7/7. We Are the Aliens. From time to time we might comment that someone is from another planet, but are we all in fact descended from extra-terrestrials?
Panspermia, the theory that life first arrived on Earth from other worlds, was ridiculed when it was first mooted back in the 1960s, but in the past ten years the idea has gained ground with scientists. So the question remains - is my stepmother an alien? Horizon returns in the new year. Director/Producer Andrew Thompson
See also The Martians and Us, tomorrow at 7pm on BBC4