Governments should prepare for the worst if aliens visit earth because beings from outer space are likely to be just like humans, a leading scientist is claiming.

Extra-terrestrials might not only resemble us but have our foibles, such as greed, violence and a tendency to exploit others’ resources, says Simon Conway Morris, professor of evolutionary paleobiology at Cambridge University.

And while aliens could come in peace they are quite as likely to be searching for somewhere to live, and to help themselves to water, minerals and fuel, Conway Morris will tell a conference at the Royal Society.

His lecture is part of a two-day conference at which experts will discuss how we might detect life on distant planets and what that could mean for society. “Extra-terrestrials … won’t be splodges of glue … they could be disturbingly like us, and that might not be a good thing – we don’t have a great record.”

The US space agency’s search for alien life is based upon the mantra “follow the water”, a strategy reflecting the fact that, on earth, where there’s water there’s life.
Astronomers have detected more than 400 planets outside our solar system, some of which sit in the “Goldilocks zone” where the temperature is neither too hot nor too cold for liquid water to form.

Conway Morris will argue that alien life is most likely to occur on a planet similar to our own, with organisms made from the same biochemicals. The process of evolution will even shape alien life in a similar way, he added.