Why aliens will be like us
Science fiction film-makers love to dream up all sorts of scary looking aliens to help boys get their dates clutching them but when one looks at the science end of science fiction process of elimination suggests that aliens will look surprisingly like ..well..us.
A putative alien has to achieve a number of important evolutionary steps in order to be in a position to achieve at least our level of civilisation. We don’t really know if we are up to achieve more but we can already see challenges to our own species even as we have come to dominate the planet we live on.
Inevitably we have to start from some level of basic chemistry. This page on Wikipedia traverses the issues with more authority than I can muster: http://en.wikipedia.org/wiki/Alternative_biochemistry . However it essentially makes fairly plain that Life, as we know it, based on water carbon and oxygen is the most likely evolutionary combination. Given the reliance on water we therefore have to accept the Goldilocks Zone hypothesis which requires that the planet our aliens start on is not too hot and not too cold for liquid water. I would also suggest that the planet can’t be too small (with reduced gravity) or too large (with heavy gravity) because of the effect that would have on water. The growing realisation that the lithosphere has an important role in the composition of the atmosphere and the importance of subduction zones suggests too that any alien planet will experience tectonic drift and limited volcanism.
As with Earth the crucial stage in the evolution of the planet must be the release of oxygen into the atmosphere. Without oxygen life will remain limited to plants and anarobic microbes. Only oxidisation offers the energy potential necessary for animal life to develop. In other words aliens from other worlds are unlikely to be gasping for ammonia but are probably oxygen breathers just as we are.
To develop a civilisation an alien has to be bright. Lumping around roaring and gnashing large teeth is out. An intelligent alien will need a decent sized brain capable of abstract thought. But while a brain is important it is not the only thing. Humans do not have the largest brains on our planet Sperm whales do. That said intelligence may not be a function of brain size. Birds are surprisingly intelligent for creatures with relatively small brains. It is notable that the evolutionary forcing of human kind is due to the fact that as a species we came very close to extinction. DNA variability in the entire human race (6 billion) is less than that of our nearest relatives (chimps), suggesting that as a species we were cruelly selected for intelligence early in our evolution. Some studies suggest we are all descended from no more than 1,000 individuals.
Size is important. Elephants and Sperm Whales are intelligent creatures. But they are also so much larger than competing life forms that their intelligence is more of a bonus than anything else. Unlike us they don’t need to make weapons for survival, they can muscle their way through in a way we cannot. Teeth and horns are also important. We don’t have any. If we did we wouldn’t need to make weapons. If aliens have teeth or horns they won’t be very important. So the prospect for civilised T-Rex’s is pretty slim.
It is obviously essential that an alien intelligence must be able to manipulate objects in its environment and use tools. Elephants, chimps and even octopuses are capable of this. An alien will therefore need some form of hand. It is notable that both the elephant’s trunk and the octopuses arms are not really capable of very fine operations such as threading a needle. If one examines a chimps “hand” it is actually more like a foot while its feet are more like hands. This is a drawback for fine work although chimp termite fishing is relatively delicate. Thus manipulation will require fingers or sub-tentacles of some kind.
Can intelligent aliens be aquatic? The only animal that fits the bill so far would be an Octopus. But there are two important drawbacks for aquatic life. One is the power of aquatic currents and the inability to set mud or cement underwater would make primitive construction problematic, but more importantly is the fact that fire and water don’t mix. The ability to use fire is a crucial stage in our evolution as an intelligent species. We used it for chemical processes (cooking and manufacture of glass and metals), hunting, defence against night-time predators, and of course coping with changing seasons and climates. Fire was a crucial step in our journey to dominating our environment and it is simply not available under water or in atmospheres where oxidisation is impossible.
Having established that our aliens are land animals what will they look like. Many science fiction producers like to suggest aliens with multiple limbs. Nature played with multiple limbs some time ago but the fact is four is a very good number. Most four legged ground creatures move at top speed by leaping from their back legs on to their front legs, bringing up their back legs and leaping again. Power comes not only from the rear legs but also from the entire abdomen. Adding more legs, like an insect, reduces the efficiency of movement rather than adding to it. A large six or eight legged creature would be easy meat for more efficient four legged creatures, as indeed nature proves as spiders simply don’t get much larger than a large mouse and those that do have to worry about aggressive mammals.The only important exception to this is the Kangaroo which uses its tail as a limb very effectively. That said for aliens to be intelligent they will have to experience evolutionary forcing and so won’t be capable of running as fast as a kangaroo. So our aliens will have two legs, possibly a tail, and at least two arms with something like hands.
Will they have heads? While a head seems a rather vulnerable structure it is obviously built to shorten the distance between the creatures visual, orlfactory and auditory sensors and its processor. Even snails have heads. Why do this? Obviously to minimise the reaction time between senses and processing. A creature that loses a second or two making sense of its perceptions while another is attacking it will be rapidly tossed out of the evolutionary tree. Aliens will have heads, with mouths and eyes. Interestingly they will also need stereoscopic vision particularly for fine manufacture.
Will aliens be furry like Chewbacca the Wookie? Unfortunately we are not entirely sure why humans are not furry. Elaine Morgan’s Aquatic Ape hypothesis is probably the best suggestion available: namely that we owe our survival and early development to a retreat into water at some point as we are the only ape that seeks out the water to swim in and derives a significant amount of food from. Is this essential to all intelligences? On the face of it there is no logical reason to think so, on the other hand humankind’s nakedness is associated with some fairly important drivers toward civilisation. These drivers include: the ability to respond to climate change through predation and fire and the technical discovery of weaving and cloth which might be ignored if clothes were unnecessary.
This raises a rather sensitive and important point and that is response to temperature and climate variability. The simple fact is that not all homo sapiens – even today – are civilised. In some parts of the world there are still people living as homo sapiens did 10,000 years ago. Why? Because they have not needed to respond to the threat of cold weather. It would be entirely possible to have a planet full of Papuan Highlander Aliens happily enjoying life without civilisation simply because they had never had to deal with the challenges of cold weather. That said there is challenge and there is extermination. Too much cold and photosynthesis stops. If that happens its all over Rover. So civilisation needs some cold but not so much that it kills all life on a planet.
As an aside it often amuses me to see Science Fiction Writers suggest planets that are totally urbanised. Such a planet would die in short order from atmospheric collapse. I suspect such writers don’t get out much and over impressed by their tiny urban environments have no idea how large their own planet actually is.
So far I have hinted at, but not established that Aliens will be predators. Animals that live on grass and browse do not tend towards intelligence because their food is very easy to catch. To avoid predators they either develop speed, high breeding rates or armour or size. Gorillas are our closest pure vegetarian relative and while highly intelligent, like elephants their relative size precludes them from developing hunters intelligence. Chimps which are meat eaters are sharper customers. The other reason is that predators enjoy far greater energy density from their food. Plant eaters have concentrated all that plant energy for them. This makes predators more efficient than non-predators. So aliens will have eaten meat at some point although like us they won’t be originally evolved to do (ie equipped with fangs and claws).
One of the great chauvenisms expressed by science fiction writers is that aliens won’t understand love. This is arrant tosh. Aliens have to understand love because like us they will have long childhoods. The reason they will have long childhoods is that they will have a lot to learn. Animals that don’t recognise their offspring (ie they eat them) rely entirely on instinct. Animals that are devoted to their offspring can educate them. Without the patience engendered by love an alien civilisation would have no chance. It is notable that over time civilisations have become gentler not harsher. In Ancient times making a pyrimad of the skins of your enemies was fairly harsh but not unknown. By contrast even the Nazis were troubled by rendering Jews into lampshades. While the history of human conflict is marked by some fairly apalling acts overall civilisation has increased caring not reduced it. A more advanced civilisation is therefore more likely to be more benevolent than our own.
Aliens are also likely to be more subtle communicators. Human history has seen an explosion in the number and range of words exchanged, used and understood. From the grunts of cavemen to the thoughts of Bhudda or Aristotle to the poetry of Shakespeare the scope for thought has simply expanded as civilisation has globalised. Aliens are likely to consider us fairly primitive in word and speech.
And one final thing that Aliens will have to have solved that we haven’t is the ability to develop a sustainable civilisation. Aliens will have to have balanced their own population, their agriculture and their ethics in a way that we are merely fumbling toward.
That at least will be the alien life forms
What their robots will be like one can scarcely guess.
