Australasian Science: Australia's authority on science since 1938

Is Intelligence Out There?


Is human-like intelligence too much to expect?

By Stephen Luntz

Intelligence may not be the ultimate outcome of evolution on Earth, so why should we expect human-like intelligence elsewhere in the cosmos?

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. To expect anything else is a form of arrogance, he believes.

In 1960 the Search for Extra-Terrestrial Intelligence (SETI) started with high hopes. Radio telescopes searched increasingly large areas of the sky over more and more wavelengths, seeking communication from other planets. The idea is so popular that, when government support was withdrawn, private donors stepped in – hardly a common event in science. Hundreds of thousands of people have set their home computers to seti@home to assist with data processing.

Yet the longer we go on without a whisper, the more the question starts to arise: why the silence?

Some theories have been rejected. At one time it was thought that planets might be rare, so that only in the most exceptional circumstances would life be given an opportunity to form. We now know that at least 10% of sun-like stars host planets, and it is possible that almost all do.

We also know that life formed on Earth almost as soon as it was possible for it to do so, suggesting that it is unlikely for life to be a rare phenomenon in the universe.

Other theories have suggested that, while life is common, technology requires circumstances that are unique to Earth. Various scientists have proposed that the presence of a moon as large as our own is essential to stabilise axial tilt, and therefore the climate, or to create an intertidal zone that would allow species to leave the oceans.

Lineweaver, however, believes that it is not the conditions required for technological development that are lacking. Rather, there is no reason for intelligence to form – even under favourable conditions.

Not the Planet of the Apes
Lineweaver calls this the Planet of the Apes hypothesis – the idea that there is an intelligence niche that one or more species will inevitably evolve to fill.

The name comes from the 1968 film, which was remade in 2001. In it, human civilisation is wiped out, and when a band of astronauts return to Earth they discover that gorillas, chimpanzees and orangutans have evolved speech, tool use and a moderately high-tech civilisation.

Most viewers probably realised that it was not very likely that three distinct ape species would evolve intelligence at the same time, or that their civilisation would so closely parallel our own. Nevertheless, Lineweaver argues that the film plays to our belief that there is something reasonably automatic about the evolution of intelligence. After all, being smart enables one to outwit predators and use tools to catch prey.

Surely with enough time one species on a habitable world will develop technology to the point where we can communicate, and perhaps even trade, with them?

The problem, Lineweaver argues, is that the hypothesis doesn’t fit the evidence. Humans evolved in Africa. Meanwhile in Asia, Australia and North and South America ecosystems rose and fell, and species came and went, all without the slightest hint of developing human-sized brains, opposable thumbs or control of fire. If there is an “intelligence niche”, why did no species rush to fill it in on other continents?

Indeed, Lineweaver says that the sample size is larger than this, as some large islands such as Madagascar are effectively isolated worlds where millions of years of evolution could have produced intelligent species, but didn’t.

Big brains have advantages, but they have drawbacks too, including the need for lots of energy. One-quarter of our food consumption is needed to keep our brains ticking over. This price must be paid before most of the benefits of a large brain can be realised.

Of course, there are plenty of smart species out there. Chimpanzees, dolphins and even New Caledonian crows (AS, Jan/Feb 2008, p.19–21) have amazed us with their achievements. However, none are remotely close to building radio telescopes and chatting with other planets. Nor is the problem that we have cruelled their pitch – many of these species were around long before we were.

Lineweaver’s critics are fond of pointing to a graph produced by brain scientist Dr Harry Jerrison, which plots an encephalisation quotient with time. The encephalisation quotient is calculated by dividing the weight of a species’ brain by the weight of its body. When mapping species on this graph we see a general trend for brains to become relatively larger in more recently evolved species. Given time, Jerrison’s followers argue, intelligence will achieve lift-off.

Once again, Lineweaver thinks that this approach is simply looking at the world through human eyes, and calls his opponents “brain worshippers”.

“Naturally we think we’re the best, and everything should become like us,” Lineweaver says. “Imagine if the question was being put by elephants. They would look around and ask what it was that made them the best species, and conclude it was having a really long nose.”

These elephants, Lineweaver believes, would construct a “nasalisation quotient” by graphing the length of noses over time. Such a chart would produce a trend to longer noses for one simple reason – the elephants and their closest relatives were on it and skewed the data. Lineweaver’s elephants would conclude that nasalisation was an inevitable consequence of evolution, and they represented the epitome of this trend, rather than an exceptional outlier as we see them.

Lineweaver sees our enormous brains in similar terms: a freak occurrence that evolved just once. No matter how long they had, kangaroos were no more likely to evolve super-sized brains, Lineweaver believes, than they were to evolve long trunks.

Thinking that big brains are inevitable is a form of arrogance, Lineweaver believes. Just as elephants could not believe that everyone wouldn’t want a long trunk if they could only get one, we assume that our defining feature is desirable for all.

Defining Intelligence
Part of the issue is how we define intelligence. There are countless examples of animals that display remarkable reasoning skills or tool use, but we’re not really interested in meeting the Alpha Centaurian version of a dolphin. We want something with “human-like intelligence”.

Lineweaver says that we have defined this intelligence as something that no other animal on Earth has. “Other species on Earth are our nearest relatives. Our DNA and evolutionary history makes us much more closely related to a dolphin than any species from another world,” Lineweaver argues. “If we’ve defined human-like intelligence so that no animal related to us meets it, what are the chances for something with a completely different evolutionary history?”

Indeed, Lineweaver thinks that even if a trend towards intelligence was established among species on Earth there is no reason to believe it would be universal. “For 98% of our evolutionary history we were the same as dolphins, so if they show a trend towards bigger brains it could be from programming somewhere back in our shared history.”

Even the development of a head is something that Lineweaver says only evolved once, and while it has proved highly valuable for colonising the planet, no other phyla have repeated the move. Perhaps on some other world there are millions of species that wouldn’t even know where to store a large brain if they had one.

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 was part of research that helped to define the area of the galaxy in which it might be worth seeking advanced life (AS, April 2004, p.14–16). Further out than this “habitable zone”, stars lack the metallicity needed to support rocky planets like our own. Further in, frequent supernovae and other disturbances would disrupt the slow process of evolving advanced life forms. Lineweaver stands by this work.

The Other Side
Lineweaver says he is at one end of a spectrum among astrobiologists over the likelihood of human-like intelligence developing elsewhere. At the other end is Prof Simon Conway Morris, a British evolutionary palaeobiologist at Cambridge University and author of Life’s Solution. Conway Morris spells out his position in the subtitle: Inevitable Humans in a Lonely Universe.

Conway Morris believes that intelligence is a convergent feature of evolution, rather like the eye. It is believed that eyes similar to our own have evolved at least six times during the course of life on Earth – they’re just so useful that species without them keep on inventing them. If intelligence is like this then all you need is a suitable planet and plenty of time and you’ll have vaguely humanoid creatures for us to communicate with.

Conway Morris blames the absence of evidence for intelligent species on a shortage of suitable worlds, maintaining that most apparently Earth-like planets would lack key features that make it possible for intelligence to evolve. For example, some planets may have too much or too little water, or be subject to far more frequent asteroid bombardment, knocking out species just as their brains were starting to grow.

Lineweaver says that most astrobiologists fall somewhere in between. They hold that intelligence may not be inevitable, but given enough planets it will turn up now and then.

Dr James Benford is a physicist who has spent most of his career building high-power microwave transmitters. He became interested in SETI, and concluded that most of the searches were being conducted in the wrong part of the radio spectrum (see box, p.37).

Benford visited Australia last year, and gave a lecture entitled: “Rethinking the Search for Extraterrestrial Intelligence 50 Years On”. While he acknowledges that radio telescope-building species may be rare, he is skeptical of Lineweaver’s conclusion. “Charlie believes the number of intelligent species in the universe is one. It’s not zero, it’s not two or ten. It’s one. That seems to me an overly precise estimate.”

Asked for his own opinion he says: “What everyone in the SETI discussion tries to do is answer Fermi’s question: ‘Why aren’t they here’. On a lot of grounds we should already have evidence for them. Fifty years of searching has not succeeded.

“I prefer to put it this way. It’s possible intelligent civilisations are separated by very large distances. We’ve only really been conducting searches that would pick things up within 1000–2000 light years, and the total observing time over those 50 years is measured in months. Quite possibly life is very rare – the only way to test this is to keep looking.”

Benford has no doubts about the value of the search. “We don’t know how likely it is for life to form and for it to become intelligent. Other searches might show evidence of life, but if we find evidence for intelligence we instantly know so much more. It’s like Robinson Crusoe finding that footprint on the beach – you learn so much from a single observation.”

Prof Malcolm Walter, an astrobiologist at the University of NSW, doesn’t have quite the confidence that Lineweaver has. “The problem of calculating how many civilisations there are is that we don’t understand the origins of life,” Walter says. “We have a good understanding of the evolution of intelligent mammalian life, but without better understanding can’t really predict the probability of intelligent life elsewhere.”

Nevertheless, Walter suspects that Lineweaver is broadly right in his conclusions: “Most people working in the field would agree with the improbability of finding industrial civilisations out there.”

Home Alone
It’s hard to fathom the implications for how we see ourselves if Lineweaver’s view gains widespread acceptance, but they would probably be profound. Before science fiction got us used to thinking that we share the galaxy with aliens we believed in angels, and before that fairies and a multiplicity of gods.

If we saw ourselves as truly unique in the universe we might prize ourselves and our planet more highly, but we might also have more cause to doubt whether there was any purpose to our existence. Such a conclusion wouldn’t be very welcome to the folk at SETI, and the astrobiological community in general.

Lineweaver thinks there is likely to be life on many planets. However, the idea of discovering something equivalent to blue-green algae, or even advanced but non-technological megafauna, is unlikely to open the purse strings for more research.

Lineweaver himself still believes that SETI has value. “There are many examples of developing a new technology and looking in a new place and finding something unexpected,” he says. “SETI is developing the most sophisticated frequency analysers of anyone, and looking at frequencies normal astronomers don’t look. It’s also very cheap, and we should never turn down new research on the cheap.”

Lineweaver 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. He also acknowledges that, as confident as he is in his conclusions, there’s a possibility he is wrong.

However, it is doubtful how well these arguments will succeed with a wider community who, perhaps naively, is hoping that one day soon SETI will pick up evidence of a beacon of interstellar communication. Asked to imagine what the species producing such communication might look like, its likely many people will imagine a bipedal species with a head, eyes and a mouth. Something, that is, rather like an ape.

The four key factors determining the relative likelihood of complex life existing at any point in time and space are:

1. Availability of Potential “Parent” Stars
To make a home for complex life there needs to be a host star that is stable for long enough (i.e. at least a few billion years) to allow life to evolve.

2. Metal Abundance

Heavy elements (known as “metals”) must be available to form planets, but not too many as this encourages the formation of giant gas planets and precludes the presence of terrestrial planets.

3. A Safe Environment
The development of complex life requires a calm environment that is sufficiently far from massive dying stars, whose violent death throes release tremendous amounts of energy in the form of radiation and cosmic rays.

4. Time to Evolve
On Earth, the timescale for multicellular life to blossom was about 4 billion years, and this value is assumed to be typical. This condition ensures that a region that has only recently met the first three conditions has a low relative likelihood of hosting complex life, but may contain “simple” microbial life.

Are We Looking in the Wrong Place?

If human-like intelligence is not unique in the universe, why have we not found any evidence of other species that got here before us? Dr James Benford has his own take on this question. He thinks we have been searching in the wrong part of the radio spectrum.

“Unless it was very close, the searches we have done so far would not have picked up any beacon we would build,” Benford says. The assumption in the past is that aliens would communicate in ways that are optimised for the receiver. Since water is considered essential for life it is assumed any species will be interested in studying water in the universe, so researchers have looked for signals near the “waterhole” – the frequencies emitted by hydrogen and hydroxyl ions. It is assumed that just as animals can be found clustering around real waterholes, interstellar communication will be based near these frequencies.

However, the widespread presence of these molecules also clutters up transmission at such wavelengths. To provide an easily detected signal it is much cheaper to operate in the higher frequency microwave bands, and to use a directed pulsed beam rather than something that runs all the time and can be picked up in a quick search.

Such messages are likely to be “more like Twitter and less like War and Peace,” Benford says. More detailed messages could be sent at much lower power and nearby frequencies that are detectable only to those already alerted to their presence.

“Cost has always mattered,” Benford says. “It mattered for the pyramids and it matters for us today.” Even though civilisations far more advanced than our own may be unimaginably wealthy by our standards they will still have to choose how many resources they put into communicating with those less advanced than themselves. If the answer isn’t much they’ll send messages where it is cheap for them rather than easy for us to find.

Benford co-published his ideas online with his twin brother, astrophysicist Gregory Benford, as Searching for Cost-Optimized Interstellar Beacons. The paper has attracted much attention. The twins also argue that we should spend less time looking at nearby stars and more time focused on the centre of the galaxy, where most stars are clustered.