By SARAH GRIFFITHS
PUBLISHED: 17:48 GMT, 14 November 2013 | UPDATED: 00:32 GMT, 30 September 2014
- A U.S. ecologist says conditions such as bad backs and sunburn suggest humans did not evolve alongside other life on Earth
- In a new book, Dr Ellis Silver says aliens put humans our planet as recently as tens of thousands of years ago
- He suggests the Earth might be a prison planet, since humans seem to be a naturally violent species and are here until we learn to behave ourselves