Culturing Science – biology as relevant to us earthly beings

Swarms of tasty cicadas don’t help the birds — what gives?

Every thirteen years they come. After over a decade underground, they build burrows to the earth’s surface and emerge in synchrony, clawing and crawling up through the soil, rip their skins down the back and are reborn as adults. And after a month, they will be dead, whether consumed by the animals awaiting their arrival or as a part of their lifecycle, with the females having laid eggs in the soil to develop for another thirteen years.

A cicada emerging on April 26, 2011 in Harmony, NC. Flickr user Janet Tarbox in the 2011 Brood XIX album

Some cicadas emerge every single year — annual or “dog days” cicadas — but two broods are on much lengthier cycles. This year, 2011, Brood XIX cicadas have already begun emerging throughout the southern United States. In 2004, I was lucky enough to experience the emergence of Brood X and won’t have the honor again for yet another decade, after a total of 17 years in 2021.

Their peak in 2004 coincided with Princeton University’s alumni weekend — which I attended as a bored high schooler —  and what poor timing for that event! The endless drone of the insects forced us to yell just to make conversation; the air was so dense with their swarms that they would fly into unsuspecting Princeton grads with a size and velocity that was actually painful; sidewalks and windshields were splotched with the pale green stains of the squished deceased.

Besides providing a weekend of entertainment for high school hooligans witnessing the torture of exasperated ivy-league graduates, the emergence of millions upon millions of cicadas for just a single month provides an ephemeral pulse of resources. Once dead, their decaying bodies add nutrients to the soil (1) and streams (2), increasing soil microbes (3) and detritivorous insects (4), while their predation on roots as nymphs and plants, young ones in particular, as adults can decrease tree (5, 6) and plant (7) growth in the cicadas’ emergence year.

This deluge of huge, nutritious bugs should be a boon for their predators as an undepletable food source. While one study (8) found no change in a population of white-footed mice after Brood X emerged, the same study saw the number of short-tailed shrews increase four-fold — now that’s a lot of shrews!

An Eastern Kingbird going after a cicada. From Flickr user Michaela Sagatova

So you’d probably expect a similar reaction from insect-eating birds — that some would have no change, but some would benefit greatly from the cicada surge, especially since their migratory nature would allow them to gather by the cicadas during emergence years. But when ornithologist Walter Koenig and entomologist Andrew Liebhold compared populations of 24 bird populations over the course of 37 years from the Breeding Bird Survey data set with periodic cicada pulses (9), they found only two species that showed up just for the cicadas — both North American cuckoo species. Out of the other 22 species, only 6 populations increased; the remaining 16 declined, and 5 of them with statistical significance.

What gives?

They had three hypotheses to explain why so many bird populations were decreasing, according to a large observation-based bird survey, even when the birds were practically drowning in ample food resources. The overwhelmingly loud noise of cicada calling could drown out bird calls for the birdwatchers, creating an observer bias artificially lowering the reported number of birds in the area — the detectability hypothesis. Alternatively, all the racket could keep the birds from hearing one another, disrupting their communication and driving them to quieter areas with fewer cicadas — the repel hypothesis. Or the birds populations could be declining for another reason, affecting them beyond the ranges of the cicadas — the true decline hypothesis.

Brood XIX cicada on May 3, 2011. Flickr user Patrick Coin

Koenig and Liebhold just published a reanalysis (10) in March 2011 in Ecology to test their ideas about why these bird populations are dropping. Again, they used the Breeding Bird Survey data for the 12 species showing the greatest decline from their previous paper, but also compared populations to the counts from the previous winter (Christmas Bird Counts) and incorporated notes about cicada prevalence from the counts where they could.

Their results supported the true decline hypothesis — that the birds’ population declines are not related to the emergences at all. They suggest that the drop in population numbers could be an indirect effect of the cicada emergences, however. The voracious plant consumption of the cicadas could be negatively affecting other insect prey sources or otherwise adversely impacting the immediate habitat. Additionally, while North American cuckoos are not typically nest parasites, this behavior — laying their eggs in the nests of other birds — has been observed when cuckoos are under intense competition with one another, as in this situation.

Is that cat hungry or just looking to cuddle? By Flickr user Allan Janus, 2004

Some scientists (11) suggest that cicadas emerge on such odd timescales — 13 and 17 years, I mean, c’mon! — specifically to mess with their predators. If they emerged too frequently, their tactic of completely overwhelming the area with their presence, basically guaranteeing that many of them will successfully reproduce no matter how many housecats and cuckoos are fed — predator satiation — wouldn’t work. If they emerged more frequently, the gains of their predators from the cicadas’ previous emergence may still be lingering, effectively increasing their predators’ numbers each year until the cicadas themselves were overrun. (A hard scenario to imagine, I know — that would take even more shrews!)

But could the cicadas have evolved to take advantage of such a long-term concept? That they would have to effectively “wait” for their predators to be on the decline before they emerge again? Some biologists have even hypothesized that the latency periods of 13 and 17 years are significant because they are prime numbers! Take it away, Dr. Nicolas Lehmann-Ziebart:

[A]ssume that cicada predators consist of species having cyclic or ‘‘quasi-cyclic’’ dynamics with either two- or three-year periods. This leads to high predator abundances, and high predation rates, in years divisible by either two or three. Because primes are the only numbers between 10 and 18 that are not divisible by 2 or 3, broods of prime-period cicadas frequently escape high predation levels and hence tend to dominate hypothetical cicadas with nonprime periods. This mechanism for generating prime numbers relies on either externally driven two- and three-year cycles of predators, or predators that have strict fecundity schedules creating dynamics that tend to show two- or three-year oscillations.

Lehmann-Ziebart and his undergrads suspect that the cicadas emerge in these odd patterns as a balance between predator satiation and competition within the cicadas themselves. They, unfortunately, couldn’t find an obvious explanation for the prime numbers, though suggest it could have to do with a genetic counting mechanism.

Another explanation for this odd pattern of bird decreases coinciding with great cicada food sources is shoddy data. The Bird Breeding Survey is performed by mere citizens after all — can’t trust them! JUST KIDDING! There have been criticisms of the survey, including new observer bias (a n00b bird counter gets better each year, so the early years are unreliable and this bias is not accounted for), its road-based sites and transects for the counter’s ease could cause bias due to car traffic, and variation in the number of counters year-to-year. Nonetheless, the survey covers an incredible amount of ground — with each route covering nearly 25 miles — and over 400 bird species and has been ongoing since 1966. Pretty good for any large-scale data set which will always have caveats.

It looks like the jury’s still out on why bird populations decline during cicada emergences, though I suspect it’s a combination of many factors — bird communication problems, detectability bias, ecosystem changes induced by the cicadas and the overall variability in bird populations and routes.

This post was chosen as an Editor's Selection for Wheeler, G., Williams, K., & Smith, K. (1992). Role of periodical cicadas (Homoptera: Cicadidae: Magicicada) in forest nutrient cycles Forest Ecology and Management, 51 (4), 339-346 DOI: 10.1016/0378-1127(92)90333-5

(2) Pray, C., Nowlin, W., & Vanni, M. (2009). Deposition and decomposition of periodical cicadas (Homoptera: Cicadidae: Magicicada) in woodland aquatic ecosystems Journal of the North American Benthological Society, 28 (1), 181-195 DOI: 10.1899/08-038.1

(3) Yang, L. (2004). Periodical Cicadas as Resource Pulses in North American Forests Science, 306 (5701), 1565-1567 DOI: 10.1126/science.1103114

(4) Yang, L. (2005). Interactions between a detrital resource pulse and a detritivore community Oecologia, 147 (3), 522-532 DOI: 10.1007/s00442-005-0276-0

(5) Speer, J., Clay, K., Bishop, G., & Creech, M. (2010). The Effect of Periodical Cicadas on Growth of Five Tree Species in Midwestern Deciduous Forests The American Midland Naturalist, 164 (2), 173-186 DOI: 10.1674/0003-0031-164.2.173

(6) Koenig, W., & Liebhold, A. (2003). Regional impacts of periodical cicadas on oak radial increment Canadian Journal of Forest Research, 33 (6), 1084-1089 DOI: 10.1139/X03-037

(7) Yang, L. (2008). PULSES OF DEAD PERIODICAL CICADAS INCREASE HERBIVORY OF AMERICAN BELLFLOWERS Ecology, 89 (6), 1497-1502 DOI: 10.1890/07-1853.1

(8) Krohne, D., Couillard, T., & Riddle, J. (1991). Population Responses of Peromyscus leucopus and Blarina brevicauda to Emergence of Periodical Cicadas American Midland Naturalist, 126 (2) DOI: 10.2307/2426107

(9) Koenig, W., & Liebhold, A. (2005). EFFECTS OF PERIODICAL CICADA EMERGENCES ON ABUNDANCE AND SYNCHRONY OF AVIAN POPULATIONS Ecology, 86 (7), 1873-1882 DOI: 10.1890/04-1175

(10) Koenig, W., Ries, L., Olsen, V., & Liebhold, A. (2011). Avian predators are less abundant during periodical cicada emergences, but why? Ecology, 92 (3), 784-790 DOI: 10.1890/10-1583.1

(11) Lehmann-Ziebarth, N., Heideman, P., Shapiro, R., Stoddart, S., Hsiao, C., Stephenson, G., Milewski, P., & Ives, A. (2005). EVOLUTION OF PERIODICITY IN PERIODICAL CICADAS Ecology, 86 (12), 3200-3211 DOI: 10.1890/04-1615

Written by Hanner

May 4, 2011 at 11:15 pm

Lazy Sunday Video: What NASA does

“Now that I think about it, many universal constants are more certain than death and taxes..”

Funny video, starring a cute boy, about how NASA helps to increase the awesome of the USA! Why is NASA worth .45 cents of each of your tax dollars?

I’m convinced.

NASA: Decreasing the suck. Increasing the awesome.

Written by Hanner

May 1, 2011 at 10:35 am

What is radiation anyway? My attempt to demystify nuclear energy

I’m not a physicist and, as such, would appreciate comments/emails alerting me to any errors! And yes, I did feel like I had to write this whole thing up before approaching radiation ecology. Welcome to my brain.

White Sands, New Mexico, 1954. An FBI agent, a police sergeant, and two scientists venture into a sandstorm, goggles pressed to their eyes, with one goal in mind: to find an odd footprint that they suspect is connected to recent area deaths. The scientists exchange knowing glances when they find it. “Something incredible has happened in this desert,” Dr. Graham says.

A minute later, the air swells with alien screams and the blinding sand clears to reveal their source: a giant ant, nearly 8 feet long. The agent and sergeant shoot frantically — “get the antennae! get the other antenna!” Graham yells. With its senses disabled, the ant collapses into machine gun fire. The team looks on in wonder: what is this thing and where did it come from? “It appears to be from the family Formicidae: an ant,” says Graham. “A fantastic mutation probably caused by lingering radiation from the first atomic bomb.”

Poster from Warner Brothers' 1954 horror film, "Them!" Image: Wikimedia Commons

This is a scene from the 1954 film Them!, one of many horror movies inspired by the first atomic bomb tests in the southwest United States. (And a great one, at that!) This idea seems preposterous now: radiation causing mutations that cause ants to grow to enormous sizes and feast on humans. Or atomic waste dumped into the ocean landing upon a human skull, creating a murderous zombie. Or a woman’s irradiated brain causing her grow to 50-feet — “incredibly huge, with incredible desires for love and vengeance!”

But is it really so preposterous? Radiation has taken on its own character, not only because of the immediate fears represented in film and books to the present day, but also because it is so hard to describe. It’s simultaneously envisioned as vats of poisonous waste, particles streaming from the sky — fallout — that can burn human skin, and atoms suspended in the air or water that can be incorporated into living tissue, festering there for decades and causing miniscule damage to DNA.

When I spoke to Tim Jannik of the Savannah River National Laboratory for The Scientist, he had to remind me what radiation really is. “What people often forget is that radiation is simply just energy,” he said. “When you get exposed to radiation, your body is absorbing energy.”

Ward Whicker, a radioecologist at Colorado State University whom I also interviewed for The Scientist, pushed it further: not only is radiation a simpler idea than that held in the public mindset, but it is also omnipresent in our lives. “People in general have a hard time understanding that we live in a very radioactive environment naturally,” he said. “Life has evolved in a radiation environment.”

Of course, we mostly think about radiation during times of crisis, whether it’s concern about nuclear weapons or, more recently, the flooding and subsequent breakdown of the Fukushima nuclear power plant. After discussing radiation for several days in terms of its hazard and then having these conversations of its basic nature in our environment, I realized that I really couldn’t remember very much about what radiation actually is! One thing led to another — or, rather, one wikipedia page led to another — and, after a few days of research, I felt I actually understood, on a basic level, how radiation works.

It felt wonderful to have radiation demystified! So, in case some of you are also struggling to think back to high school physics, I thought I’d write up what I learned.

The split nucleus

The cover of Weird Science #5, (c) EC Comics 1951

Radiation is a broad term that has taken on a very specific meaning for those of us who aren’t physicists. Radiation, from the same root as “ray,” describes something that travels in waves — and if you can think back to high school physics, remember that if something is a wave, it is also a particle. So sunlight — a form of radiation — is a wave, but is also composed of particles, photons. The same goes for UV and radio waves: Also particles. What we call “energy,” some amorphous force, is actually matter. Henceforth, when I mention “radiation” I will be referring to nuclear radiation: the waves/energy/particles that radiate from a nucleus.

As long as we’re on the subject of words that have taken on their own mythology, I may as well add another to the mix: nuclear. For some reason, I have two compartments for the word “nuclear” in my brain. One describes those tightly packed balls in the center of atoms, the nucleus, around which race electrons in various configurations. The other is more conceptual: a word that describes a great power, much like the One Ring, that can be used for good hypothetically, but is also dangerous.

But, of course, the actual meanings of nuclear in each case is one and the same, as nuclear power and all its gifts and danger are the product of activity at the nucleus of atoms — in particular, its breaking apart.

It takes a great deal of energy to compact neutrons and protons together into a tight ball and hold them there. So you can probably imagine that, if the nucleus does manage to break, energy is released. And this energy release, my friends, is nuclear radiation. (Its actual movement is also called radiation, but I’m referring to radiation as the actual energy.) There are different kinds of nuclear radiation — alpha particles, beta particles, gamma particles, neutrons, and others — that differ in what materials they are able to penetrate and the strength of the energy they carry. There are two ways a nucleus can break:

  1. It is unstable enough to disintegrate on its own.
  2. If it collides with another particle or nucleus with enough force.

A nucleus that is unstable enough to break apart on its own is an isotope, meaning it’s picked up a neutron or two that fly through the air constantly. This heavier nucleus cannot be held together by the same amount of energy, and thus it typically splits into smaller elements, a neutron or few, and energy. There are around 340 naturally-occurring isotopes that we know of that are radioactive in this way, but that’s leaving out some that (a) split so quickly that we can’t recognize their existence in the first place or (b) haven’t split yet since the formation of the earth, but they may still.

The second way for a nucleus to split is to be struck with another particle, a neutron for example, with enough force that the energy holding the nucleus together is disrupted and it breaks into smaller parts. This is the reaction that scientists organize in particle colliders to try and identify all the little particles released at the breaking point.

There really isn’t a huge distinction between these two methods: In both cases, a neutron strikes a nucleus, disrupting the energy holding it together, and causing it to break. It’s just a matter of time — either it happens immediately, or the neutron joins the nucleus for a little and, eventually, causes its demise.

This is the reaction that occurs in nuclear power plants. Many of these plants use Uranium-235, the only naturally occurring isotope that can sustain a nuclear chain reaction. A nuclear chain reaction is when one nuclear reaction leads to one or more — like knocking the first domino in a row. When Uranium-235 is struck with a neutron, it can release 3 more neutrons during its breakdown. If just one of these three manages to strike another atom of Uranium-235, another reaction occurs, ad infinitum.

And the main point: When any of these reactions or related ones occur, a bit of radiation (energy/waves/particles) is released with it, the extra energy that once was part of the nucleus and held it together. This energy is collected in nuclear power plants to generate electricity by heating water, for example. And it’s this energy that can do damage to our cells.

The Human Torch is born. Fantastic Four #1 (c) Marvel Comics 1961

The danger of radiation

Most forms of radiation in our day-to-day lives are relatively benign — visible light, microwaves and radio waves, for example — and can’t do much harm, with their energy simply causing heat, if that.

But some radiation, such as alpha particles or UV rays, are tough little buggers that can interact and change other molecules that they run into by pulling off electrons. And it’s these resulting molecules — the oft advertised free radicals — that can damage DNA, causing mutations. With enough DNA damage, the cells commit suicide (apoptosis), and large amounts of cells dying quickly is what makes people exposed to large amounts of radiation to become sick.

If you’re in the vicinity of a large amount of radiation — such as when nuclear power plant cooling is disrupted, nuclear fuel is ignited, as at Chernobyl, or a nuclear bomb explodes — a lot of energy is reaching your body, both in the form of heat, which can cause burns, and nuclear radiation.

(At this point, this radiation chart may be of use – it’s the best one I’ve found yet (thanks to Jeanne Garbarino).)

Cells in your body that divide very rapidly are the first to cause illness, as losing a group of these can quickly effect the total number due to their exponential growth. These are blood-forming bone marrow cells, and their damage can cause anemia due to a drop in red blood cells and a weakened immune system from a drop in white blood cells. Intestinal cells divide quickly, but not as rapidly as bone marrow cells, so they’re the next to be affected, causing symptoms such as nausea and vomiting, dehydration, and digestion trouble. At very high radiation doses, the cells that don’t divide are affected, in particular nerve cells, causing neurological problems from headache to coma. And these problems combined can kill.

If the radiation manages to damage DNA without killing the cells, this damage could still cause problems that could potentially lead to cancer later in life. Another concern for cancer-causing radiation is when radioactive isotopes accumulate in tissue, decaying and releasing energy within the body. (Read on! I dare you.)

Bioaccumulation of radioactive isotopes

Fantastic Four #1. (c) Marvel Comics 1961

Much of the concern in the aftermath of the Fukushima reactor accident has been about various radioactive isotopes: Iodine-131, Cesium-137, and Strontium-90, to name a few. These are isotopes that are taken up by the body when eaten and are incorporated into tissues because their biochemistry is similar to iodine, potassium, and calcium, respectively.

Non-radioactive iodine is necessary for proper thyroid function, but when Iodine-131 is taken up by the thyroid instead, the isotope is stored in the thyroid, slowly able to release its radioactive energy and particles over time. This long-term exposure in a very small area can lead to thyroid cancer. However, Iodine-131 decays relatively quickly: In just 8 days, a sample of Iodine-131 will be half the size it began. In other words: on average, half of the nuclei in the sample will have decayed after 8 days, proportional to but not an exact measure of the decay rate of a single nucleus (Thanks, Liz!). However, it releases alpha radiation, a stronger form of radiation that creates free radicals more easily and quickly, so it’s best to avoid it despite its short lifespan.

Cesium-137 and Strontium-90, however, take around 30 years each to halve in size, slowly releasing radiation over that period of time. Cesium-137 imitates potassium and is taken up into muscle tissue where it can remain for half a year before it is recycled out by proper potassium, giving it a fair bit of time to release radiation. Strontium-90 takes the place of calcium, building up in bone and bone marrow. Unfortunately, this isotope gets stuck there and isn’t cycled out like Cesium-137, and can cause bone cancers and leukemia.

These latter two — with 30 year half-lives — can accumulate in plants or animals and, when humans ingest them, become incorporated into our bodies. That is the fear behind much of the environmental impact talk: Will Strontium-90 enter the food chain? How far from the reactor will it spread? And how long do we have to wait before the food is safe again?

The answers to these questions are mostly unknown because we simply don’t have enough experience with them. As I will elaborate on in my next post, very little work has been done studying the ecosystems at Chernobyl, giving us little insight into how these isotopes remain in the environment.

Congratulations! You made it through. I hope I was able to successfully explain radiation and its basic effects to you. Please leave any questions, comments and corrections in the comments or send me an email.

Post edited 4/10/11 to clarify explanation of a radionuclide half-life

Written by Hanner

April 6, 2011 at 1:32 am

Posted in News

Baby eagles, now on webcam

Right now there are over 150,000 people watching a Bald Eagle nest in Decorah, IO with me over webcam.

Isn’t the internet wonderful?

Join the cool club and look at some cute/ugly baby birds (or just the momma eagle nesting) with us on ustream

UPDATE: According to Wired, there is still another chick  that hasn’t hatched yet! And it will probably hatch within the next 48 hours! You know what that means: NO SLEEPING. NO GOING OUTSIDE. I hope it doesn’t hatch during my commute…

Written by Hanner

April 5, 2011 at 12:11 pm

The danger of appealing stories: anecdata, expectations, and skepticism

Image: DFID/Russell Watkins

This lovely image was taken by Russell Watkins in Sindh, Pakistan, and I was directed to it by a brief article in New Scientist. Reporter Seil Collins:

Covered in spiders’ webs, these cocooned trees in Sindh, Pakistan, are an unexpected result of floods that hit the region in 2010.

To escape from the rising waters, millions of spiders crawled up into trees. The scale of the flooding and the slow rate at which the waters receded, have left many trees completely enveloped in spiders’ webs.

Although slowly killing the trees, the phenomenon is seemingly helping the local population. People in Sindh have reported fewer mosquitos than they would have expected given the amount of stagnant water in the area. It is thought the mosquitoes are getting caught in the spiders’ webs, reducing their numbers and the associated risk of malaria.

I love this idea. My friends have been passing it around google reader, and it seems to make a lot of sense: More spiders, more webs, more dead mosquitoes in webs, fewer mosquitoes, less malaria. Bing bam boom.

The problem with it: It’s entirely based on anecdata. Anecdata has been my favorite word for about six months now, as well as a topic of fixation for me. It describes information from compiled from a number of agreeing anecdotes, stories, or items of hearsay — “psuedo-data [sic] produced from anecdotes” in the words of urban dictionary. Hearing that multiple people have made similar observations or had similar experiences can clue you into a trend, but hearing a lot of stories doesn’t prove anything. Storytelling is subjective and malleable, not the qualities of good data.

I haven’t been able to find a single scientific source for this mosquito/spider/flood story, though I’d give you a double high-five if you could find one for me.

So what’s the deal with data? We humans look around at our world, make observations, connect them, and use our rationality to draw reasonable conclusions. The story behind the photo makes sense: A number of separate correlations fit together. Who am I to say that we need SCIENTIFIC DATA, free from bias, to speak any kind of truth? After all, the chance to collect baseline data about mosquito and spider populations, average web coverage, mosquitoes per inch of web, etc. has passed and now we can only look back and try to remember what it was like before.

The problem with memory: It changes based on new information. And the problem with stories: They are borne from preconceived expectations.

I recently spoke with Timothy Mousseau, a biologist at the University of South Carolina, for The Scientist about the ecology of Chernobyl. If you scroll through media coverage of this topic, you’ll find many references to the Chernobyl site, which has received the highest level of radiation to date, as a wildlife preserve, one that has finally been able to thrive now that humans have left the area.

Mousseau, however, says this is a perfect example of anecdata. (Well, actually, I was the one who used the word. He thought it was very funny and I was the happiest.) Visitors go to Chernobyl expecting a wasteland, and instead they see the plants and animals that have returned in the past two decades.  These people aren’t liars — they just can’t help but exaggerate. The visitors went in with expectations about what they were going to see, and when the reality was so drastically different, they went back home and told stories about the booming wildlife, even if it hadn’t actually returned to pre-radiation standards.

But many scientists, Mousseau included, have done a great deal of ecological research at Chernobyl and have found decreases in the number and diversity of many taxa, decreased sperm counts and brain size, and physical mutations, particularly in Mousseau’s specialty species, the barn swallow. (I’m going to write up more detail on this over the weekend, do not fear!)

This story of the thriving of wildlife in the absence of humans at Chernobyl, despite the nuclear fallout, is so appealing. It’s got the perfect ingredients: It’s a bit counterintuitive, but after a moment of thought, the pieces fit. “Ohhh, people were worse for the wildlife than radiation! Thank god this nuclear disaster happened and got rid of all the people so the animals can live in peace!” And as an added bonus, it lets us feel a little better about a terrible incident. It’s really no wonder the media clung to this story — but it’s probably not true. It’s just an instance of storytelling being interpreted as data, despite its contamination with human inference and expectation.

That’s what makes me nervous about this flood/spider/mosquito story. It has very similar appeal: The bit of surprise that a flood could decrease malaria, the “ohh” moment when the patterns seem to stack up, and, once again, a bit of good-feeling about a situation that was disastrous for many people.

Oh yeah, and that the reports are totally anecdotal, made by “people in Sindh.”

I want to believe it! It’s beautiful and makes me feel good inside! But the stories that are the most appealing are probably the stories that we should be most skeptical about. And they are also the most dangerous because they are the ones that will be retold over and over.

Written by Hanner

March 25, 2011 at 12:57 pm


There are many people in my life who think it’s strange that I like to meet up with my online friends in real life. “What if he/she is an axe murderer?” is a common remark. And it was very strange at first: The first time I met Bora I basically fled the scene because I couldn’t handle it. (Lucky for me, he stuck around for a second night so I had a chance to redeem myself.)

But it really is fun! I mean, we form these communities online of people that share very specific interests. Why wouldn’t you want to hang out with them?

I was lucky enough last weekend to get to spend an afternoon with Noam Ross (great ecology blogger, grad student, and awesome dude // @noamross) — and then last night a group of us got together at a bar in Manhattan and I had some great conversations with people I’ve known, as well as made new friends. (Awww.) I’ll shoot up a note next time we have one of these meetups in case any of y’all want to join in! We don’t bite… well, at least I don’t.

Anyway: I have the list of attendees and it is my duty to share. So here goes.

If I forgot you, i.e. you missed Krystal forcing my list into your face/beer, leave a comment and I’ll update.

Here’s to next month’s #nycscitweetup! See ya there, I hope

Written by Hanner

March 24, 2011 at 9:29 am

Natural history collections in ecological research

Once I dreamed a dream of being an evolutionary biologist.  As I imagined it, I would hang out in a natural history museum, comparing fossils to one another, taking notes on the minute differences, and piecing together the history of life. It wasn’t until a job fair years ago, when I babbled to an evolutionary biologist about morphologies, collecting specimens, and, pretty much word for word, “working in a dusty basement full of drawers of fossils,” that I realized it was an unlikely future.  The scientist looked at me like I was nuts: “Um… that’s not really what I do.  I work with DNA and genomes.”  I pushed him further, but his answer was clear: The job I described did not exist anymore.

Why can't I just hang out and compare the varying shapes of animals in a basement lair? Image: Wikimedia Commons: Haeckel, Kunstformen der Natur (1904), plate 44: Ammonitida

But while the job does not exist (or is a rare find at best), the specimens do. There are still huge archives at museums stuffed with bones, skins, ad infinitum. I am fortunate to have a friend who works at the American Museum of Natural History in New York in the mammals department. When I visited Catherine back in October, she was spending most of her time with the bat specimens, ensuring that they were in proper order and condition.

She gave me a tour of the place and I was blown away: I had always dreamed of walking into a room, stacked ceiling to floor with hippo skulls, and there I was! Catherine showed me the cleaning rooms, where fresh skeletons are picked clean by flesh-eating beetles; slid open a case in which hung tiger skins, as if it were her coat closet; and, by far my favorite, the marine mammal room, with massive whale vertebrae lined up on shelves. It’s funny to imagine a whale complaining of back pain, but there was even a pair of calcified vertebrae among the bunch.

After walking through the maze of rooms and seeing this vast collection with my own eyes, I couldn’t help but wonder: What are these even used for anymore? Certainly, education, but the museum was already packed with skeletons and stuffed animals without this backup. Catherine told me that sometimes researchers try to extract DNA from specimens, but that purpose alone doesn’t seem to make the best use of this huge collection. If taxonomy is now prescribed by genomics, are these collections, compiled and curated over centuries, going to waste?

In the past couple months, I stumbled upon three papers describing three different ways that these collections can be used to study ECOLOGY! (O, be still, my heart!)  The first, in Marine Ecology, online on Feburary 16, 2011, argues for the use of natural history collections to inform us about past species assemblages of areas that haven’t been heavily studied — baseline data. The researchers used Saba Bank, a reef in the Caribbean Netherlands, as a case study, studying coral specimens collected by divers in 1972. In this older collection, there were five species of corals collected that are no longer found in Saba Bank, suggesting that this understudied reef may need greater protection.

This may seem like an obvious use – but the authors note that it’s relatively unexploited. This may be because of poor record keeping, or the difficulty of locating collections from a specific area that have been shipped off to another museum. Another problem is that, if earlier sampling methods weren’t written down, it’s hard to know how representative a collection is of the area. Divers, not scientists, collected the Saba Bank specimens, so they may not have been trying to take note of all the species there at the time. But finding five species that survived there previously but don’t now is very useful information, no matter the completeness of the collection.

Certain organisms can provide information about their growth through growth rings, which makes their presence in natural history collections useful for learning about environmental conditions. Robert Scott is remembered for failing to reach the South Pole before Roald Amundsen – and part of the reason he was so slow is that he was so busy collecting specimens and taking measurements for SCIENCE. During his 1901 and 1913 expeditions, Scott collected Cellarinella nutti, a bryozoan that develops growth rings. Because this species was collected throughout the twentieth century, scientists were able to date the rings based on collection date, and create a timeline of relative growth: did the bryozoans grow significantly more in one decade than another?

The scientists found no change in growth between 1890 and 1970, but a sharp increase since the 1990s, as they published in Current Biology on February 22, 2011. Based on studies in related species, they think that this growth acceleration is either related to (a) greater production of phytoplankton, the food chain base or (b) a switch in the dominant species of phytoplankton, which could alternatively be more nutritious, speeding their growth. If they’re correct, it means that these museum specimens provide evidence for a recent increase in carbon storage on the seafloor in the Antarctic.

A chicken infected with avian pox with lesions around its beak and eyes. Image: Wikimedia Commons: Roman Halouzka

Natural history specimens can also be useful for tracking the development of disease in an animal population. Avian pox is caused by a DNA virus (the aptly named Avipoxvirus) that causes lesions either externally, on feather-free areas, or internally, in the mouth, windpipe and lungs. Beyond the metabolically draining effects of the virus, the pox symptoms can cause trouble feeding, cleaning and breathing. The virus is carried by mosquitoes and has been linked to the extinction of Hawaiian bird species.

Avian pox has been identified recently in the Galapagos islands, affecting mockingbird, warbler, and finch species that are only found there. To figure out when the virus arrived to help trace the progression of the infection, scientists used natural history specimens. Digging through past collections, the researchers selected birds with lesions like those found on avian pox victims, and looked for viral DNA to confirm that these lesions were caused by the virus. Their research, published on January 13, 2011 in PLoS ONE, reports the earliest specimen with avian pox they found was infected in 1898, and that the infections generally followed the pattern of human colonization. This suggests that the virus has been spread not by mosquitoes moving between islands, but by chickens and other pox-carrying fowl brought by settlers.

These perhaps unexpected uses for natural history collections — to reconstruct species assemblages, extrapolate climatic or ecological variability reflecting growth, or trace a disease through a population — should force scientists to rethink their collection methods. Historically, these collections were created to answer a simple question: What species are out there? As a December 2010 paper in the American Journal of Botany notes (hat tip to Colin Schultz), this mindset often leads to (a) oversampling of rare species, as just one or two specimens can misrepresent their abundance proportionally and (b) undersampling of common species, since just a couple specimens will do.

But gathering fully representational collections is easier said than done. These are real people out in the field, digging in the dirt or seafloor and may not have the space or energy to haul back many examples of a single species. Plus, you can go too far in the other direction; there is also no need to destroy the ecosystem for the sake of fair sampling!

But it does make clear that the age of DNA and genomics does not exclude the need for sampling. To ensure that past collections remain useful as ecological tools, scientists need to keep sampling for the sake of future science.

Edit: Fabulous commenters leave links to relevant articles! They each get a gold star sticker

  • Tracing the history of the parasite Wolbachia in butterflies using museum collections
  • Utilizing museum specimens to map deep sea creatures
  • Using bivalve fossils to study the latitudinal diversity gradient extending from the equator

This post was chosen as an Editor's Selection for>Barnes, D., Kuklinski, P., Jackson, J., Keel, G., Morley, S., & Winston, J. (2011). Scott’s collections help reveal accelerating marine life growth in Antarctica Current Biology, 21 (4) DOI: 10.1016/j.cub.2011.01.033

Hoeksema, B., van der Land, J., van der Meij, S., van Ofwegen, L., Reijnen, B., van Soest, R., & de Voogd, N. (2011). Unforeseen importance of historical collections as baselines to determine biotic change of coral reefs: the Saba Bank case Marine Ecology DOI: 10.1111/j.1439-0485.2011.00434.x

Parker, P., Buckles, E., Farrington, H., Petren, K., Whiteman, N., Ricklefs, R., Bollmer, J., & Jiménez-Uzcátegui, G. (2011). 110 Years of Avipoxvirus in the Galapagos Islands PLoS ONE, 6 (1) DOI: 10.1371/journal.pone.0015989

Steege, H., Haripersaud, P., Banki, O., & Schieving, F. (2010). A model of botanical collectors’ behavior in the field: Never the same species twice American Journal of Botany, 98 (1), 31-37 DOI: 10.3732/ajb.1000215

Written by Hanner

March 2, 2011 at 12:41 am

Transitioning into “real” science journalism

In which Hannah treats her blog like her livejournal circa 2003.  Livejournalism — reflections on being a blogger-turned-journalist.

Two-and-a-half weeks ago, I started interning at The Scientist magazine.  One day I was a scientist, and then decided to leave it all to try my hand at writing about science for a living.  I really didn’t know what to expect, but as the start of the internship crept toward me, I started to become afraid.

My only writing has been on the web, with unlimited space and freedom of form.  I knew that, writing professionally, I would no longer have the freedom to wax philosophical and provide pages of background, as I am wont to do.  Would I be forced to play into hype?  Bend or even break my principles?  Would I leave completely jaded, turned off from science writing altogether?

None of my fears have been confirmed thus far; in fact, the past weeks have been both amazing fun and full of learning.  In each story I’ve covered, I have been able to see the hype point but have always pushed it far, far away from me.  (And I even laugh a little when I see the story distorted elsewhere — that is, before I start crying for humanity.)

I’ve spent the last couple days researching a news story about a PLoS ONE paper about human contamination in databases of genomic sequences that went up tonight.  I was absolutely fascinated by the topic.  The second I spotted the paper, I contacted the scientist, Rachel O’Neill, to hear from her the story behind her research.

Let me tell you — once you start talking to scientists about their work, you can never go back.  There’s really nothing better than to hear what they care about, why they did the work, and, of course, to get the details of the methods explained without having to read wikipedia articles on various genetics tools just to get a sense of it.  It is the most fun part of the job (and also the part I was most afraid of).

After I talked to Rachel, I needed to get a second and even third source to read the paper and let me know what they think.  A scientist can’t help but give a biased account of her own work, after all.  I tried to contact a number of people who work in large-scale genomic sequencing, but no one was willing to give me an interview.  Maybe I picked people who were too big name and above puny me; or maybe the story seemed a bit too controversial and researchers didn’t want their names tied to it.  Either way, I was struggling, and I needed help.

“I have tons of scientist friends on the internet!” popped into my head.  It seemed strange, like I was crossing an illegal boundary between my life as a “real journalist” and a blogger.  This effect is particularly strong for me considering that I’m a huge idealist and can’t escape my view that the world is a meritocracy.  I need to make it as a journalist on my own, without my bloggy friends!  Right?

Nope.  I needed help so I contacted Jonathan Eisen of the Tree of Life, a big-shot genomicist, open access advocate, and evolutionary biologist.  (Did I mention that I might be his #1 fan in a creepy internet way?  Hi, Jonathan! What’s up?)  I learned a ton from him during our talk and it was such a joy to speak to him as he biked across campus (in the wind – what a champ!).  I felt a little strange about it, again like I was breaking some rule because he, like, retweeted me one time or something.  Was I being biased by talking to him? was the thought running through my mind.

When reading the news later it struck me that Monday’s news on a lateral gene transfer between humans and gonorrhea could just be an instance of contamination – an idea that was confirmed by Eisen.  I frantically emailed my boss (Literal: “This could be REAL SCIENCE JOURNALISM, gritty like in the movies!” to which she responded, “I’m confused.”  A little over-excitable, perhaps?)  I emailed Rachel O’Neill about it, but didn’t know how to proceed further.

So, with a sigh, I settled down to read my Research Blogging RSS feeds in the morning.  And what did I come across?  A blog post with the title: “Human DNA in bacterial genomes? Yes? No? Maybe?”  Could this be a dream come true?  I went to the blog and, sure enough, it was written by a genomicist, Mark Pallen.  I emailed him immediately, and later called him up to discuss whether the data in the gonorrhea paper definitively proved that there was no contamination in the database.

I wrote up the story, had a blast doing so, and now it’s on the front page of the website.

For all the fighting I’ve done with myself to avoid being biased in choosing my sources, maybe Jonathan and Mark deserve to be chosen.  They are active communicators, expressing their desire and ability to explain science on the web.  Is that really a bias?  Isn’t that really just.. a logical choice?

In which case… shouldn’t the science blogging community, and Research Blogs in particular, be a goldmine for journalists?  It’s basically a list of scientists (and others.. but many scientists) who want to talk about what they’re doing, make a point to keep in touch with what’s happening in their field (and others), and whose work you can evaluate before even speaking with them.  Is this biased reporting?  I don’t think so – unless they’re your friends, that is.


The second I posted my story, I looked at twitter and saw that Ed Yong had posted a similar story, gonorrhea and all.  But it wasn’t the same story – and that’s because, in the end, blogs do have a win over more mainstream journalism.  I mentioned word count on twitter, but really it’s the story format.

If you’re trying to directly communicate basic information about a new science article, you’ve gotta do it at the beginning — or at least that’s the current practice.  And I do understand the reasoning behind it: if people don’t have time to read the whole article, at least the kernel is provided up front so they can leave learning something.  It also is a good way to get the news out fast; the beginning is the hardest part to write, and by having a formula, most of the thinking is already one: summary of research, implications, outside source quote.  Then you can zoom out and back up.

But because of that, I can’t write the science like a story, or not with the same flow.  I can’t start out with an anecdote about how the scientists started studying the topic, a funny quote, a philosophical anecdote, or anything else.  Scientific research IS a story – as I’ve written elsewhere – a story of how the research progressed, the interests of a person who happens to be a scientist.  The best science writing plants curiosity and leads the reader to ask the same questions the scientists did.

But the news model persists because it’s modelled off of other fields, or sets an easy demarcation of what is worth covering.  “It’s new so we’d better write about it.”

I do believe that journalism and the media are changing for the better, and that a lot of it has to do with blogs and writing online.  Freedom of space and form lead to more interesting stories, better stories.  Right now science journalism tries to frame science to make it a story — let’s reveal this bias, or let’s talk about how xyz new finding has changed the world.

But science doesn’t need framing; it already is a story.

Even if right now I’m constrained by format, I’m not shaken – I still want to continue in science journalism more than anything.  Not only for the joy of it – but if you want to make change, you have to play the game for a little, as I learned from SLC Punk.  (Has this film guided anyone else’s worldview? Please say I’m not alone!)  Maybe one day I’ll edit a magazine and I’ll throw away the formula and get to test whether it’s successful.  But I need to get there first.

…in my dreams right?  Didn’t I say I’m an idealist?

Anyway, enough for tonight.  Here are the articles I’ve written for The Scientist so far if you want to check them out.

  • 3rd Feb 2011 – New mosquito identified: on a group of mosquitoes that hasn’t been targeted – or even identified – in the fight again malaria in sub-saharan africa
  • 10th Feb 2011 – Cellular chaos fights infection:  why disrupting RNA degradation could create antibiotics
  • 14th Feb 2011 –  The mouse is not enough: early development differs between mice, the standard model organism, and cows, further encouraging scientists to study multiple model organisms
  • 16th Feb 2011 – Contaminated genomes: human sequences have been found in over 20% of sequenced non-primate genomes in databases

(I know – I still can’t write a title for my life.  Sue me!)

Written by Hanner

February 16, 2011 at 11:57 pm

Posted in My life, Reflection

Tagged with

The many relationships of leaf-cutter ants

Are those little leaf scraps on the ground? Or is it a line of leaf cutter ants (Atta cephalotes)? Photo taken at La Selva Biological Station, December 2008 by Hannah Waters

Trying to capture the movement of a colony of leaf-cutter ants in a single photo is nearly impossible in my (amateur) experience.  The queues of ants follow a worn-down trail in the ground that they themselves made with the impact of their little ant feet.  There are ants moving in both directions, between the food source and their nest, but you rarely see them run into each other.  (Though small ants, minima, will hitch rides on another ant’s leaf.)  It’s an organized flow of ants and materials – but a photo can only capture the single frame, as if it’s just bits of leaf littering the ground.  The sense of movement is lost.

But that’s only the the frustration if this is the aspect of ant symbiosis you’re trying to capture: the leaf cutter ants collecting foliage to feed to their cultivated fungus. What if it’s a different symbiotic relationship you’re interested in?

BOOM! Image by mass spectrometer to measure the amount of an antibiotic, valinomycin, on a leaf cutter ant, Acromyrmex. by Schoenian et al. 2011.

Leaf cutter ants, of the genera Atta and Acromyrmex, live in huge colonies and can form nests more than 30 meters in diameter.  They’re most noted for their agricultural behavior: they harvest leaves (and can defoliate entire trees in the process) which they bring back to their nests to feed their mutualistic fungus (of the family Lepiotaceae), which acts as a food source for the ants in exchange for the food.

Imagine being in that nest, inside a cavern full of warm, wet fungus.  Most organisms would be looking forward to gorging on this food source, or to growing there themselves.  The ants meticulously clean their fungus gardens and even secrete an antimicrobial acid to keep themselves from bringing in outside visitors, but is that enough to fend off the various microbial and fungal intruders?

In 1999, Cameron Currie (whose ant colony has a twitter account) identified a microbe (Streptomyces) living on the ants’ bodies that produces an antibiotic chemical.  He found this same microbe living not just on one, but many leaf-cutter ant species, including two genera of fungus-growing ants that evolved earlier than the leaf-cutters Atta and Acromyrmex we know and love.  This microbe produced an antibiotic that was very potent against a common garden-invading fungus, Escovopsis.  So it seemed that this was a 3 way mutualism: the ant, the fungus it feeds on, and the microbe that helps protect the garden.

Is anything in biology ever so simple?  The hunt began to find more bacterial antibiotic-producing symbionts.  Scientists have found many more symbionts and garden parasites, revealing the complexity of this ecosystem.  But the microbial symbionts aren’t always masked superheroes protecting the fungal garden: their antibiotics can also do harm to the farmed fungus itself.  Additionally, if there are many species of microbes around, an evolutionary arms race can emerge in which the microbes try to outcompete one another, creating stronger and stronger antibiotics which could be harmful.

Instead of simply listing off the species of microbes they discover on ants, Dieter Spiteller and his lab have been working to identify the antibiotics they produce.  This approach allows them to more easily identify what antibiotic types work on what pathogens and parasites and see what combinations of antibiotics show up together.  After all, the ants don’t care much about what species of microbe lives on them: only the benefit of the antibiotics.

Many of these microbial symbionts are not well-studied, if at all, so figuring out what type of antibiotic they are producing is a bit of a trick.  In their recent paper, the researchers used the evolutionary relationships of the symbionts – constructed using 16S rDNA sequences, which are commonly used to measure the “closeness” of two species – to find their closest relative that had already had its antibiotic identified by scientists.  This allowed them to narrow down their screen to look for the antibiotics that were most likely being produced by each bacterial species instead of having to screen for ALL of them.

They identified many types of antibiotics that fell into three main categories:  antimycins, valinomycins, and actinomycins, the latter so toxic that they aren’t used as antibiotics in humans due to damage to surrounding cells.  Then they tested the effectiveness of each antibiotic against a variety of pathogens and parasites that could endanger the nest: fungal pathogens of the gardens and insects, the common soil bateria Bactillus subtilis, microbial isolates taken from the ants and garden, and even the mutualistic fungus itself, Leucoagaricus gongylophorus.

The antibiotics varied in their strength and specificity.  Unsurprisingly, the most potent was the combination of the three – thus biochemical and microbial diversity is quite important to the success of these ants.  However, the antibiotics can have detrimental effects on other microbes living on the same ant (in particular actinomycin).  But this competition encourages the selection of stronger antibiotics in other species, which is beneficial to the ant and thus the symbiosis overall.

And that brings us back to that second image above: a visualization of the valinomycin distribution on a single ant.  As you can see, it’s pretty widespread – and is found more regularly in a high concentration than in the fungus gardens.  This makes logical sense: an ant would want to kill as many pathogens as possible BEFORE it brought the leaf into the nest.  But it also keeps the antibiotics from killing off too much of the ants’ fungus food.

To sum up: I just wrote a post about antibiotics produced by bacteria, which are competing for space on the back of an ant.  This ant climbs trees, cuts down leaf pieces, and carries them back to its nest to feed to a fungus which it then eats.  The antibiotics produced by the bacteria on its back keep pathogens at bay – protecting the fungus garden, thus the ant, and thus the bacteria. Phew! Currie, C., Scott, J., Summerbell, R., & Malloch, D. (1999). Fungus-growing ants use antibiotic-producing bacteria to control garden parasites Nature, 398 (6729), 701-704 DOI: 10.1038/19519

Schoenian, I., Spiteller, M., Ghaste, M., Wirth, R., Herz, H., & Spiteller, D. (2011). Chemical basis of the synergism and antagonism in microbial communities in the nests of leaf-cutting ants Proceedings of the National Academy of Sciences, 108 (5), 1955-1960 DOI: 10.1073/pnas.1008441108

Written by Hanner

February 8, 2011 at 10:20 pm

Carnal Carnival: Body Odor Edition!

Welcome to the 6th edition of the Carnal Carnival, a blog carnival founded by Bora Zivkovic and Jason Goldman, dedicated to celebrating the traditionally gross in the animal world.  Previous editions have featured poop, vomit, decay and orgasm (which is less gross, but still pretty taboo).

This month of January 2011, the carnival features BODY ODOR!

I'm an artiste; don't judge

You know … when you go to the gym and there’s that one guy, shirtless and reeking of garlic, who happens to be on the treadmill next to you and you nearly pass out.  Or maybe it’s your best friend and, after months of avoiding having a conversation with her about her overwhelming odor, you just buy her deodorant for her birthday.  The smell of B.O. is imprinted upon each of our minds – a stench that sometimes makes us question why we have the ability to smell in the first place.

What is smell and why would we evolve this sense?  What we think of as smell – sniffing odors through our noses – is just a form of chemosensing, found in bacteria, ants, dogs, and, yes, humans.  We have chemoreceptors in our noses that pick up chemicals in our environment and interpret them.  Bacteria use chemosensing to pick up on cues in the environment, molecules of poison or food for example, and can then move towards or away from them.  Ants are well known for their pheromone trails which can alert other members of their colony to danger or to a food source.

The Search by xkcd

In a similar vein, humans have retained their sense of smell to identify food and poisons.  Because rotten food, such as the “smelly dead” illustrated by Viktor Poor of Stripped Science below, gives off such a rank smell and can also make us sick, we can learn to avoid poisonous food based on smell.  But that’s not all this sense does.  We like to think that we are far mightier than ants and that we have control over all our decisions based on mind and intellect alone.  But just like the ant, we also communicate messages to each other through pheromones given off in our sweat, our body odor, that we interpret without realizing it.

Drawing by Viktor Poor of "Stripped Science"

The Smell of Fear

Pounding heart.  Sweaty palms.  Sudden inability to speak.  Enhanced athletic ability.  These are all human reactions to fear.  When you’re scared or anxious or nervous, you feel them to your core – however, those around you might not be aware that you are so scared, much less why.  Thus there is a benefit to be able to communicate this emotion to the people around you, so that they can also be aware, alert, and ready to react.

Since there is not yet evidence of telepathy, sense of smell is the obvious way for individuals to communicate with one another non-verbally.

  • Does sweat produced when a person is anxious make others who smell it more likely to take risks? See this post at BPS Research Digest by Christian Jarrett
  • Can the smell of sweat produced by subjects in horror (watching horror films) cause others to be more likely to see threats where there aren’t any? See Neurocritic‘s post, “I Know What You Sweated Last Summer”

B. O. is sexy?

I have a friend who doesn’t shower too frequently.  Whenever his hair is looking a little greasy and he starts to smell a bit funky, someone will often joke to his girlfriend, “how do you put up with it?”  He’ll then stick his armpit in her face and, with triumph, yell, “She loves my smell!  She can’t get enough!”  Is there any truth to this?

  • Can a woman determine whether a man is aroused just by smelling his sweat?  See posts at both the Neuroskeptic and Christie Wilcox, at her old site
  • Can you identify your partner based on scent alone?  And does this ability vary depending on how “in love” she is?  See this post at Christie Wilcox’s site at Scienceblogs
  • Could there be another explanation for my friend’s cocky behavior? Scicurious of Neurotopia presents an interesting study correlating the attractiveness of a man, rated by women, with his self-evaluation of his own smell

For a great overview on this topic, read Jesse Bering’s post on his Scientific American blog, “Bering in Mind,” Armpit Psychology: The Science of Body Odor Perception.

That’s just rank!

Sometimes there’s nothing else to say but that.

  • How do you deal with people who have bad B.O. in public spaces?  Christina Pikas writes about B.O. in public libraries
  • Morning breath.  We all know about this particular breed of B.O. James Byrne of Disease Prone writes about this, and the broader bad-breath diagnosis of halitosis
  • People aren’t the only ones who can sense and have to deal with the stink of one another.  Read about how elephants can differentiate between different human ethnic groups based on smell alone on Ed Yong’s Not Exactly Rocket Science

To learn more about the evolution of pheromones, I recommend Dr. Kara Hoover’s recent review in the American Journal of Physical Anthropology, “Smell with Inspiration: the evolutionary significance of olfaction.”

Thanks for reading, and I hope you learned a thing or two about the science of human stench.

To end, I’d like to share the greatest human-produced smell of all: The Smell of Teen Spirit

Written by Hanner

January 24, 2011 at 10:01 pm