Some songs just won't leave you alone. But this may give us clues about how our brain works

A Everyone knows the situation where you can't get a song out of your head. You hear a pop song on the radio - or even just read the song's title and it haunts you for hours, playing over and over in your mind until you're heartily sick of it. The condition now even has a medical name 'song-in-head syndrome'.

В But why does the mind annoy us like this? No one knows for sure, but it's probably because the brain is better at holding onto information than it is at knowing what information is important. Roger Chaffin, a psychologist at the University of Connecticut says, 'It's a manifestation of an aspect of memory which is normally an asset to us, but in this instance it can be a nuisance.'

С This eager acquisitiveness of the brain may have helped our ancestors remember important information in the past. Today, students use it to learn new material, and musicians rely on it to memorise complicated pieces. But when this useful function goes awry it can get you stuck on a tune. Unfortunately, superficial, repetitive pop tunes are, by their very nature, more likely to stick than something more inventive.

D The annoying playback probably originates in the auditory cortex. Located at the front of the brain, this region handles both listening and playback of music and other sounds. Neuroscientist Robert Zatorre of McGill University in Montreal proved this some years ago when he asked volunteers to replay the theme from the TV show Dallas in their heads. Brain imaging studies showed that this activated the same region of the auditory cortex as when the people actually heard the song.

E Not every stored musical memory emerges into consciousness, however. The frontal lobe of the brain gets to decide which thoughts become conscious and which ones are simply stored away. But it can become fatigued or depressed, which is when people most commonly suffer from song-in-head syndrome and other intrusive thoughts, says Susan Ball, a clinical psychologist at Indiana University School of Medicine in Indianapolis. And once the unwanted song surfaces, it's hard to stuff it back down into the subconscious. 'The more you try to suppress a thought, the more you get it,' says Ball. 'We call this the pink elephant phenomenon. Tell the brain not to think about pink elephants, and it's guaranteed to do so,' she says.

F For those not severely afflicted, simply avoiding certain kinds of music can help. 'I know certain pieces that are kind of "sticky" to me, so I will not play them in the early morning for fear that they will run around in my head all day,' says Steven Brown, who trained as a classical pianist but is now a neuroscientist at the University of Texas Health Science Center at San Antonio. He says he always has a song in his head and, even more annoying, his mind never seems to make it all the way through. 'It tends to involve short fragments between, say, 5 or 15 seconds. They seem to get looped, for hours sometimes,' he says.

G Brown's experience of repeated musical loops may represent a phenomenon called 'chunking', in which people remember musical phrases as a single unit of memory, says Caroline Palmer, a psychologist at Ohio State University in Columbus. Most listeners have little choice about what chunks they remember. Particular chunks may be especially 'sticky' if you hear them often or if they follow certain predictable patterns, such as the chord progression of rock 'n' roll music. Palmer's research shows that the more a piece of music conforms to these patterns, the easier it is to remember. That's why you're more likely to be haunted by the tunes of pop music than by those of a classical composer such as J. S. Bach.

H But this ability can be used for good as well as annoyance. Teachers can tap into memory reinforcement by setting their lessons to music. For example, in one experiment students who heard a history text set as the lyrics to a catchy song remembered the words better than those who simply read them, says Sandra Calvert, a psychologist at Georgetown University in Washington DC.

I This sort of memory enhancement may even explain the origin of music. Before the written word could be used to record history, people memorised it in songs, says Leon James, a psychologist at the University of Hawaii. And music may have had an even more important role. ‘All music has a message.' he says. ‘This message functions to unite society and to standardise the thought processes of people in society.’

Can the future population of the world enjoy a comfortable lifestyle, with possessions, space and mobility, without crippling the environment?

The world's population is expected to stablize at around nine billion. Will it be possible for nine billion people to have the lifestyle enjoyed today only by the wealthy? One school of thought says no: not only should the majority of the world's people resign themselves to poverty forever, but rich nations must also revert to simpler lifestyles in order to save the planet.

Admittedly, there may be political or social barriers to achieving a rich world. But in fact there seems to be no insuperable physical or ecological reason why nine billion people should not achieve a comfortable lifestyle, using technology only slightly more advanced than that which we now possess. In thinking about the future of civilization, we ought to start by asking w hat people want. The evidence demonstrates that as people get richer they w ant a greater range of personal technology, they want lots of room (preferably near or in natural surroundings) and they w ant greater speed in travel. More possessions, more space, more mobility.

In the developed world, the personal technologies of the wealthy, including telephones, washing machines and ears, have become necessities within a generation or two. Increasing productivity that results m decreasing costs for such goods has been responsible for the greatest gains in the standard of living, and there is every reason to believe that this will continue.

As affluence grows, the amount of energy and raw- materials used for production of machinery w ill therefore escalate. But this need not mean an end to the machine age. Rather than being throw n away, materials from old machinery can be recycled by manufacturers. And long before all fossil fuels are exhausted, their rising prices may compel industrial society not only to become more energy efficient but also to find alternative energy sources sufficient for the demands of an advanced technological civilization nuclear fission, nuclear fusion, solar energy, chemical photosynthesis, geothermal, biomass or some yet unknown source of energy.

The growth of cities and suburbs is often seen as a threat to the environment. However, in fact the increasing amount of land consumed by agriculture is a far greater danger than urban sprawl. Stopping the growth of farms is the best way to preserve many of the world's remaining wild areas. But is a dramatic downsizing of farmland possible? Thanks to the grow th of agricultural productivity, reforestation and ‘re-wilding’ has been under way in the industrial countries for generations. Since 1950 more land in the US has been set aside in parks than has been occupied by urban and suburban growth. And much of what was farmland in the nineteenth century is now forest again. Taking the best Iowa maize growers as the norm for world food productivity, it has been calculated that less than a tenth of present cropland could support a population of 10 billion.

In The Environment Game, a vision of a utopia that would be at once high-tech and environmentalist. Nigel Calder suggested that ‘nourishing but unpalatable primary food produced by industrial techniques - like yeast from petroleum may be fed to animals, so that we can continue to eat our customary meat, eggs. milk, butter, and cheese and so that people in underdeveloped countries can have adequate supplies of animal protein for the first time.'

In the long run. tissue-cloning techniques could be used to grow desired portions of meat by themselves. Once their DNA has been extracted to create cow less steaks and chicken less drumsticks, domesticated species of livestock, bred for millennia to be stupid or to have grotesquely enhanced traits, should be allowed to become extinct, except for a few specimens in zoos. However, game such as wild deer, rabbits and wild ducks w ill be ever more abundant as farms revert to wilderness, so this could supplement the laboratory-grown meat in the diets of tomorrow's affluent.

With rising personal incomes come rising expectations of mobility. This is another luxury of today’s rich that could become a necessity of tomorrow’s global population - particularly if its members choose to live widely dispersed in a post-agrarian wilderness. In his recent book Free Flight. James Fallows, a pilot as well as a writer, describes serious attempts by both state and private entrepreneurs in the USA to promote an ‘air taxi' system within the price range of today’s middle class and perhaps tomorrow’s global population.

Two of the chief obstacles to the science fiction fantasy of the personal plane or hover car are price and danger. While technological improvements are driving prices down, piloting an aircraft in three dimensions is still more difficult than driving a car in two. and pilot error causes more fatalities than driver error. But before long our aircraft and cars will be piloted by computers which arc never tired or stressed.

So perhaps there are some grounds for optimism when viewing the future of civilization. With the help of technology, and without putting serious strains on the global environment, possessions, space and mobility can be achieved for all the projected population of the world.

Space travel may still have a long way to go, but the notion of archaeological research and heritage management in space is already concerning scientists and environmentalists.

In 1993, University of Hawaii’s anthropologist Ben Finney, who for much of his career has studied the technology once used by Polynesians to colonize islands in the Pacific, suggested that it would not be premature to begin thinking about the archaeology of Russian and American aerospace sites on the Moon and Mars. Finney pointed out that just as todays scholars use archaeological records to investigate how Polynesians diverged culturally as they explored the Pacific, archaeologists will someday study off-Earth sites to trace the development of humans in space. He realized that it was unlikely anyone would be able to conduct fieldwork in the near future, but he was convinced that one day such work would be done.

There is a growing awareness, however, that it won’t be long before both corporate adventurers and space tourists reach the Moon and Mars. There is a wealth of important archaeological sites from the history of space exploration on the Moon and Mars and measures need to be taken to protect these sites. In addition to the threat from profit- seeking corporations, scholars cite other potentially destructive forces such as souvenir hunting and unmonitored scientific sampling, as has already occurred in explorations of remote polar regions. Already in 1999 one company was proposing a robotic lunar rover mission beginning at the site of Tranquility Base and rumbling across the Moon from one archaeological site to another, from the wreck of the Ranger S probe to Apollo 17 s landing site. The mission, which would leave vehicle tyre- marks all over some of the most famous sites on the Moon, was promoted as a form of theme-park entertainment.

According to the vaguely worded United Motions Outer Space Treaty of 1967. what it terms ‘space junk’ remains the property of the country that sent the craft or probe into space. But the treaty doesn’t explicitly address protection of sites like Tranquility Base, and equating the remains of human exploration of the heavens with ‘space junk’ leaves them vulnerable to scavengers. Another problem arises through other international treaties proclaiming that land in space cannot be owned by any country or individual. This presents some interesting dilemmas for the aspiring manager of extraterrestrial cultural resources. Does the US own Neil Armstrong's famous first footprints on the Moon but not the lunar dust in which they were recorded? Surely those footprints are as important in the story of human development as those left by hominids at Laetoli, Tanzania. But unlike the Laetoli prints, which have survived for 3.5 million years encased in cement-like ash. those at Tranquility Base could be swept away with a casual brush of a space tourist’s hand. To deal with problems like these, it may be time to look to innovative international administrative structures for the preservation of historic remains on the new frontier.

The Moon, with its wealth of sites, will surely be the first destination of archaeologists trained to work in space. But any young scholars hoping to claim the mantle of history’s first lunar archaeologist will be disappointed. That distinction is already taken.

On November 19. 1969. astronauts Charles Conrad and Alan Bean made a difficult manual landing of the Apollo 12 lunar module in the Moon’s Ocean of Storms, just a few hundred feet from an unmanned probe. Surveyor J. that had landed in a crater on April 19. 1967. Unrecognized at the time, this was an important moment in the history of science. Bean and Conrad were about to conduct the first archaeological studies on the Moon.

After the obligatory planting of the American flag and some geological sampling, Conrad and Bean made their way to Surveyor 3. They observed that the probe had bounced after touchdown and carefully photographed the impressions made by its footpads. The whole spacecraft was covered in dust, perhaps kicked up by the landing.

The astronaut-archaeologists carefully removed the probes television camera, remote sampling arm. and pieces of tubing. They bagged and labelled these artefacts, and stowed them on board their lunar module. On their return to Earth, they passed them on to the Daveson Space Center in Houston, Texas, and the Hughes Air and Space Corporation in bl Segundo, California. There, scientists analyzed the changes in these aerospace artefacts.

One result of the analysis astonished them. A fragment of the television camera revealed evidence of the bacteria Streptococcus mitis. I or a moment it was thought Conrad and Bean had discovered evidence for life on the Moon, but after further research the real explanation became apparent. While the camera was being installed in the probe prior to the launch, someone sneezed on it. The resulting bacteria had travelled to the Moon, remained in an alternating freezing.' boiling vacuum for more than two years, and returned promptly to life upon reaching the safety of a laboratory back on Earth.

The finding that not even the vastness of space can stop humans from spreading a sore throat was an unexpected spin-off. But the artefacts brought back by Rean and Conrad have a broader significance. Simple as they may seem, they provide the first example of extraterrestrial archaeology and perhaps more significant for the history of the discipline formational archaeology, the study of environmental and cultural forces upon the life history of human artefacts in space.