Professor Simon Conway Morris at Cambridge University will tell a conference on alien life that extraterrestrials will most likely have evolved just like "earthlings" and so resemble us to a degree with heads, limbs and bodies.
Unfortunately they will have also evolved our foibles and faults which could make them dangerous if they ever did visit us on Earth.
The evolutionary paleobiologist's beliefs mean that science fiction films such as Star Wars and Star Trek could be more accurate than they ever imagined in depicting alien life.
Prof Conway Morris believes that extraterrestrial 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.
“It is difficult to imagine evolution in alien planets operating in any manner other than Darwinian," he said.
"In the end the number of options is remarkably restrictive. I don't think an alien will be a blob. If aliens are out there they should have evolved just like us. They should have eyes and be walking on two legs.
"In short if there is any life out there then it is likely to be very similar to us."
Extra-terrestrials might not only resemble us but have our foibles, such as greed, violence and a tendency to exploit others' resources, claims Professor Conway Morris.
They could come in peace but also be searching for somewhere to live, and to help themselves to water, minerals and fuel he is due to tell a conference at the Royal Society, in London.
However he also thinks that because much of the Universe is older than us they would have evolved further down the line and we should have heard from them by now.
He believes it is increasingly looking like they may not be out there at all.
Thoughts on this?
Conway Morris is a big hitter in the scientific establishment. He is, however, a theist, and has "argued against materialism" according to wikipedia. But what are his arguments? Alas the press piece doesn't say. Kudos to anyone who finds the conference and posts the arguments.
“It is difficult to imagine evolution in alien planets operating in any manner other than Darwinian,"
Is this just an instance of a slightly woo scientist-theist failing to take into account that nature might be more imaginative than him?