourson.
The panel discuss fecal transplants, and then more about fecal transplants. There is talk of beards for all, and we find out why Helen Arney's ukelele never gets any bigger.
Our theme music was written and performed by Laurence Owen. Graphics by Theo Weedon, web design by Ian Bridgeman and support from the Wellcome Trust. The producer is Rachel Wheeley.