Many UFO researchers conclude that the most likely explanation for the UFO phenomenon is that it is due to extraterrestrial visitors. If one accepts this hypothesis,then a logical part of this, is that there must be intelligent life out there in the cosmos, for it to be visiting us on Earth.
Some in mainstream science disagree about the intelligence part. One of the proponents of an alternative view is Dr Charlie Lineweaver. The magazine "Australasian Science" Volume 32, number 1, dated Jan/Feb 2011, pages 34-37 carries an article by Stephen Luntz titled "Is there intelligence out there?"
"Dr Charlie Lineweaver has presented a new take on the question of whether we are alone in the universe. He argues that the chance we will ever encounter an alien species with "human-like" intelligence is vanishingly small."
At one time, planets were thought to be rare, but now it is estimated that 10% of sun-like stars have planets.
In addition, as life started on Earth almost as soon as it was possible for it to do so, it is therefore argued that life in the universe would be common.
"Lineweaver, however, believes that it is not the conditions required for technologicl development that are lacking. Rather, there is no reason for intelligence to form-even under favourable conditions."
"Lineweaver calls this the Planet of the Apes hypothesis - the idea that if there is an intelligence niche that one or more species will eventually evolve to fill it."
"Lineweaver argues that the hypothesis doea not fit the evidence." Humans evolved in Africa, and although there were other places on Earth that we could have risen from, we did not. No where else on Earth did intelligent human life come to be.
Dr Harry Jerrison, a brain scientist, plotted encephalisation quotient versus time, on a graph. The graph indicated that brains became larger over time.
Lineweaver says "...this approach is simply looking at the world through human eyes...Lineweaver sees our enormous brains in similar terms, a freak occurrence that evolved just once..."
"Indeed, Lineweaver thinks that even if a trend toward intelligence was established among species on Earth there is no reason to believe it would be universal."
"The theory that it is human-like intelligence that is improbable, rather than life itself, resolves the apparent contradiction between Lineweaver's latest work and some of his earlier research."
Lineweaver says he is at one end of a spectrum of opinion. At the other end is Professor Simon Conway Morris who believes intelligence is inevitable and that vaguely humanoid creatures are out there.
In between, most astrobiologists say that given enough planets, intelligence will arise.
For those who think there are intelligent civilisations out there, Dr James Benson "concluded that most of the searches were being conducted in the wrong part of the radio spectrum." "It's possible intelligent civilisations are separated by very large distances."
Professor Malcolm Walter, an astrobiologist at the University of New South Wales suspects "that Lineweaver is broadly right in his conclusions. Most people working in the field would agree with the improbablity of finding industrial civilisations out there."
"Lineweaver thinks there is likely to be life on many planets....and himselef still believes that SETI has value..." However, "...he believes that SETI could turn out to be like Columbus: searching somewhere new based on a bad hypothesis but finding something of even greater value."