A GUT of ecological scaling?

OK. I'm not going to pretend that I grasp the details of this, but here goes.

A recent paper in Physical Review Letters by Jayanth Banavar et al. presents a general theory of (macro)ecological scaling.

That is, they offer a common explanation for patterns such as that between the area of a place and the numbers of species that live there, area and total biomass, the number of organisms and species of different sizes, the maximum body size of the biggest species in an ecosystem (see here for another view of maximum carnivore size), and relative abundance — the spread of rare and common species.

All these scaling patterns seem to follow power laws, at least over partially. That is, they take the form y=ax^n, and plot as straight lines on a log/log graph.

Here's the abstract:

Scaling provides an elegant framework for understanding power-law behavior and deducing relationships between critical exponents. We demonstrate that scaling theory can be generalized to develop a framework for the analysis of diverse empirical macroecological relationships traditionally treated as independent. Our mathematical arguments predict links between the species-area relationship, the relative species abundance and community size spectra in excellent accord with empirical data.

As far as I can tell, Banavar et al. present a scaling hypothesis, based on a probability distribution of the mass and abundance of different species. Using this, and a set of reasonable assumptions (such as, that an ecosystem's total population and mass is proportional to its area) they derive the relationships described from a single starting point.

Blimey. If all these things can be brought under the one roof — this is the first such attempt that I know of — that's a big deal, I think. These are fundamental ecological parameters. Together, they pretty much sum up most of the questions that community ecology seeks to answer. Even the metabolic ecology models of West et al. (with which I am more familiar) have steered clear of tackling the relationships between species diversity and area, and between body size and diversity and abundance.

But, although much of the criticism of metabolic ecology focuses on its generality, Banavar and his colleagues have an interesting history of seeking yet more general models for the scaling of metabolic rate with body size. Banavar has also worked with Steve Hubbell to develop the neutral ecological theory. It's interesting that this is in PRL. I wonder what a biology journal would have made of it.

Thanks to Phil Ball for bringing this to my attention. I think. If anyone has any thoughts on this, I'd love to hear them.

Oekologie blog carnival

Just a reminder that this blog will be hosting next month's round of the Oekologie blog carnival. This follows the grand jobs done so for by Infinite Sphere and Perceiving Wholes.

So, for the period of Feb 15-March 14, please send me your favourite ecological and environmental blog posts by following this link. And I'll bring it to the world's attention, or at least that subsection of the world that reads this.

Review: Measuring the world

I'm still recovering from the Just-Science exertions of last week, but I have got a review of Daniel Kehlmann's Measuring the World in this week's Nature ($).

They asked me to do this because I write a bit about one of the book's central characters, Alexander von Humboldt, in ITBOAH.

As a rule, I'm not really into historical fiction, or magic realism/postmodern whimsy. But I rather liked MTW (which has been a huge success in German). And I liked it more as it went along.

If you'll forgive me for quoting myself:

Kehlmann tells his story in a relentless deadpan, which is at first alienating but then gets under the skin. As the story develops, your sympathy for the two men grows, as their own does for each other. [He] does a good job of capturing the strangeness and comedy of science, as well as the powerful sense of futility that can afflict researchers from time to time.

Just Science day 5: Kill and cure?

The best way to protect an endangered species might be to ... cull it.

That's the conclusion reached by Michael Bode and Hugh Possingham in a theoretical analysis published recently in Ecological Modelling. The problem that they address is the tendency of some species to show boom-and-bust population dynamics. This seems a particular feature of tightly linked predator-prey systems: if predator is rare, prey booms, predator has lots of food, predator booms, prey crashes, predator starves, predator crashes, and so on. The Canadian lynx-hare system is the most famous example.

At the bottom of the cycles, population sizes might be so small that either predator or prey is highly vulnerable to extinction - by some other event, such as disease or disaster.

Bode and Possingham model various options for damping these cycles by removing some predators, prey, or both, from the system. "Remarkably," they say, "if the interventions are enacted at the appropriate time, infrequent culling of a small number of individuals significantly reduces the probability of extinction of the predator."

My first thought when I saw this, was that we probably rarely know enough about a species' population dynamics to know when the best time to cull is, and that such a move would be politically untenable. But, as Bode points out, the most likely candidates for such a move are large game-park species, such as elephants, about which we know quite a lot. It's also heartening that their (as they say, simplistic) simulation suggests that culling prey (which would be plants for elephants, I suppose) is more likely to be effective than predators, and that culling would be needed only rarely.

They conclude:

Most current methods of ecosystem control attempt to keep a single species population below a certain threshold, or between fixed bounds, leading to highly inefficient management. Furthermore, unnecessarily high levels of culling can generate considerable public opposition. Given the clumsy nature of such static controls, this view may be reasonable. Our dynamic control solution has the substantial benefit of minimising the preventable culling of organisms, and being extremely cost-effective.

I swapped e-mails with Bode, and besides mentioning that, in parks with very high elephant densities, such as Kruger, culling elephants seems 'almost unavoidable' (the issue seems to have flared up most recently in late 2005, judging by this BBC story), he also mentioned that similar issues were arising in Australia regarding koalas and kangaroos. As he says, why is it always the cure animals?

All I can say is I'm glad I don't have to make these decisions. Culling animals is clearly a terrible business - particularly for long-lived, highly social species such as elephants. But we now effectively control the destiny of all large, slow-breeding vertebrates. If the only places they can survive is in the parks we set up, and if we take a truly utilitarian and, dread word, holistic view of conservation, then we also have to take the responsibility of 'managing' their populations. Science isn't he only thing to guide us on such decisions, but it's best ot take as informed and clever a decision as possible, towards which Bode and Possingham's ideas can only help.

Just Science day 4: Cursory

What's (even) more fun than blogging? Snow!

So, if you'll excuse me, I'm going to recommend that you check out this paper on potential pitfalls of digital photography in biology, and this article by the excellent Jenny Diski, providing a much-needed antidote to all the gush concerning Second Life.

And now I'm off to muck about on Hampstead Heath.

Just Science day 3: The H. pylori story

A new Nature paper by Mark Achtman and his colleagues reminds me that today, Helicobacter pylori (Hp) is definitely my favourite member of the human gut flora.

This bacterium is best known for causing ulcers and increasing the risk of stomach cancer. Barry Marshall and Robin Warren won a Nobel prize in 2005 for showing this (famously, few believed that bacteria could survive in the concentrated acid of the stomach, but Marshall chugged down a load of Hp, and got an ulcer.)

But the bacterium is much more than just a baddie. Once upon a time, it was probably in everybody's tummy (although no one is quite sure how its transmitted — vomit seems like the most likely culprit). It's still very common in developing countries and east Asia, but in Europe and North America it's steadily declined — only about 20% of US residents under 40 have it.

A good thing, you might think. But some scientists, such as Martin Blaser, have suggested that there might be a cost to this decline, as well as the benefit of reduced ulcers. Hp reduces the level of stomach acid, so without it there seems to be more heartburn, and possibly an increased risk of oesophageal cancer. There's also the general unknown consequences of having a part of the human ecosystem go extinct: "We have no good sense of the microbial ecology of humans," says infectious-disease specialist Julie Parsonnet of Stanford University in California. "H. pylori infection revs up the immune system - what happens to our ability to respond to other infectious agents when that isn't there?"

Another thing people have argued about is how the bug got into us in the first place:

Most mammals seem to have their own species of Helicobacter in their stomachs, leading some researchers to suggest that the relationship between microbe and host predates the evolution of modern humans. But others think that H. pylori's hook-up with humans, and subsequent spread around the world, was more recent.

That's the view taken by geneticist Douglas Berg of Washington University in St Louis, Missouri. Berg and his colleagues looked at more than 500 strains of the bacterium taken from people in five continents. Native Peruvians had bacteria more similar to Spaniards, they found, even though their genes are more similar to those of East Asians - the group that settled the Americas about 12,000 years ago. This led Berg and his colleagues to suggest that the conquistadors may have carried the bacterium to South America about 500 years ago, and that the continent's first humans arrived with virgin stomachs.

Martin Blaser disagrees. A microbiologist at New York University, he believes that Helicobacter has long been part of the gut flora of all humans. Late last year, Blaser and his colleagues seemed to reaffirm the ancient origins of American H. pylori, when they discovered strains closely related to the East Asian version of the bacterium in native people living in remote regions of Amazonia. And in unpublished work, pathologist Marvin Allison of the Medical College of Virginia in Richmond has detected H. pylori in the stomachs of 1,800-year-old Chilean mummies. In areas where Europeans and Amerindians had mixed, Blaser believes, indigenous strains have fallen victim to microbial imperialism.

The new study seems to confirm that Hp has an ancient origin. Achtman's team had previously shown that the spread of different Hp populations in stomachs around the world reflect the patterns of human migration. Now, they have found that we and them match up on a global scale:

[G]enetic diversity in H. pylori decreases with geographic distance from east Africa, the cradle of modern humans. We also observe similar clines of genetic isolation by distance (IBD) for both H. pylori and its human host at a worldwide scale.

So basically, we've been carrying it since we were human. Achtman has this graphic showing how the two spread:



Those of you with Nature subscriptions can read a 2003 feature by me on all this (which is where the earlier quotes came from). And if anyone's looking to write a short, sharp popsci book, you could worse than tell the H. pylori story. Just remember to give me a cut of the royalties.

Just Science day 2: They're only after one thing

Before we begin, I notice that the aggregator at Just Science has given yesterday's post the date of 31 December 1969. Can anyone help with why this has happened, and how to stop it happening again?

Anyway, on with the madness. With Valentine’s day just a week away, this paper in the new issue of Ethology is a must-read. In it, self-proclaimed ‘media friendly expert’, Karim Vahed, of the University of Derby, looks at nuptial gifts — the tasty morsels that many male animals (especially insects and spiders) bring to their intended mates.

The orthodox view of this is that everyone wins — the female gains a meal that increases her fertility, the male gets a mating. Vahed, however, has a rather more cynical take on things:

In this review, I explore the proposition that nuptial gifts act as sensory traps: by exploiting the female's gustatory responses, the male may be able to entice females to accept superfluous matings and/or transfer greater volumes of ejaculate than are in the female's reproductive interests.

Gift composition is more likely to be tailored to increasing the attractiveness of the gift to the female and/or maximizing gift handling time than to suit the female's nutritional needs … evidence suggests that the gift enables the male to overcome the resistance of the female to accepting an extra large ejaculate.

There is some evidence for this notion. Experiments in the fly Rhamphomyia sulcata suggest that females are almost as enthusiastic about worthless gifts as they are about a full dinner. Such indiscrimate behaviour leaves the door open to an invasion of cheating males.

And if Dr Vahed gives you a box of chocolates next Wednesday, beware.

Just Science day 1: cave bugs and shoot-em-ups

Not much time today (or tomorrow), so just a quick one drawing attention the juiciest morsels that popped into my inbox this morning.

First, and most closely related to this blog’s core themes, we have an interesting paper in Micobial Ecology by Raina Maier and her colleagues looking at the impact of tourists on the bacteria living in Kartchner Caverns, AZ.

These caves were opened to tourists in 1999. With admirable foresight (it’s depressing how rare this kind of thing is), researchers surveyed the caves’ microbial biota before opening, and now they reveal what’s changed as a consequence of having 200,000 people pass through the caves each year.

Raina's team found that the most heavily used areas had higher diversity, and different community composition — more Proteobacteria, fewer Firmicutes. This is probably a mixture of people bringing in bugs, and an increase in organic matter in the caves, say the researchers.

What we don’t know is what these changes mean for, say, nutrient cycling, food webs and so on in the caves, and whether they are something that should be of conservation concern. Microbial conservation is something I’d like to know more about, so if anyone has any pointers, please point them.

Three other things caught my eye:
1. Technological Forecasting and Social Change has a special issue of interesting-looking articles on terrorism and technology.

2. The Journal of Experimental Psychology reports that ‘action gaming enhances visuospatial attention throughout the visual field’ – i.e. playing Halo and its ilk makes you sharper-eyed. Whether this does you any good, and whether you get worse at anything else (insert your own joke about leaving the house, talking to girls etc.), is another matter.

3. And Psychopharmacology (always a favourite) finds that people who drink more coffee get more of a kick out of it. Which, given habituation and everything, seems to be the wrong way around. But I can’t tell from this abstract whether this is a consequence or cause of drinking lots and lots of lovely coffee.

There. That wasn't too bad. Back tomorrow.

Any other business

El Gentraso has rashly signed up to participate in Just Science. That means there'll be something new and science-related every day here Monday through Friday next week.

Equally rashly, I'll be hosting the March edition of Oekologie, the new ecology blogging carnival. It'll be just like real carnival, except without the samba bands and cross-dressing.

Meanwhile, in the real world, I'm speaking at the Edinburgh Science Festival on 9 April (easter Monday), talking about ITBOAH at 6 p.m. in the National Museum of Scotland's Lecture Theatre. And on 18 April I'm speaking about D'Arcy Wentworth Thompson at the Royal Institution in London. Except it'll be in the Royal College of Surgeons, because the RI's building is being done up. This is part of a series of RI events on polymaths.

Sleep and metabolic rate

Update: the link to the paper is now working. Duh. Sorry.

Sleep is another of those biological phenomena of which we lack a good theoretical understanding, despite there being lots and lots of (good) hypotheses and experiments. Van Savage and Geoff West have suggested a first step to building one, though. And (wouldn't you know it) it's based around metabolic rate.

The amount of time a mammal spends asleep, they find, is proportional to their relative, or cellular, metabolic rate. A fast-burner like a mouse sleeps for about 14 hours a day, whereas an elephant kips for only 3.5 hours. What's cool is that they find that sleep time is most closely matched to the brain's metabolic rate. Their suggestion is that sleep duration corresponds to the amount of time needed either repair brain cells, or reorganize them to process the day's input.

So unlike other organs, perhaps you need to shut down the (conscious) brain to maintain it. Fast-celled animals need more time for repairs (which, if this model holds, seems a more likely function of sleep - or at least of metabolically related sleep - than reorganization), because they do more damage while they're awake. The same argument applies to why small animals have shorter lifespans - fast cells, more free-radical damage, shorter lives.

What's that Lassie? A lot in life seems to depend on metabolic rate? Perhaps by understanding metabolic rate we can inch towards some kind of powerful, simple theory to explain a wide range of biology? You wish someone had written an accessible guide to this vibrant field and its long and strange history? Well, girl, it's your lucky day.

My new £16,000 habit

Winter finally came to London today, with a couple of inches of snow falling overnight. It was a nice surprise to wake up to. And not before time: we were hiking in the Peak District over new year, and you barely needed a coat, it was so warm (although the waterproof properties of goretex did come in handy, I admit). Woodland birds were singing, the odd tree was in blossom, and a friend in London has seen bumble bees in her garden. Anyway, enjoy the winter walking before the flood waters rise to engulf us all.

While in Derbyshire, we happened upon the excellent Hawkridge books in Castleton. They have a huge collection nature books, especially ornithology, and also good sections on climbing, mountaineering, etc.

In particular, they major in the Collin's New Naturalist series. This was set up during the second world war by, among others, Julian Huxley (who also popularized the use of allometry, thus earning himself a cameo in ITBOAH), with the intention of educating laypeople about the natural world.

Recently, the books have become collectors' items. The 100th in the series, 'Woodlands' by the legendary Oliver Rackham was published recently. There have also been other off-series monographs, so a complete set numbers around 120 books. The extremely nice man at Hawkridge told us that a set recently went at auction for £16,000 (about $32,000). The Woodlands book also exists in a limited edition, leather-bound version that is already changing hands for hundreds of pounds, apparently. The two rarest, nos. 70 Orkney and 71 Warblers (both from 1985) thanks to their extremely short print runs, are worth thousands. There's an extremely nice article about the whole thing here.

The NN clearly owe their value to a perfect storm of British male nerdiness - we, and especially amateur naturalists, love collecting, making lists, getting the complete set. So something that appeals to both naturalists and book collectors is bound to do well. They are also lovely books, with instantly recognizable covers.

Anyway,I'm not given to impulse purchases (although I'm quite partial to Nonesuch Explorer recordings on vinyl), but Hawkridge had a first edition of NN number 3, London's Natural History by Richard Fitter (with pictures by Eric Hosking, published in 1945 that they were selling for only £8. As a Londonist, this was clearly too good to miss, even though I had to carry it for several more days' walking. Only 102 (they're up to 103 now) to go.

How many pictures of leopards does the world need?

We went to the (staggeringly busy) Natural History Museum on Sunday, to see the Wildlife Photographer of the year exhibition. I've been coming to this for 20 years or more now. Usually I ooh and aah at the lovely pictures, and go away saying to myself it's a wonderful world. But this year, for some reason, I didn't react like that (or anyway, not just like that).

Here then, in no particular order, is the case against wildlife photography — or at least the vision of the natural world presented by this competition — that I found myself making as I walked round the show:

The same things seem to come back year after year — comical penguins, majestic birds of prey, big cats, cute baby animals. All set against atmospheric backdrops of sunsets, sunrises, snow, clouds of dust, and so on. It's a fine line between naff and beautiful.

Interestingly, the pictures that win the big prize tend not to be like this — more often, they are impressionistic (which I don't like, because they seem to be trying to imitate painting, which misses the point) or abstract, such as this year's winner, of a walrus, or last year's (which I think is an exciting and original image), of a peregrine attacking some starlings.

Does, and can, wildlife photography develop and change — like, say, portrait photography does. Obviously equipment gets better, but do the genre's aesthetics develop? Not much, would be my suspicion. There seems to be a very narrow version of what's beautiful and impressive about wildlife, that doesn't have a place for anything scary, or horrific (does anyone photograph parasitoids eating their way out of caterpillars?), or strange. Yet, let's face it, nature can be all of these things, and they are meat and drink to other forms of visual art.

The feeling that nature was being boiled down to a series of money shots also came to me while watching the BBC's Planet Earth series which, although it had some staggering images, and showed me lots of stuff I never new existed, lacked the narrative and scientific integrity of David Attenborough's various 'Life' series. Basically, the message was: 'Look at that! And that!'

(If Planet Earth was anything to go by, one thing that has changed in wildlife TV is that filmmakers are much less keen to show the violence that's often thought to be a staple of the genre — usually, the hunt was shown, but we cut off to somewhere else before the kill. This is probably a mixture of Good Taste, and a sense that this sort of thing is getting clichéd. Similarly, in the still photos there was no blood, or shagging.)

Such a highlights-reel approach commodifies nature. These photos blend seamlessly into the high-gloss adverts that surround and tempt us, and a lot of these pictures wouldn't have looked out of place in Condé Nast Traveller, say, or an advert for wide-screen television.

It also exoticizes nature, making it something that happens elsewhere. There's a category for urban wildlife, but it's weak, and this year's winning photo was of that noted urban species, the grizzly bear, pictured on that noted metropolis, the Kamchatka Peninsula. The risk is that we'll think of wildlife as something glossy, impressive, and expensive, not as all the stuff that surrounds us, and is worth checking out and looking after.

You can't blame photographers and exhibitors for this — folks wouldn't queue up to look at a whole roomful of pictures of starlings. But I would applaud the wildlife photographer who actually tried to capture the real experience of watching wildlife, rather than an idealized freeze-frame of wildlife. Usually, this involves a brief glimpse of something's arse as it scuttles into the undergrowth, or squinting at a distant silhouette. But such views are much more satisfying, because they're real, and because we have got them ourselves. Where's the Martin Parr of wildlife photos?

Feed the trees

How good are forests at soaking up carbon, and how much will they buffer greenhouse gas emissions and save us from climate change?

It's an extremely knotty question — and so this review (open access) of the issue just published in New Phytologist is extremely welcome. Increased CO2 should be a fertilizer, and things grow quicker in warm weather, but as temperature increases, the rate of respiration rises more quickly than the rate of photosynthesis, so the rate at which trees release more carbon rises more quickly than the rate at which they soak it up (this also has implications for metabolic ecology: by understanding these effects, via metabolic rate, you can build a bridge between cellular and individual metabolism and the workings of the global carbon cycle). Also, plant growth is limited by other things, so a lack of nitrogen, for example, may limit trees' ability to respond to higher CO2, or warmer temperatures.

The review, which looks at studies in boreal and temperate forests, concludes that we don't really know what's going to happen. Here's what they say…

It is not in doubt that newly established young forests will continue to be C sinks for the foreseeable future. The key question is whether the mature forests that are C sinks today will continue to be sinks as the climate changes. … Forest ecosystem models indicate that the additional terrestrial sink arising from global climate change is likely to be maintained in the short term (over several decades), but may gradually diminish in the medium term. … Because of current limitations on our understanding with respect to acclimation of the physiological processes, the climatic constraints, and feedbacks among these processes – particularly those acting at the biome scale – projections of C-sink strengths beyond a few decades are highly uncertain.

This seems a good argument against tree-planting carbon offset schemes.

How big can a meat-eater get?

Today's news@nature has a story by me (free for a week) about an extremely ITBOAH-esque paper on carnivore energetics and ecology by Chris Carbone and colleagues. This looks at the costs and benefits of different hunting strategies — basically, whether you eat stuff much smaller than you (as tends to be the case with small carnivores, such as hedgehogs), or whether you try and bring down things about your own size (which is what big carnivores such as cheetahs and wolves tend to do).

Eating small stuff is a cheap, low-return strategy, unable to support big carnivores — this limits the maximum size of insectivores. Eating big stuff is high return, but costly, because hunting takes a lot of energy. And it becomes more costly the bigger you get — until at about 1,100 kg, carnivores go out of business.

The largest fossil carnivores are about this size. It also suggests how evolution might paint carnivores into a corner — being big and fierce has obvious advantages, in that you're a top hunter, and you can boss your own species about. But in hard times, you starve. The fossil record seems to show high turnover for fossil carnivores, as the follow this bigger, bigger, bust pattern.

The new paper is the latest in a now quite impressive series of papers by Carbone and his colleagues building links between body size, metabolism, behaviour and population biology. Here, for example, they describe the shift in prey size described above, and here they relate body size, metabolism, prey density and predator population density.

The chances of anything coming from Mars are … 1

In a discovery sure to have major implications, a team of researchers has discovered that the laws of logic and causation are very different on Earth and Mars. The finding suggests that these concepts, often assumed to be universally applicable, may in fact vary from place to place.

"On Earth, we are used to the idea that absence of proof is not proof of absence," explains Mike Trouser, a philosopher at Madeup State University, lead author of the new research. "Similarly, just because a thing might have happened, it doesn't mean that it did happen.

"On Mars, however, we now know that these principles don't apply, and that anything not known to be stonkingly, mind-crushingly impossible must have happened."

As an example, Trouser cites a story in the Guardian on Saturday:

Microbe experiment suggests we could all be Martians

Experiments by an international team of researchers back a controversial theory that life flourished on Earth after primitive organisms arrived aboard a meteorite, itself gouged from Mars by a giant impact.

The story refers to a recent paper in Icarus, which found that various microbes and a lichen can survive being sandwiched in rock and then twanked with a steel plate, to recreate the pressures placed on known martian meteorites.

"You might think that this just shows that contemporary microbes can be twanked with a steel plate and come up smiling," says Trouser. "After all, one cannot tell from reading the abstract whether the experiments exposed the microbes to vacuum conditions, extreme temperatures or high doses of radiation." But in fact, the Guardian quotes the paper (although none of the authors, and no independent sources) as saying:

These results strongly confirm the possibility of a 'direct transfer' scenario of 'lithopanspermia' for the route from Mars to Earth, or from any Mars-like planet to other habitable planets in the same stellar system.

"A strongly confirmed possibility (whatever that is)? Please, you're being too modest," says Trouser.

Initially, Trouser was intrigued why one doesn't see similar results in any other field being reported in this manner. "One doesn't for example, regularly see articles informing us that we don't know for sure that drinking margaritas doesn't make you live longer, or that we can't be sure that cats aren't plotting to overthrow humanity," he points out. "I think the differences in Martian logic now explain this apparent anomaly."

The unique workings of Martian logic don't stop there. At the recent meeting of the American Astronomical Society, it was widely reported that the Viking landers would not have recognized — indeed, would have killed — any life form using hydrogen peroxide as a biological solvent.

The ambiguity of the Viking experiments is nothing new - they have become the grassy knoll of astrobiology. They were designed to look for biological processes — nutrient uptake, gas release — in Martian soil. All gave positive results! Trouble is, so did all nearly all (but not all) the controls. We should probably learn from the Viking experiments to try and design the next life-detectors, rather than endlessly picking over the results.

But, although he believes the existence of H2O2-based life proven, Trouser believes we should also be casting the net wider. "Never mind weird alien biochemistry," he says. "There's plenty of regular life on Mars."

As an example, he cites a 2004 article discussing the general difficulty of recognizing as alive anything that doesn't give you an anal probe and say 'Take me to your leader'. In it, referring to how better we are at spotting microbes now than then, Andrew Steele of the NASA Astrobiology Institute at the Carnegie Institution of Washington says: 'There could have been 10 million bacteria per gram of martian soil, and Viking wouldn't have seen them.'"

"What we now know Steele should have said," says Trouser, "is that there are 10 million bacteria in every gram of Martian soil. For all we know, the Viking mission missed spotting the Flying Spaghetti Monster," he adds. "Hail, then, Martian Flying Spaghetti Monster!"