Davies then launches into a discussion about the factors - as unlikely and absurdly complex as they are - that created the conditions for life on Earth to begin. He says that:
'The question of whether or not we are alone in the universe is one of the great unsolved puzzles of science. The answer hinges on whether the origin of life was a stupendous chemical fluke that may have happened only once in the observable universe, or was the expected outcome of intrinsically bio-friendly laws that facilitate the emergence of life wherever Earth-like conditions prevail.'
I was pleased to read that Davies doesn't limit his thinking by assuming that the only kinds of possible life are ones that require 'Earth-like' conditions. But a lot of other authors do and, certainly, I've read any number of science reports in magazines and periodicals that promote the idea that life can only possibly exist where there is liquid water, an oxygen-rich atmosphere and a planetary temperature that is in the 'Goldilocks' zone; not too hot, not too cold - just right.
But as we've seen in recent years ... life is extremely hardy and not nearly so fragile as we once thought. At the bottom of the dark, cold, crushing sea are thermal vents; so-called 'black smokers' where life clusters and proliferates, deriving all of its energy from chemical reactions rather than sunlight. And we have found 'extremophiles'; hardy organisms that can survive in the freezing vacuum of space or in the fiery pools and rocks that surround volcanic activity. And these are just some of the organisms we identify as 'living'. But what if we're wrong (as we have been about so many other things in the past)? What if the definition of 'life' that we use is too limiting?
I spent some time today thinking about forms of life that maybe don't need any of the things that some people believe are essentials. And I found myself following a train of thought that led me past various energy life-forms in sci-fi novels and TV shows to an old friend from the 1970s and early 80s that I'd quite forgotten about - Pac-Man. I was 18 years old when Namco released the first Pac-Man video game in 1979 and I can remember queueing with my friends to have a go on the first arcade machine to arrive in our town. And I can remember being fascinated by the fact that the ghosts seemed able to anticipate where I would send the little yellow chomping ball. The fact that I was so crap at playing the game (a skill I haven't lost in any video game since) even hinted at me that the electronic organisms on the screen were smarter than me; they could out-think my movements.
Ah, nostalgia! But with nostalgia came a question ... could we say, in any way, that electronic organisms like Pac-Man are actually alive?There is no one single definition for 'life' or 'living'. Wikipedia lists seven conventional factors that scientists use to distinguish life from non-life. They are:
- Homeostasis: Regulation of the internal environment to maintain a constant state; for example, sweating to reduce temperature.
- Organisation: Being composed of one or more cells, which are the basic units of life.
- Metabolism: Consumption of energy by converting non-living material into cellular components (anabolism) and decomposing organic matter (catabolism). Living things require energy to maintain internal organisation (homeostasis) and to produce the other phenomena associated with life.
- Growth: Maintenance of a higher rate of synthesis than catalysis. A growing organism increases in size in all of its parts, rather than simply accumulating matter. The particular species begins to multiply and expand as the evolution continues to flourish.
- Adaptation: The ability to change over a period of time in response to the environment. This ability is fundamental to the process of evolution and is determined by the organism's heredity as well as the composition of metabolised substances, and external factors present.
- Response to stimuli: A response can take many forms, from the contraction of a unicellular organism when touched to complex reactions involving all the senses of higher animals. A response is often expressed by motion, for example, the leaves of a plant turning toward the sun or an animal chasing its prey.
- Reproduction: The ability to produce new organisms. Reproduction can be the division of one cell to form two new cells. Usually the term is applied to the production of a new individual (either asexually, from a single parent organism, or sexually, from at least two differing parent organisms), although strictly speaking it also describes the production of new cells in the process of growth.
These seven factors are controlled by our DNA; a set of coded instructions from which all designs for life are derived (except those few organisms that use RNA instead). DNA contains all of the instructions that make us work, whether we are a mushroom, a used-car seller or a wombat. The electronic world's equivalent of DNA is the programme; a set of coded instructions that instruct the electronic organism how to look and behave. The more complex the programme, the more independent the electronic organism can be. Consequently, advanced computer organisms or sprites can perform all of the tasks that living organisms can.
Just as very simple organisms like amoebas or bacteria have very simple reactions (mostly stimulus-response), so too does Pac-Man. And with a tweak to his coding he could be made to reproduce, either by cloning his electronic 'body' or by getting jiggy with Ms Pac-Man. He has a form of metabolism, deriving nourishment from power pills and even extending his life by chomping ghosts (with which he enjoys a classic predator-prey relationship). Again, another tweak in the programme would allow the expulsion of waste, homeostasis and for growth to occur as he takes on more nourishment and grows older. He even has cells of a kind in the form of pixels. And, just like life as we know it, he dies when ghosts kill him, he runs out of nourishment or the fluid medium that allows all actions to happen in his 'body' (in our case water, in his electricity) is witheld. With sufficiently complex coding, he could even adapt to his environment and evolve.
Back in 2003, researchers at Michigan State University created populations of identical 'digital organisms', using a computer modelling application called Avida. At the start, each digital organism was incapable of solving logical problems. But with each replication, there was a 20% chance of a random mutation in their 'offspring'. This mutation altered the nature of the digital organism and in some cases resulted in one that could perform a logical operation. In this experiment, the electronic organisms could be said to have evolved.So in all senses, Pac-Man could technically be said to be alive, as long as the programme that controls him is sufficiently complex. Programmes don't come much more complex than DNA, so if Pac-Man's coding was just as complex, would he achieve sentience? This is a question that developers of artificial intelligence are already asking themselves. At what point will their creations become artificial life?
Back around the time when Pac-Man was new, Christopher Langton, a long-time advocate of using computers to simulate life, first defined 'Artificial Life' like this:
'Artificial life is the study of artificial systems that exhibit behaviour characteristic of natural living systems. It is the quest to explain life in any of its possible manifestations, without restriction to the particular examples that have evolved on earth. This includes biological and chemical experiments, computer simulations, and purely theoretical endeavours. Processes occurring on molecular, social, and evolutionary scales are subject to investigation. The ultimate goal is to extract the logical form of living systems.'
Microelectronic technology and genetic engineering will soon give us the capability to create new life forms in silico as well as in vitro, This capacity will present humanity with the most far-reaching technical, theoretical and ethical challenges it has ever confronted. The time seems appropriate for a gathering of those involved in attempts to simulate or synthesise aspects of living systems.'
So, if artificial non-cellular life forms could one day be manufactured in a lab, could they evolve naturally? Could there be a real Pac-Man out there? Could life forms have evolved in places where the conditions are such that electrical beings could flourish?
Interestingly, in the same year that Michigan State University was creating its digital organisms, scientists at Cuza University in Romania were creating blobs of gaseous plasma that could grow, replicate and communicate - fulfilling most of the traditional requirements for biological cells. Without inherited material they could not be described as 'alive' (as we currently categorise life), but the researchers believed that these curious spheres may offer a radical new explanation for how life began. As reported in New Scientist magazine at the time:
'The researchers studied environmental conditions similar to those that existed on the Earth before life began, when the planet was enveloped in electric storms that caused ionised gases called plasmas to form in the atmosphere. They inserted two electrodes into a chamber containing a low-temperature plasma of argon - a gas in which some of the atoms have been split into electrons and charged ions. They applied a high voltage to the electrodes, producing an arc of energy that flew across the gap between them, like a miniature lightning strike. Dr Mircea Sanduloviciu says this electric spark caused a high concentration of ions and electrons to accumulate at the positively charged electrode, which spontaneously formed spheres. Each sphere had a boundary made up of two layers - an outer layer of negatively charged electrons and an inner layer of positively charged ions. Trapped inside the boundary was an inner nucleus of gas atoms. The amount of energy in the initial spark governed their size and lifespan. Sanduloviciu grew spheres from a few micrometres up to three centimetres in diameter.'
A distinct boundary layer that confines and separates an object from its environment is one of the four main criteria generally used to define living cells. Sanduloviciu decided to find out if his cells met the other criteria: the ability to replicate, to communicate information, and to metabolise and grow. He found that the spheres could replicate by splitting into two. Under the right conditions they also got bigger, taking up neutral argon atoms and splitting them into ions and electrons to replenish their boundary layers. Finally, they could communicate information by emitting electromagnetic energy, making the atoms within other spheres vibrate at a particular frequency. The spheres are not the only self-organising systems to meet all of these requirements. But they are the first gaseous 'cells'. But perhaps the most intriguing implications of Sanduloviciu's work are for life on other planets. 'The cell-like spheres we describe could be at the origin of other forms of life we have not yet considered,' he says. Which means our search for extraterrestrial life may need a drastic re-think. '
So there you go - life as plasma spheres emitting and being fed by electromagnetic energy. Fascinating prospect isn't it? Suddenly Pac-Man doesn't look so outlandish.I must add one final note (I couldn't resist it) before we leave the world of Pac-Man behind us. Back in 2002, in an entirely different twist to the 'Pac-Man as a living organism' discussion, French artist Le Gentil Garçon got together with palaeontologist François Escuilié to create a fossil Pac-Man skull. They approached the project in a purely scientific way and, by studying the character's life-style, determined that Pac-Man was a predator and designed the skull accordingly. Fabulous.
Oh, and in case you've ever wondered why the character is called 'Pac-Man', it's a corruption of the Japanese onomatopoeic phrase 'Paku-paku' which represents the sound of rapidly chomping jaws. The game's designer, Toru Iwatani, originally called the character 'Paku-Man'.
New Scientist, Le Gentil Garcon, Wikipedia
The Goldilocks Enigma by Paul Davies (ISBN-10: 0141023260, ISBN-13: 978-0141023267
Parallel Worlds by Michio Kaku (ISBN-10: 0141014636, ISBN-13: 978-0141014630)
This feature first appeared on my now defunct Worlds of Possibility Blog