Aliens: once just a modern stand-in for the leprechauns and goblins of the past, our culture is now awash with them. Despite their use in popular fiction and the ramblings of conspiracy theorists, it's respectable - indeed inevitable - for modern science to accept the likelihood of their existence. But SETI is doomed to failure and the UFOlogists are clearly wrong, because if there truly is life out there, it's not going to look like anything on Earth - and we might not even be able to recognise it at life...
Ian Stewart and Jack Cohen are quite the double act. They refer to themselves in their co-authored books (and both have been published independently) as Jack&Ian, and their writing has a distinct style of its own. I was introduced to them via their association with Terry Pratchett, with whom they have written three volumes of The Science of Discworld, but ever since I saw the title What Does A Martian Look Like? in their list of previous works, I wanted to find and read it. It took a while; I'm not sure it's still in print. I eventually found it in that prince among warehouse bookstores, The Book Grocer. In the meantime though, I'd read Stewart's Flatterland, a sequel to Flatland which, among other things, contains one of my favourite explanations of string theory, and convinced me to pick up the large format Annotated Flatland for which he wrote the notes.
So there was quite a build up to reading What Does A Martian Look Like, and I have to say, it was a bit of a disappointment.
It's not a bad book, but I admit I'm baffled as to its intended audience. The Science of Discworld books are among the best popular science books I've read: they're accessible, written with great humour, they cover broad topics, where possible they relate them to everyday life of the reader, and they're as much about the idea and practice of science itself as they are about scientific subjects. This book has shades of all that, but more than anything else it reminds me of Darwin's Origin of Species - it goes to great length to explain and justify a position, so great in fact that it says the same thing many times over in different ways. This is all the stranger when their main point is very simple: aliens will not be like any life on Earth, and certainly not like any of the aliens we've imagined in fiction.
Early on they have some reason for a mounted attack on established knowledge; they justify throwing out most alien-based science fiction, and also explain how their concept of xenoscience is different from astrobiology of the sort practised by NASA. But the rest of the book seems to think it is struggling against a cemented notion in the head of the reader that aliens will look like humans with bumpy foreheads or giant anthropomorphic cats, or lizards, or beetles etc. But honestly, no-one willing to read a dense (the type is very small!) 350 page book about the scientific realities of alien life is going to believe that. The science in the book isn't all that basic, either; lots of concepts are introduced and explained (all with the authors' usual flair for analogy, it's true) in short order.
For me, who already felt this way - I get a bit annoyed when yet another sci-fi story talks about "alien DNA" or worse, splices it into our own (aliens will not have DNA, though they will probably have something that fulfils a similar function) - the whole exercise became a little tedious. I found myself thinking "Yes, I know they won't be like us, give me some more ideas of what they might be like!" Even the little bits of fiction that introduce each chapter are vague and fast, leaving little idea of what the tourist aliens cataloguing Earth-life are supposed to be like.
This is sounding very negative, which is disappointing because I've enjoyed Jack&Ian's other work so much. There are some interesting discussions of what forms life might take, though they justify their decision to give precious few examples by repeatedly stating that aliens will not look like anything they - or any human - can imagine. They do a good job of explaining where popular myths of aliens come from (the clue in that sentence is the word "myth"), and likewise their discussions of the problems with various ideas of aliens in fiction and the various bits of about the staggering variety of weird life on Earth are fascinating. But it was a bad sign, I think, when I was looking forward eagerly to their summaries of major works of science fiction more than their next point, included so they could be discussed with those who've not read them. (That said, this often led to a different kind of disappointment when a particularly interesting book, tantalisingly summarised, was included only so an off-hand reference could be made in a single paragraph.)
It was a long slog getting through What Does a Martian Look Like?, but it wasn't all bad. I am well-equipped to argue with people who believe in UFOs, or who think the X-Files was the most realistic portrayal of aliens on television. But here's a word to the wise: don't title a factual book with a question you have no intention of answering. I was really expecting some interesting case studies on what kind of life might exist in different bizarre environments, and that forms such a small part of the book that it would have been more honest to title it "Why Won't Aliens Be Like in the Movies?"