Wednesday, April 28, 2010

Treading Lightly

Insect eyes, much different from human eyes, are sensitive to polarized light, especially of the horizontal variety -- the kind of light reflected off of bodies of water when the sun hit them. It is known that insects sometimes lay their eggs on glass buildings and other highly reflective surfaces, and these surfaces become ecological traps associated with reproductive failure and mortality. So the researchers decided to test if solar panels, very reflective devices, act in a similar beguiling way. The scientists used imaging polarimetry and measured reflection-polarization characteristics of various types of solar panels when they were presented to mayflies (Ephemeroptera), caddisflies (Trichoptera), stoneflies (Plecoptera), dolichopodid dipterans (Diptera), and tabanids (Tabanidae). They found that at a certain angle (the Brewster angle) solar panels reflect polarized light almost completely. Mayflies, stoneflies, dolichopodids, and tabanids were found to be the most attracted to solar panels. Based on this result, they then tested different panel designs and found that aquatic insects are less attracted to solar panels that have a white borders and white grids, 10-26 fold less attracted. This research highlights the need to research more into solar panel design and placement in the environment.

Here's the paper:
Horváth, G. et al. (2010). Reducing the maladaptive attractiveness of solar panels to polarotactic insects. Conservation Biology (DOI: 10.1111/j.1523-1739.2010.01518.x)

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Ant Farms

Ant-fungus mutualism is one of the many interesting interactions in the animal kingdom. It is a highly evolved symbiosis observed in certain species where the ants cultivate or farm fungus for food -- fungiculture and/or fungivory, if you will. The ants grow, fertilize, clean, and weed patches or gardens of fungi in their underground tunnels and caverns. This mutualism is thought to have originated approximately 45-65 million years ago in the ancestor of fungus-growing ants (Formicidae, tribe Attini). In the course of evolution, a switch was made from the hunter-gatherer lifestyle to a farming strategy. This switch has evolved only twice in ants: (1) in the attine ants and (2) in some species of the solenopsidine genus Megalomyrmex. In this second case the ants either coexist as trophic parasites in the fungal gardens cultivated by attine ants or they take over the gardens from the attine ants. (Read more here) It is estimated that there are more than 200 species of New World ant fungiculturists.

A new study in The American Naturalist reports that these ants update the crops they grow over time. The authors compared the multigene phylogeny to the fossil phylogenies of attine ants as well as the phylogenies of associated fungal clades. Basically, they looked at the accumulations of mutations in short stretches of DNA to see when certain species or strains of ant and fungi emerged. The researchers discovered that the fungi were significantly younger than the ants. For example, leaf cutter ants (one of the best known farmers) diverged from their anty ancestors 12 million years ago, they are significantly younger than the corresponding ant genera. It was thought that the fungus that they cultivate would have to be older, evolutionarily speaking, so that the ants could aquire and domesticate it. However, the fungus these ants farm only arose only 2-3 million years ago. This time difference suggests that the ants are cultivating a new fungal strain, a strain which has been spread to other colonies throughout the ants' range.

The article:
Mikheyev Alexander S., Ulrich G. Mueller and Patrick Abbot (2010) Comparative Dating of Attine Ant and Lepiotaceous Cultivar Phylogenies Reveals Coevolutionary Synchrony and Discord. The American Naturalist: 175, E126–E133. (DOI: 10.1086/652472)


Baby Feathers

It seems that quite a few stories from Nature caught my attention this week. This is another story about dinosaurs, specifically feathered dinosaurs. Not about a new species, their ecology, or their behavior, but rather about the development of feathers.

Two 125-million year old Similicaudipteryx specimens have been recovered from the Lower Cretaceous Yixian Formation of western Liaoning in China. Similicaudipteryx belongs to the group of dinosaurs known as oviraptorosaurs (egg-stealing dinosaurs). The specimens show the dinosaur species in two stages of development - early adulthood and juvenile. The adult has pennaceous or contour wing and tail feathers which resemble a quill pen and are mostly similar in size. The juvenile has longer tail than wing feathers which both have a flat, ribbon-like stem at one end and are pennaceous at the tip. This is the first time that juvenile dinosaurs have been found to have different types of feathers than adults, a transition that we do not observe in modern birds. Other scientists have suggested that the juvenile feathers may be from a moulting phase. The paper's authors explain that if this is the case you would expect the ribbon-like part of the feather to be shorter. They continue on to suggest that the juvenile's partially-pennaceous feathers may be the result of delayed gene expression, expression that is activated early in the life of modern birds.

The Nature article:
Xu Xing, Xiaoting Zheng and Hailu You (2010) Exceptional dinosaur fossils show ontogenetic development of early feathers. Nature: 464, 1338–1341. (DOI: 10.1038/nature08965)
(Full Text -- if you have access, it includes some really great photos and diagrams)


Icy Asteroid

Evidence of water ice and organic materials has, for the first time, been discovered on an asteroid. Josh Emery, from the University of Tennessee Knoxville using NASA's Infrared Telescope Facility on Hawaii's Mauna Kea, found that the spectrum of infrared sunlight reflected by the object was consistent with frozen water. The discovery was confirmed by a team lead by Humberto Campins at the University of Central Florida. Organic materials in the form of complex, long-chained molecules were also discovered. The asteroid 24 Themis is approximately 200 kilometers wide and orbits half-way between Mars and Jupiter in the asteroid belt. As this short distance from the Sun (only about 479 million kilometres) is generally too warm for ice to exist for long, it is theorized that the asteroid may contain an abundance of ice in its interior which is outgassed to replenish the surface supply. This discovery suggests that asteroids may be responsible for bringing some of the water and organic molecules to the barren, developing Earth.

Why the water is there, or how it got there in the first place, is still unclear. Think about an asteroid for a second. Picturing a dry, rocky object in space? You aren't alone. Asteroids are widely viewed as being very dry, especially compared to, let's say, comets. Long-range comets (those coming in from the Kuiper Belt in extremely long and often elliptical orbits around the Sun) contain a lot of water but with a different isotropic signature than water found on Earth, and so they are an unlikely source of Earth's water. In 2006, small comet-like objects with tails were discovered in the asteroid belt and dubbed "main-belt comets," and its this set of objects to which 24 Themis belongs. This asteroid, or main-belt comet, belongs to a set of asteroids that is thought to have formed as a result of a large impact from a larger body, suggesting that the original object contained ice. This has implications for our theories on solar system evolution and planet formation. If this ice-on-asteroid phenomenon is relatively widespread then it is likely that ice was more prevalent in the Main Belt region of the early solar system than previously thought. If you expand this idea to other solar systems and extrasolar planets then water/ice may be more abundant than we thought. And, although that might be a stretch based on a sample size of one, it is an interesting direction to look in. Also, we can't ignore the idea that the asteroid may be from Kuiper belt and was knocked into the inner solar system or arrived there when the gas and ice giants migrated their orbits. Future observations and research will work to determine whether the composition of 24 Themis is typical of the asteroids in this region and if the water on these rocky objects is the same as that found on Earth.

Read more on this discovery at:

(image from -- credit NASA/JPL -Caltech)


In a new paper published online in Nature Geoscience, researchers from UC Irvine and Yale have found that as global temperatures increase, soil microbes become less efficient over time at converting soil carbon into carbon dioxide.

Soil microbes are extremely abundant in most ecosystems around the world. The most numerous of these microbes are bacteria followed by actinomycetes then fungi, soil algae, cyanobacteria, and protozoa. For the purposes of this post I am not including the diverse set of animals that live in soils such as nematodes, microarthropods, earthworms, larger insects, etc. Soil microbes are extremely important in the cycling of the soil nutrients carbon (C), nitrogen (N), phosphorus (P), and sulfur (S). They can regulate the quantities of nitrogen available to plants (think natural fertilizer), and are hugely important in recycling nutrients tied up in organic materials. Many of the soil microbes require organic carbon compounds to oxidize for energy (microbial or soil respiration, usually expired as CO2) and the building materials for their cells. Some microbes get this carbon from CO2, but much of this carbon is collected through the decomposition of organic materials. Soil respiration is known to be affected by such factors as temperature, soil moisture, and nutrient availability.

Naturally, the high abundance of soil microbes and their release of CO2 through respiration has caused many scientists to take a special interest in this system and how it relates to global climate change. It stands to reason that even a few degrees of warming will shift these microfauna into overdrive, increasing the atmospheric CO2. However, this new research shows that, in a warmer environment, soil respiration increases for a short period of time, but if the higher temperatures remain constant, the less efficient use of carbon causes the microbes to decrease in number. This decrease in number decreases soil respiration (decrease in CO2 "exhaled" from soils). The microbes get overheated and "burned out," if you will.

These results contradict some of the results in older models which assume microbes will stay at constant numbers or increase; older models usually do not include enzyme production/activity which is sensitive to temperature and important in the reactions that break down organic carbon. When you get down to the mechanism, its all about how efficiently the microbes can use soil organic carbon. If they are less efficient then populations decrease. If they stay efficient, or adapt to remain as efficient or more so (and remember that microbes can adapt very quickly), then respiration/CO2 emission will stay the same or increase.

Read more here:
Allison Steven D., Matthew D. Wallenstein and Mark A. Bradford (2010) Soil-carbon response to warming dependent on microbial physiology Nature Geoscience: published online (DOI: 10.1038/ngeo846)


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Monday, April 26, 2010


Save the whales, save the planet. No longer mutually exclusive issues. More whales equals more whale poop, and now researchers from the Australian Antarctic Division (AAD) have taken a close look at that whale poop to study its affects on the ocean ecosystem. They have found that baleen whale poo contains large amounts of iron, 10 million times as much as seawater. Ah-ha! A great discovery as it applies to carbon cycling/storage/sequestration (call it what you want) in the oceans. Follow me here...

Iron is a source of food for phytoplankton.
Phytoplankton absorbs atmospheric carbon dioxide.
Phytoplankton is eaten by krill.
Krill is eaten by baleen whales.
Baleen whales excrete iron in their feces.

For a while, it has been suggested that whale poo contained high amounts of iron, but this is the first study to confirm that suggestion. The study also showed that the krill the whales are feeding on (DNA testing of the poo confirms that it contains a lot of krill) also contains large amounts of iron.

Recent geoengineering proposals have called for adding soluble iron to the ocean to seed this phytoplankton growth in order to sequester carbon. One of the reasons it hasn't happened yet is concerns over the consequences this seeding might have on the ocean ecosystem (think massive algae blooms, etc). According to this study, whale poop is an all natural way to reach this goal. True, we could still add iron to the ocean and we would see phytoplankton blooms (and the resultant krill blooms) which would absorb carbon dioxide. But without an increase in baleen whale populations you would not have a natural control mechanism in place.

Stephen Nicol of the AAD believes that before commercial whaling reduced whale populations to the brink, baleen whale feces may have accounted for approximately 12% of the iron in the Southern Ocean. Before commercial whaling, it is estimated that baleen whales consumed about 190 million tonnes of krill per year and produced 7600 tonnes of feces. That's a lot of iron-rich poo. So it stands to reason that if we allow whale populations to recover to pre-consumer whaling numbers then greater amounts of carbon will be sequestered in the oceans, fighting global warming.

The article appeared in Fish and Fisheries:
Nicol, Stephen et al. (2010) Southern Ocean iron fertilization by baleen whales and Antarctic krill. Fish and Fisheries: published online. (DOI: 10.1111/j.1467-2979.2010.00356.x)


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Walk This Way

This is another one of those odd studies that I like to throw in just for a laugh. Granted, its peer-reviewed and published, but wow...just wow.

The objective of this study was to deterimine if people, that is "appropriately trained sexologists," could infer a woman's history of vaginal orgasm just by looking at the way she walks. The researchers had women with known histories of either vaginal orgasm or vaginal anorgasmia (note: not the same as clitoral orgasm) walk normally on a street, and they videotaped this walking for later playback. Then sexologists (ignorant of the women's histories) judged these women as to their orgasmal history.

These appropriately trained sexologists were able to infer orgasmal history simply by watching these women walk (81.25% correct, with 2 false positives). The walk was judged based on its fluid, sensual, energetic, and free movements (apparently qualitative measures). The false positives were thought to be from women who have the capacity for vaginal orgasm but have not yet had experience with them, or have not yet met a man with the knowledge and/or anatomical attributes sufficient to induce one. Additionally, and here's where we get to the quantitative factors (kinda), the sum of the stride length and vertebral rotation was found to correlate with vaginal orgasm history. The authors explain this correlation by saying it "could reflect the free, unblocked energetic flow from the legs through the pelvis to the spine." Um, ok. The authors do point out that there is "a universe of possible unmeasured factors" that could play a role in these results including anatomical features that predispose a woman for vaginal orgasm, certain natural favorable or unfavorable pelvic movements, and confidence about sexual ability.

So, ladies, next time you walk down a street, add a little spring to your step or rotate your vertebra just so to let everyone know you have free, unblocked energetic flow through your pelvis.

Here's the article:
Aurelie Nicholas, Aurelie, Stuart Brody, Pascal de Sutter and François de Carufel (2008) A Woman's History of Vaginal Orgasm is Discernible from Her Walk. J of Sexual Medicine: 5(9), 2119-2124. ((DOI: 10.1111/j.1743-6109.2008.00942.x)
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Friday, April 23, 2010

Dino Eco

The community ecology of the dinosaur age. Scientists argue over community structure in modern settings, so imagine the difficulty in piecing together a dinosaur community.

Scientists from McGill University have used data from the Paleobiology Database to look at the diversity of dinosaur species in North America, specifically from the Maastrichtian formations from 71 to 65 Ma, just before the major dinosaur extinction event. They were interested in alpha diversity (diversity within a particular area or ecosystem) versus beta diversity (diversity between ecosystems or along environmental gradients).

People tend to think that dinosaur fossils are abundant and wide-ranging. This isn't the case; fossils are actually relatively rare and patchy in their distribution. In community ecology, particularly diversity measures, sampling can make a big difference in the results, the more you sample and the more individuals you collect the better picture of the community you get. See where I'm going with this? However, there are ecological techniques to correct for this sampling bias (rarefaction, etc). The scientists in this study corrected for sampling bias by only considering four formations in the northwestern interior that each included more than 100 dinosaur specimens. They looked at the number of unique species at each site (unique meaning found in only 1 place), compensating for the unevenness in samples between sites, and used that to estimate the number of species missing from the fossil record.

They found that the entire Western Interior of North America may have once been populated by a single dinosaur community. These data suggest that differences in species in this region were relatively low, so low as to consider it a single homogeneous fauna that ranged over an entire continent. In terms of the diversity measures, beta diversity was low, there were not multiple dinosaur faunal regions. Low beta diversity is not an unknown pattern. It is something that we can observe in various communities right now, but it is on a much smaller geographic scales. Modern environments can be very patchy allowing different species to exploit various habitat types, and so low beta diversity is seen in smaller, homogeneous habitats. It is likely that the dinosaur communities discussed in this paper experienced large, homogeneous habitats exposed to stable climates. Many were not isolated to small regions and constrained by small, isolated environments. Rather, they were able to colonate and dominate vast areas. This conclusion naturally leads to more questions involving dinosaur migration, gene flow, habitat type, etc.

Its a good start to piecing together the ecology of this era and something which can be updated as more data is collected.

Here's the PNAS article:
Vavrek, Matthew J. and Hans C.E. Larsson (2010) Low beta diversity of Maastrichtian dinosaurs of North America. PNAS: published online. (DOI: 10.1073/pnas.0913645107)

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Warning Sounds

Researchers at Cornell University have published a paper in Conservation Biology that used modelling to investigate population-level responses of timber rattlesnakes to habitat fragmentation. In general, habitat fragmentation reduces the ranges of many species, limits resources, increases competition, alters community structure, decreases species diversity and abundance, increases edge effects, and has many other consequences. Anthropogenic habitat fragmentation can result from a variety of things such as roads, farming, buildings, cities, etc -- basically anything that prevents or severely hinders a species' ability to move across the landscape to favorable areas to live. The results of the model show that habitat fragmentation caused by roads have a significant effect on the genetic structure of these rattlesnakes, they are barriers to gene flow and decreasing genetic diversity. This decrease in diversity has its own set of problems, not the least of which is making the population more susceptible to illness and less adaptable to environmental changes.

Additionally, the researchers looked at these rattlesnakes in 19 different hibernacula (shared wintering quarters) at four regions of New York. Using microsatellite markers they tracked the dispersal patterns of these populations as they left their hibernacula, also tracking their reproductive patterns. They compared these data to the layout of roads and to natural barriers in the areas and found that the roads altered gene flow, effectively isolating these populations. These results were seen in each of the regions and were not affected by road type or age.

The article:
Clark, Rulon W., et al. (2010) Roads, Interrupted Dispersal, and Genetic Diversity in Timber Rattlesnakes. Conservation Biology: published online. (DOI: 10.1111/j.1523-1739.2009.01439.x)

p.s. Don't run over snakes with your car, its bad for the snakes and bad for the environment (not to mention its just plain mean).

Ring Ring

Scientists from the Tree-Ring Laboratory at Columbia University's Lamont Doherty Earth Observatory have compiled tree-ring data from 327 sites in Asia into a new database called the Monsoon Asia Drought Atlas. The tree-rings date back to 1300 AD, which allowed the researchers to put together a year-by-year history of the region's monsoon rains and gives them good weather data for testing climate change models. The sites themselves are necessarily clumped in regions that contain old trees, but these data were used to extrapolate to regions which had no records available. The team mapped annual rainfall across Asia including the Indian and Australian monsoon areas and correlated rainfall patterns with 150 years of sea-surface-temperature recordings to look at how distant ocean conditions affect Asian weather. This is important because monsoons pull moisture from the ocean as hot air rises over the land mass. Looking at historical data will tell us if the drivers of these phenomena are the same now as in the past and to what degree global warming plays in altering these patterns. These data have revealed that past droughts were much longer and more severe than they are in modern times. But, at this point, the analysis has not yielded a lot of climate change model results but has great potential in this respect and will be used as a data source for many modelers.

Read more here:

The journal article:

Edward R. Cook, et al. (2010) Asian Monsoon Failure and Megadrought During the Last Millennium. Science: 328 (5977), 486. (DOI: 10.1126/science.1185188)

and related to it:

Buckleya, Brendan M., et al. (2010) Climate as a contributing factor in the demise of Angkor, Cambodia. PNAS: 107 (15), 6748-6752. (DOI: 10.1073/pnas.0910827107)

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Wednesday, April 21, 2010

What's in a name?

Drosophila melanogaster, a tiny little fly that is a monster in the world of genetics research. There isn't a biologist that hasn't heard of it, and there are thousands of papers about it. The average person is also familiar with this 2.5-millimeter-long fly. You can see it buzzing around trash cans and unripe or overripe fruit on a regular basis.

D. melanogaster has been used for over a century to study genetics. Thomas Hunt Morgan studied the fly in the early 20th century and was the first to discover sex-linkage and genetic recombination, earning him a Nobel Prize. His work, and the work of his students, solidified D. melanogaster as a model organism. This species is easy to obtain from the wild, small in size and easy to handle, is sexually dimorphic, has a short life cycle (10-12 days), is easy to rear in the lab, has fecund females, has a relatively small genome, and is relatively inexpensive to work on. Additionally, the entire genome has been sequenced and many of the genes identified, and there are a variety of mutants available to purchase for study. Exactly because of these reasons, and how much is known about this species, it is also being used in other fields such as behavior, development, neurobiology, biochemistry, and many others. Much of this research is directly related to human conditions and behaviors (are you listening Sarah Palin?).

However, a recent decision at the International Commission on Zoological Nomenclature (ICZN) may reclassify this organism completely. There are about 1,450 species in the Drosophila genus, and the genus Drosophila is part of a larger family of flies called Drosophilidae. As it turns out D. melanogaster (and potentially some other Drosophila species) may actually be more closely related to Samoaia, Captomyza, or Hirtodrosophila. Should this name change happen, will scientists adopt the new terminology? Will we be calling the fly Sophophora instead of Drosophila? Will it be like Brontosaurus to Apatosaurus and Pluto the planet to Pluto the dwarf planet? Perhaps these name changes just take time to take hold.

Kim Van der Linde, one of the very scientists who opened the debate, has argued to keep the name Drosophila attached to the species. A proposal to the ICZN states that the appellation "Drosophila melanogaster" be preserved to prevent confusion in the scientific literature, but that other species in the Drosophila genus be renamed/reclassified as they are less influential.

I can't really say that I completely disagree with her reasoning. I also recognize that, in the age of computers, the titles of already-published papers do not need to be changed, only a new tag added so they can be easily searched. Also, while D. melanogaster is the most widely used of the Drosophila species, to say that the other species are less influential ignores the thousands of studies that research these other species and even compare them to D. melanogaster. In fact, many (if not most) fly labs raise more than one Drosophila species.

Regardless of the name change this little fly will remain a giant in its field.

Here's more on the topic:

Oh, and check these out because they are fantastic!!:

Tuesday, April 20, 2010

Can I get yer number?

I think we can agree: Sometimes this is a big ole confusing world. In this day and age there are just so many choices. While wandering the mall we use window dressings and sale signs to help us decide on stores and products. In the world of the internet we use customer rating systems to help us decide. But what about in other areas where we don't have big red signs and five star rating systems? Areas such as relationships - more specifically, picking a mate.

Social psychologist Alison Lenton and economist Marco Francesconi have conducted a study to try to figure out why and how we choose potential mates. Their experiment of choice -- speed dating. Think about it, it makes sense. A situation where you have to make decisions about whether or not you want to see someone again based only on a few minutes of conversation. The study consited of 84 different speed dating events in the U.K. that included a total of 1,868 women and 1,879 men. These men and women had between 3 and 5 minutes to talk to each other and decide whether or not they wanted to see someone again, a single individual talking to 15 to 35 people in a night.

You would think that people would pick out a date based on what they think they want, but the researchers found that the number of choices is what matters. They found that the more people an individual had to choose from the more likely it was that the men and women would make judgements about a person based on their appearance. So the environment itself is also a factor in decision making. At the larger events the pattern became more pronounced, as more potential matches were presented to a person, the more likely they were to decide based on appearance. The pattern was still there in the smaller events, but the participants were more likely to take the effort to get to know potential dates.

Of course, we are only talking about snap decisions --- the you're-hot-or-you're-not response. I can argue that that serves a purpose, after all you don't want to date someone you are not attracted to initially, but to make real connections people need to have real experiences with each other, become friends.

The take home message? Given a choice, people go for the hotties.

You're shocked, I can tell.

The NPR report including a link to the Morning Edition audio:

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Monday, April 19, 2010

Science is Real

Bottom Feeders

The bottom of the ocean. We're not talking that muck you shuffle your feet through at the beach or the sand you swim by on a SCUBA adventure. We're talking deep, deep ocean. An environment of darkness, extreme pressures, cold temperatures, and limited resources. So when a meal drops in, the critters descend for the feast.

A new article, the April issue of Ecology, describes what happens in the deep sea ecosystem when surplus food drops in. Typically, deep sea animals survive on the dead and decaying matter that sinks from above, which is not as much as you may think. The researchers in this study sent a Remotely Operated Vehicle (ROV) down into the deep waters off of the California coast known as Monterey Canyon (northeast Pacific Ocean). This area receives additional food sources in the form of nutrient-rich sediments that slough off the canyon walls. The ROV took video and soil/mud cores of the canyon floor and walls.

The cores from the canyon floor contained nearly 200 species, but as the cores got closer to the walls there were fewer and less diverse species. Odd, especially since the walls of the canyon have more nutrients than the floor. So what causes this habitat heterogeneity?

Closer to the walls there are larger numbers of bigger, mobile animals such as crabs, urchins, sea cucumbers, starfish, etc. These larger animals consume much of the available food. This has major consequences for the smaller animals that depend on those resources, decreasing their numbers by almost half. So, in some cases, more food is not always better, especially if you are small.

Here's the Ecology article:
Craig R. McClain, James P. Barry (2010) Habitat heterogeneity, disturbance, and productivity work in concert to regulate biodiversity in deep submarine canyons. Ecology: Vol. 91, No. 4, pp. 964-976. (DOI: 10.1890/09-0087.1)

Cobra Attack

The cobra's hood, very cool. But how does it work? A study in the Journal of Experimental Biology takes a look at just that.

Cobras belong to the Elapidae family of snakes. This is a family of venomous snakes which are found in tropical and subtropical regions around the world. Skeletally, the bones in the hood of the cobra evolved from ribs and the associated muscles evolved along with them. Scientists have taken a look at the cobra's defensive display, the "hood flare," and measured the electrical activity coming from the snakes' hood muscles to tease out which muscles are involved in the movement. This experiment found 8 muscles involved in the hood flare. Interestingly, these muscles are also present in non-hooding snakes. The muscles and the nervous system's control over them have evolved to spread the snake's hood. While this research was mostly identifying the muscles themselves, further research will delve into the evolution of these muscles in various snake species.

Here's the story:

Friday, April 16, 2010

Boob Job

Men like big breasts, therefore women evolve larger breasts. Its an evolutionarily solid argument, assuming of course that male preference exerts any pressure on the evolution of female secondary sexual characteristics.

There is experimental evidence (based on questionnaires) that show that men find female breasts visually attractive. (Would it be appropriate to add a "Duh" here?) A relatively new study titled "Eye Tracking of Men's Preferences for Female Breast Size and Areola Pigmentation" examined how men make these visual judgements. The researchers used eye-tracking technology to test if men visually fixated on larger breasts, and for how long, and if areolar color altered male attention.

The results? Well, I think a friend of mine said it best: "Groundbreaking science - men like boobs."

Results of the experiment showed that men rated medium and large breasts as more attractive than small breasts. They also rated dark and medium areolar pigmentation as more attractive than light. Not surprisingly, breast size had no effect on visual fixation. Basically, if there were boobs to look at, men looked at boobs.

Here's the link:

Sexy Algae

Boy meets girl. Boy and girl fall for each other. Boy and girl generate other boys and girls. Its a tale as old as time. Well, kinda. Evolutionarily speaking, there weren't always boys and girls, just its. Those Its reproduced asexually, an efficient if not always a genetically or evolutionarily advantageous reproductive strategy. The evolution of two sexes that swap genes with each other allows for a more diverse and robust gene pool. Usually a great thing. But how did it get that way, at what point did we go from It to Us?

A new study in the journal Science takes a look at Volvox carteri, a multicellular green algae, for the answer to that very question. The authors of the paper compared the sex determining region of V. carteri to that of Chlamydomonas reinhardtii, a unicellular algal relative. They found that this region differed dramatically between these species. The expansion of this region allows for a greater diversity of genes which code for the production male and female gametes. The gametes of C. reinhardtii look identical, but those of V. carteri are distinctly different (egg and sperm).

The mating locus genes of the two species share many genes, but V. carteri's region is almost five times larger, mainly due to additional genes under the control of either male or female programs. Some of these new, additional genes have counterparts in C. reinhardtii that have nothing to do with sex. V. carteri has taken these genes, incorporated them into the mating locus, and started using it in its sexual reproductive cycle. Specifically, the mating locus gene MAT3 has evolved a new role in sexual differentiation, likely a role in controlling cell division and male/female reproductive development.

Future research will involve Gonium, an evolutionarily intermediate species between Volvox and Chlamydomonas. This intermediate will allow researchers to take a look at those in-between steps in the evolutionary process to better understand how this evolutionary change occurred.

Here's the Science article:
Ferris, Patrick et al. (2010) Evolution of an Expanded Sex-Determining Locus in Volvox. Science: 328 (5976), 351. (DOI: 10.1126/science.1186222)


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Thursday, April 15, 2010

Thar She Blows!

A plume of ash from the eruption of Iceland's Eyjafjallajokull volcano has grounded many European travelers. The volcanic ash has shut down airports as it hovered over the Atlantic Ocean and much of north and northwestern Europe. The cloud could hang around for weeks, affecting enormously busy hubs in cities like London.

The volcano spewed forth small, jagged pieces of rocks, minerals and volcanic glass the size of sand and silt. These particles could cause engine failure in aircraft, harm the plane's frame, dangerously heat up and pit its skin, scratch the windshields, and decrease visibility for pilots. Jet engines, in particular, need to "breathe" air to be heated before being expelled out the back to create forward thrust; The gases and particulate matter choke the engines by expunging the oxygen the engine needs to operate and generally gumming up the works.

On a more sciency, and slightly more depressing note, the last time this volcano erupted it lasted for more than a year (Dec 1821 - Jan 1823). As if that weren't bad enough, if the lava from the Eyjafjallajokull volcano melts the glaciers that hold down the top of neighboring Katla then that one could erupt too. The combined spewing of gases and ash would potentially cause an extended change in weather for Europe and the U.S. This is still speculation and what-ifs at this point, but its still a possibility.

Here's the story with a video:

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Science of Pain

I'm posting this video more because its funny than because it is science related. But, as this is a science blog, we can just call it "Behavioral indicators of pain in adults: A study of Brazilian bikini wax patients."

Sorry Big Brother

Brain microchipping - the wave of the future or the road to Stepford? If you live in the state of Georgia there is no need to worry if the voices in your head are real or if you might be a cylon. The Georgia state House committee has approved a measure, and the state Senate has passed a bill, that makes it a misdemeanor to implant microchips, sensors, transmitters, or other tracking devices into people against their will. Sponsors of the bill recognize that widespread chipping isn't occuring, but they are taking a proactive approach to preventing world robot (or cyborg) domination. Georgia lawmakers are not alone in their technology paranoia. Microchip laws have been downed in Tennessee and Virginia and have passed in California, Wisconsin and North Dakota.

Read more here:

Monday, April 12, 2010

Viral Load

In this weeks issue of Nature Nanotechnology, researchers at MIT report to have found a way to mimic plant's ability to use sunlight to split water molecules and make chemical fuel. The team used a virus, M13, an engineered, common, harmless bacterial virus to assemble a nanoscale scaffold needed to split the water molecule, essentially erasing the need for sunlight to drive the process. The virus attracts the water, binds the molecules with a catalyst (iridium oxide) and a biological pigment (zinc porphyrins), and becomes wire-like devices that can efficiently split the oxygen from the water molecules. The virus acts as the scaffolding and the catalyst and pigment trigger the reaction. Kinda like a lightning rod. Over time, these devices lose their effectiveness and so the researchers encapsulated them in a microgel matrix to preserve their uniform arrangement and keep their stability. As this split is considered a "half reaction," the researchers hope to find a similar system to preform the other half of the process, the production of hydrogen. As of now, the hydrogen atoms are split into their subatomic components, and this second reaction would combine them back into usable hydrogen atoms. The resulting hydrogen can be stored in fuel cells and used to generate electricity or make liquid fuels. Currently, the process is expensive, and to compete with other techniques (such as solar power) it would have to become more efficient and the components cheaper. But it is another method in alternative energy.

Here it is:

Volcanic Venus

Venus is the brightest object in the night sky (not including the moon) and the hottest object in our solar system (not including the sun). This planet is super-weird and really intriguing. It is a little bit smaller than Earth, has no moon, has a smaller than expected magnetic field, and rotates very slowly and in the wrong direction. Its year is 244.6 days long and its day is 243 days long. The planet is covered in a thick layer of clouds that are very good at reflecting light (= has a high albedo). The atmosphere is 96.5% carbon dioxide, which traps an extrodinary amount of heat on the planet (a runaway greenhouse effect). It is thought that, at one point in history, Venus may have had oceans, but as the temperature increased they evaporated, UV light broke up the water molecules, and all this increased the greenhouse effect. Radar imaging of the surface, particularly by the Magellan probe in the early 1990's, has given detailed maps of the planet. This imaging has shown a distinct lack of craters, expected when the thick sulfuric atmosphere burns up all but the largest asteroids/meteors. But even these big craters are only about 500 million years old, suggesting that the planet has entirely resurfaced itself (likely caused by a lack of plate tectonics).

In a new online Science paper, evidence is presented that suggests that Venus is still reshaping its surface and cooling its interior via volcanic outpourings. As I said above, it is thought that a dramatic planetary resurfacing event may have occurred 500 million years ago, and this paper suggests that Venus also steadily resurfaces itself through smaller volcanic events. In addition to young craters, the Magellan probe also found nine "hot spots", low rises each a couple of thousand kilometers across, from which lava has more recently flowed. Gravity measurements taken by the probe also revealed plumes of hot rock slowly rising beneath these hot spots that may feed the eruptions. However, the age of the lava flows was unknown.

Planetary scientists from NASA's Jet Propulsion Laboratory (JPL) have taken a look at three of these hot spots using the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on the European Space Agency's Venus Express, still in orbit. Using VIRTIS, the scientists found that the hot spots radiate more heat than the rest of the planet, and were able to infer that the hot spot flows are still pretty fresh an unweathered. Calculations of the flow ages range from a few million years down to 2500 years (young when we are talking planetary history), and the researchers suggest that they are slow, steady outpourings.

Here's the story:
and a NYT article including video:

New Australopithecus

In the Malapa cave north of Johannesburg, South Africa a group of fossils was found that date as early as 2 million years ago. The fossils included a nearly complete skull and partial skeleton of a 11-12 year old boy, an adult female skeleton, and two other skeletons belonging to an infant and an adult female. The fossils belong to a new species called Australopithecus sediba. This new species has a mix of some of the primitive features typical of australopithecines and some of the more modern features typical of later humans. The researchers are necessarily hesitant to call this the missing link, but it is the best candidate yet for an immediate Homo ancestor. It is also possible that the fossils belong to a side branch of late-surviving australopithecines. As the early evolution of humans is still cloudy, particularly the steps in between australopithecines and Homo, it is as yet unclear how these fossils are to be classified.

Here's the report with lots more details and a video:

The articles: (DOI: 10.1126/science.1184944)
and (DOI: 10.1126/science.1184950)

Sushi Love

A recent study in the journal Nature suggests that genes from a marine microbe have been transferred to human gut bacteria. This is the first clear case of gut microbes taking genes from ingested bacteria, allowing them to exploit a new niche. These genes encode for algae-digesting enzymes which break down carbohydrates, carbohydrates that are found in the red algae of the genus Porphyra, known to sushi lovers as nori. What makes this story important? It the clear-cut nature of the transfer, a pretty rare event.

Get more information about the encoded enzymes and their actions here:
The Nature article: (DOI: 10.1038/nature08937)

(image from

Thursday, April 8, 2010

Mr. Roboto

This one is going to blow your mind. Its the robot we've all been waiting for! The innovating, amazing, spectacular...towel-folding robot. Towel folding is, I think we can all agree, not exactly a taxing enterprise on the brain. But, not being a robotics expert, I was not aware that it actually is taxing on artificial intelligence.

A research team out of UC Berkeley has developed software that allows a robot to look at a big, jumbled pile of various towels it had never seen before and then take those towels and fold them into neat stacks. The key to this is the "never seen before" part as robots usually need to have seen an object to recognize an object. Essentially, its all geometry, except that, in the case of cloth, you are dealing with a flexible material that, in the eyes of the robot, form multiple shapes depending on how it is held. The new software uses a grasp point detection algorithm to detect the corners of the cloth to help the robot fold it correctly. This is a method that serve as a platform for helping robots "understand" a variety of materials, rigid and flexible.

Here's the story:

(image from


A team of Russian and American scientists has discovered a new, still nameless, element. The paper, “Synthesis of a new element with atomic number Z=117,” will appear in the journal Physical Review Letters and was reported on in the New York Times yesterday.

Six atoms of this new element were produced by smashing calcium and berkelium together in a particle accelerator. Once the experiment has been replicated and confirmed, the new element will receive its name. At the moment, it is being referred to as ununseptium, a reference to its atomic number, 117. An atomic number refers to the number of protons (subatomic, positively charged particles) in the nucleus of an atom; The number of neutrons can vary. Out of the six atoms created, five contained 176 neutrons, the remaining had 177.

Data from this experiment supports the hypothesis that newly created atoms will become heavier and heavier until they reach a more stable, longer-lived state. This "island of stability" is, and has not been, seen among many artificially created elements which have short, unstable life spans (high decay rates). Stable atomic nuclei occur when the outermost shells of protons and neutrons are filled. Some theories project the center of this "island of stability" to be at 184 neutrons and either 120 or 126 protons. This new element is one more step toward this island and, likely, one more square on the periodic table of the elements.

The NYT article:

Wednesday, April 7, 2010

Cocky Release

A hail storm in Perth on March 22nd killed 57 and injured 24 endangered Carnaby's Black-Cockatoos. Six of the 24 birds had to be put down (one died from injuries), and the other birds have been treated for injuries and released back into the wild of Kings Park. Before releasing the animals, DNA samples were taken and the birds were microchipped for further tracking and study.

The release of the cockatoos coincides with the Great Cocky Count (I love the names Aussies give stuff!) across Perth which maps out the birds' 130 preferred roosts. The Carnaby's Black-Cockatoo is endemic to the south west of Western Australia and it is estimated that only 40,000 birds remain in the wild.

Just a fluffy (or downy, I guess), heartwarming story. Coo.

Here's the link:

(image from

In Plane Sight

A solar airplane. Neat.

The Solar Impulse is a prototype airplane that made its first real flight today. The plane runs entirely on solar energy, deriving said energy from 12,000 solar cellsthat power four 10-horsepower motors. This new machine has a wingspan of 208 feet and weighs only 3,500 pounds. The flying time was 87 minutes at an altitude of just under 4,000 feet. The ultimate goal is to circumnavigate the globe, but this is a good first step, especially considering that it only got 3 feet off the ground for 1/4 of a mile back in December. Future testing will include night flights -- fly to higher altitudes during the day, trading altitude for airspeed, and supplementing with battery power. These night flights will hopefully help the plane make its trip around the world in 2012.

Read the story and see more pictures here:

Pet Protection

In 2008, Switzerland made a news-worthy decision about "plants rights" (that says the arbitrary killing of floral is morally wrong) in a report entitled "The Dignity of Living Beings with Regard to Plants." Not exactly sure how to enforce that one, but good job.

Now, 70% of Swiss voters have rejected a proposal that will provide state-funded lawyers to represent animals in court when trying cases of animal cruelty. This isn't exactly a new idea, certain high up politicans in the U.S. have proposed similar things. Needless to say, nothing has been passed. My opinion? Its a not-in-my-backyard or keep-out-of-my-wallet type of proposal. A majority of people are against animal cruelty (otherwise reality pet police shows wouldn't be so popular), but no one wants to pay for the legal expertise to punish the offenders.

Get the scoop here:

Sweet Ride

This post barely skims the surface of being called science, and only gets close because it involves machines/technology. But, I figure, if I deem circuit board boxers post-worthy then I can post about this too.

The TopCultured site posted a story/photo gallery of "25 Awesome Lawn Mowers." Their awesomeness, or ridiculousness, factor I will leave to you to judge.

Creative Computer Creations

Not sure what to do with that old desktop or laptop computer? Wonder no more. Used/old circuit boards are being recycled into everything these days including jewelry, shoes, and even clothing. Of course, I use some of these terms loosely as these creations don't exactly scream comfort. But, even I'll admit that the jewelry is sparkly (kinda) and has a different, interesting look. And the boxers, dubbed Population Control 2.0, are a conversation starter.

Here's a link:

New Giant Lizard

In 2004, a 2-meters-long, golden-spotted monitor lizard was discovered in the high Sierra Madre forests of Luzon, one of the main islands of the Philippines. It wasn't until last year, when an adult was captured and sampled for DNA, that this lizard was shown to be a new species. This new species has been named the Northern Sierra Madre Forest Monitor Lizard (Varanus bitatawa). It spends much of its time in the trees, its diet consists of fruits and snails (not carrion like many other monitor lizard species), and has specialized claws that help it to climb and gather food. V. bitatawa is related to two other fruit-eating monitor lizards found in the Philippines, most closely to Varanus olivaceus from southern Luzon and nearby islands. It differs from other monitors in scalation, color pattern, body size, reproductive anatomy, and genetic divergence. Additionally, it is ecologically isolated from V. olivaceus (found on the same island) by a 150 meter, low-elevation river valley, restricting V. bitatawa to the forests of the central and northern mountain range. As with many other species in the world, and in the Philippines, these lizards populations are experiencing massive population declines due to habitat destruction and hunting and trapping for the pet trade.

The article in Biology Letters: (DOI: 10.1098/rsbl.2010.0119)

The NPR article:

Monday, April 5, 2010

Rappin' Science


Long Range Tree Sperm

My car is yellow. I don't own a yellow car.

As of this weekend the pollen is out in force. Published online in the American Journal of Botany is a new study about the long distance dispersal and germination abilities of pine pollen.

The loblolly pine (Pinus taeda) is a commercially important forest species that grows over 60 million acres of the the southern United States. It is a rapidly growing tree that reaches a height of approximately 35 meters and has needles in bundles of three that measure 12-22 centimeters long. The male cones start shedding their pollen between February and April, the peak being reached in late March and early April.

The author of the article, Claire Williams, traveled between the North Carolina barrier islands and the mainland between 2006-2009. Her objective? Collect loblolly pine pollen that had been blown far offshore to see if it could still germinate. Williams and her colleagues used hand-held spore samplers, and they sampled from helicopters and ferries.

A majority of the pollen shed by the pine trees lands locally, but some catches the wind and can go surprising distances, up to 1800 miles. During that travel the pollen is exposed to the elements - extreme temperature, UV radiation, and moisture. The sampling found pollen 2000 feet up into the air and as far as 25 miles offshore. Of that pollen, 50% was still viable, distance was not a factor.

Viable long-distance pollen dispersal is a useful adaptive tool but can cause problems for agencies (like the USDA) that approve the use of transgenic trees. At present, transgenic trees are not planted but because of the commercially profitable nature of these trees it is a possibility they may be in the future. Studies like this show that tree DNA can become more widely spread than previously thought, potentially spreading transgenic traits such as drought tolerance and disease and pest resistance. A problem that increases with the age of the tree - a long lived species that produces more pollen the older it gets. The good news is that this long-distance pollen could potentially reach areas affected by climate change, increasing the gene pools and possibly the adaptability of some populations.

Here's the paper:
and a write-up:

Power Animals

Recently, my friends and I had a discussion about what would be our power animals. We didn't think of these.

Planet Spotting

Despite my claims in the previous Pac Man Moon story, I do occasionally go outside at night and look up at the stars (especially at big events like eclipses, comets, meteors, etc). If you do also, then you might find this story of interest.

Apparently, Mercury was at its closest and Venus at its brightest this weekend, but as I was coughy-sick I didn't walk the 10 steps out of my door to take a look. However, we have another chance to see these planets in action. They will be roaming around the sky through April 12th in the paths illustrated here:
If you like looking at planets then take a gander at Saturn and Mars on either side of the Leo constellation (how to find it: around 9pm when the constellation is at its highest. You shouldn't need binoculars or a telescope to see them.

Read more here:

So Quarky

In thinking about how to start this story I figured that an itty bitty lesson in particle physics was in order. Now, a word of warning: I'm not, and have never been, a particle physicist. At least not in this dimension. So I'm going to try and keep it simple for your sake, my sake, and the sake of the word count. Here's hoping it comes out intelligible:

In modern theory we have the Standard Model, a name given to the theory of fundamental particles and their reactions (we're talking all the stuff that makes up protons, neutrons electrons, etc.). This theory has been extremely useful the field of particle physics as well as other areas of study that use its principles. You've no doubt heard all the news hype about the Higgs boson, particularly in relation to the Large Hadron Collider (LHC). The Higgs boson is an additional, as yet theorized but undiscovered, particle that lends mass to these other, fundamental particles.

What other particles? I'm glad you asked. They are the fundamental building blocks from which all else is made. In the Standard Model there are 12 fundamental matter particle types (and, of course, their corresponding antiparticles). These 12 types are divided into 2 classes, of 6 particles each, called quarks and leptons (the 6 being 12 if you count antiparticles). Since this story talks about quarks in particular I just define those. Quarks are the constituents of hadrons such as protons and neutrons. Remember I said there were 6 types? They are up (u), down (d), charm (c), strange (s), top (t), and bottom (b). They experience all four of the fundamental forces (electromagnetism, gravitation, strong interaction, and weak interaction), although gravity is negligible at these scales, and are grouped into 3 generations. The first (and only to be found in nature) being up and down quarks, the second charm and strange quarks, and the third top and bottom quarks.

Hopefully, that made something resembling sense. My brain hurts and we are just getting to the story.

A team of physicists, using more computing power and simulations than we can probably conceive of, have calculated the masses of up quarks and down quarks. This new calculation is 20 times more precise than previous ones. It could be a big help to scientists working at facilities such as the LHC, not to mention other theorists who could incorporate it into the Standard Model (which treats quark masses as arbitrary). It is known that quarks are bound together by the strong interacting force (strong force), but this hold is so tight that you can't isolate one quark from another. So you can't measure the mass of a single quark. Particles that are made up of quarks are, as you would expect, even more complex. A proton has two up quarks and one down quark while a neutron has two down quarks and one up quark -- all held together by gluons (quark interactions or vector bosons). Oh yeah, and don't forget to add the quark-antiquark pairs that come into and out of existence. When you start adding things up, the valence quarks (those original 3) make up under 2% of a proton's mass. This is where the theorists step in.

Physicists have used an approach called lattice quantum chromodynamics (lattice QCD) that simulates these particles within a hadron by modeling it as a grid of points (a lattice). When you place the quarks and gluons on the grid and simulate their interactions you can calculate the masses of hadrons. In the past, this procedure lended a sizable uncertainty to the masses of the quarks. Here, the scientists were able to calculate the ratios of the charm-quark mass to the strange-quark mass and then combine this with another group of ratios of strange-quark mass to up-quark mass and down-quark mass. The resulting ratios were of a much smaller uncertainty (from 30% to 1.5%) than in the past. "The team finds that an up quark weighs 2.01 +/- 0.14 megaelectron-volts, whereas a down quark weighs 4.79 +/- 0.16 MeV. That’s 0.214% and 0.510% of the mass of the proton, respectively." More testing needs to be done to see if these results hold up, but this is undoubtedly an extraordinary achievement.

Whew...I need a drink...

Get more of the story here:

(image from


Picture a lagoon nestled in the Cerro Galán volcanic caldera, high in the Andes mountains. The lagoon is located 4,600m above sea level (meaning low oxygen), is hyper alkaline at a pH of 11, has a salt concentration five times higher than sea water, has an arsenic concentration 20,000 times higher than US drinking water, has a ultraviolet (UV) light exposure level 40% higher than that in the lowlands, and is exposed to gaseous sulfur leaking from volcanic vents. That pretty much sums up what an extreme environment includes. What would you expect to find there? Likely only a collection of stromatolites, if anything at all.

Well, an Argentinian research team expecting to find just that in fact found flamingos surviving on a diet of microorganisms (as yet unidentified) living in the lagoon. The scientists are working to identify the bacteria in hopes that these extremophiles may yield medical or commercial properties - such as UV resistance, enzymes that function in extreme conditions, antioxidants, etc. Getting away from the greedy money side of it, the discovery may also yield clues on the development of life on Earth - an environment with low oxygen, high UV, and high pH, all conditions found in the lagoon.

Check it out here:

(image from

Thursday, April 1, 2010

Mmmm...Brains!: Using Mathematics To Save Us On Z-Day

Updated and Expanded: 1-14-2014

In the science of the undead it's publish or perish, and rise to publish again. Make no mistake, the threat of zombies is real and Z-day is closer than you think. If caught unprepared you may wake up with a flesh-hungry, reanimated corpse on your doorstep.

But, realistically, can we use what we already know to examine a zombie outbreak?

Philip Munz, Ioan Hudea, Jo Imad, and Robert Smith? (yes, there really is a question mark in his name) wrote a book chapter in 2009 called "When Zombies Attack!: Mathematical Modeling of an Outbreak of Zombie Infection."  This article models a zombie attack, using basic biological assumptions and equations currently used to examine the spread of infections such as HIV, malaria, and HPV. It also takes into account what we know (or think we know) about zombies: they are cannibalistic, they move in small, irregular steps (using the popular slow-zombie rather than the newer fast-zombie), they show signs of physical decomposition, and their bite changes a non-zombie into a zombie.

Munz et al.'s basic model considered three basic classes: susceptible, zombie, and removed. Susceptibles become deceased through natural, non-zombie-related causes but can become zombies through bite/blood transmission. As it suggests, the removed are those who have died via attack or natural causes. So, assuming a short time period where the birth rate is constant, zombies can only come from the resurrected or susceptibles, and zombies move to the removed class when they are defeated. Using these variables he was able to put together a simple model. Then things got more complicated, as models tend to do.

The authors took his basic model and ran it through different scenarios, adding parameters as needed. The first factors he looked at were mass-action incidence and random contact. These basic additions show a disease-free equilibrium to be unstable and a human-zombie coexistence to be impossible. Next, they revised the model to include a latent class of infected individuals which shows that although the zombies will still take over, it will take approximately twice as long. The next version of the model was run with a partial quarantine of zombies then there will be a slight delay in the time to eradication but, ultimately, the zombies still get us. Then the model was run assuming a cure has been found that allows a zombie to return to human form but does not offer immunity. In this case, humans are not eradicated, but only exist in low numbers. Better but still not great. Finally, they attempted to control the zombie population by strategically destroying them as Max Brooks suggests in his book World War Z - An Oral History of the Zombie War. This scenario assumes that it would be difficult to have the resources and coordination needed and so more than one attack would be needed resulting in an impulsive effect. This model found that after 2.5 days, 25 percent of the zombies destroyed; after 5 days, 50 percent; after 7.5 days, 75 percent; and after 10 days, 100 percent of zombies were destroyed. It is important to note that the time scale of this model is short. If the time scale of the outbreak increases then you get a doomsday scenario with a complete collapse of civilization, every human infected or dead. Essentially, if we can contain the outbreak initially and quickly then we can save our own asses (literally).

Next, consider Daniel Lakeland's Improved Zombie Dynamics model over at his Models of Reality blog. He builds on the above model, taking into account several factors that Smith?'s group did not include. Lakeland's model removes the short timescale, allowing the human population to grow at approximately 4.5 percent per year growth through a birth rate of 6.5 percent and a death rate of 2 percent. He also tackles the classification categories. Once a zombie is categorized as removed it can not be reanimated and therefore a special class of fully removed zombies should be required. Also in this fully removed category should go those human who died of natural causes too long ago to be zombified (basically, skeletons). Resurrection from the dead is assumed to be a relatively rare event, 1 percent per year, and rotting of the dead to be much faster, perhaps 5 percent per dayAny good model should also take human experience into account. Surviving humans have learned how to fight zombies and avoid zombification.  Initially, the probability of a human winning a zombie fight is relatively low, about 0.1 percent, but then again the percentage of zombies starts out low too, about 1 in 10,000. But the zombie-killing learning parameter is quite large. Elite zombie killers, in particular, serve an important role in that they are most efficient, rapid, and effective in zombie eradication. However, this skill decays at approximately 1 percent per day in the absence of education. The lack of skill and readiness makes all the difference and causes the probability of a human victory to decline rapidly to zero. It is this, the education parameter, that Lakeland's model found to be most important. Reasonably large numbers of people should be at the very least vigilant with an elite force (perhaps 4/10,000 people) there to drop some zombies. So watch some zombie movies, ya'll.

ResearchBlogging.orgPhilip Munz, Ioan Hudea, Joe Imad, & Robert J. Smith? (2009). When zombies attack!: Mathematical modelling of an outbreak of zombie infection Infectious Disease Modelling Research Progress, 133-150

Lakeland, D. (2010). Improved zombie dynamics. Models of Reality blog, 1 March.

Robert Smith?'s articles:
"A report on the zombie outbreak of 2009: how mathematics can save us (no, really)"
"What can Zombies Teach us about Mathematics?"

NPR interview with Robert Smith?: "Who Will Win In Human, Zombie War?"
CBC News Story: "Zombie Math"

Some other things to consider:

This unpublished paper by Andrew Gelman on a way to study zombies indirectly using surveys that don't risk the interviewers: "'How many zombies do you know?' Using indirect survey methods to measure alien attacks and outbreaks of the undead"

Blake Messer over at The Tortoise's Lens blog creates a model where looks at the Munz model and he takes into account that the humans who survive do so for a reason (they are stronger, faster, smarter, etc.) and the distribution of these people in a two dimensional landscape. Read his post called "Agent-Based Computational Model of Humanity's Prospects for Post Zombie Outbreak Survival"

(image from
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