What should Stephen Harper know about biology?

I’m teaching again this semester, this time in Bob Montgomerie’s fourth-year course on the history and philosophy of biology. My job is to moderate group discussions and seminars in the tutorials. It will be a lot of work, since tutorials happen every week, but I’m excited at the prospect of using our debate as fuel for this blog.

I started by asking the class to answer three questions in an anonymous survey. First, I wanted them to tell me the most surprising thing they had recently learned about science.

My example of this was the nocebo effect. it’s the opposite of the placebo effect, with a bit of voodoo-witchcraft thrown in: apparently just believing in a negative outcome can be bad for your health. What I found surprising about it initially were the spooky anecdotal accounts of people diagnosed with terminal illness, and then dying within a few months just as the doctors predicted – only to have pathologists later realize that the original diagnosis was in error. Can we think ourselves to death?

But maybe this was a bad example. In general, the power of negative thinking isn’t all that surprising. Why shouldn’t there be a flip side of the coin for the placebo effect? After all, the negative effects of stress and anxiety on health are well-documented by the medical community. For example, this Washington Post article describes a study on blood thinning drugs where doctors showed that just by giving patients a warning about gastrointestinal side effects, you can make it much more likely that they will experience those negative symptoms. Other documented nocebo effects in the Skeptic’s Dictionary range from headaches to allergic reactions. Again, the power of thought to affect us via our own immune systems is perhaps not so surprising.

Voodoo may have lost its magic too: according to this article from Salon, there is some debate as to whether examples of death by curse in tribal societies are really due to starvation and dehydration, since feeding the doomed individual is often seen as a waste of scarce resources. And of course, the medical anecdotes of death by false diagnosis are good stories, but probably not much more than eerie and highly memorable coincidences.

What do the students find hard to believe? Out of 28 responses, 4 had to do with the paradoxical nature of modern physics. There was 1 response on lemmings that was certainly hard to believe, because it was just plain wrong (more on that later, but lemmings do not jump off of cliffs in a form of altruistic mass suicide. That is a myth). The majority, at 14, were on marvels of adaptive evolution (e.g., the complexity of the brain, venomous mammals like the platypus, bowerbirds, examples of rapid evolution).

This is proof that majoring in biology does not diminish the sense of wonder we have about living things. If anything, it probably enhances it. Here are two student responses that sum it up nicely: the “diversity that surrounds us” and “just how much there is out there to learn”. It may be the hardest thing about biology to really wrap your mind around, but it sure is fun to try.

The second question: What should Stephen Harper know about biology?

The most popular category here was the environment, with 13 students listing principles of ecology and environmental science that Harper could use. After that, 4 wanted Harper to have a basic grasp of evolution and natural selection, especially given the strange opinions of his science minister Gary Goodyear. There were 2 shameless requests for more research funding. Sadly, 2 left this one blank – hopefully not because they think Harper doesn’t need any biology. At the other extreme, 1 complained that there is a lot Harper should know about “any matter really”. One student wants him to have “a dangerous idea like Charles Darwin”.

I would tell Stephen Harper that Taq polymerase comes from Yellowstone National Park. Everyone should know this one – I’m sure I learned it during undergraduate, but forgot, only to be reminded of it again recently.

Here’s the story: Taq polymerase is a chemical we use to study DNA. A workhorse of the modern genetics lab, this enzyme makes it possible to turn a minuscule amount of DNA into a much larger sample by rapidly copying the molecules at high temperatures in the polymerase chain reaction (PCR). Countless techniques are made possible as a result: forensic DNA fingerprinting, diagnosis of genetic diseases, unraveling gene functions, sequencing whole genomes, and filling in the branches on the tree of life that describes how all living things are related to one another.

Taq polymerase works at high temperatures because it comes from Thermus aquaticus, a heat-loving bacteria. Up until the 1960s, the temperature threshold for life was thought to be around 73 degrees Celsius (which is the limit for photosynthetic bacteria). However, in 1967 Thomas D. Brock and Hudson Freeze reported finding bacteria that could withstand temperatures a lot higher than that in the hot springs of Yellowstone. This was revolutionary. Years later, when people were working out the chemical procedures necessary for DNA analysis, it was knowledge of the earlier Yellowstone discovery that made efficient DNA copying at high temperatures possible.

I also asked the students what they hoped to get out of the course. Only 1 claimed a good mark, which was surprising for an anonymous survey. Some emphasized novelty: to learn “something new in biology for once”, “something stimulating and eyebrow raising” and “ideas never thought of before”. Others hope to learn some personal and biographical details of the iconic figures in science: “what inspired them” and “what was going through their heads when their ideas were opposing the popular belief of their time”. I hope I can learn from this group about what goes on in the heads of students and the public in Canada.

Reaching the other side, in synchrony

It’s a familiar site on campus here during the first week of class: packs of jaywalkers moving in tight co-ordination, in sync with the flow of oncoming cars. From traffic lights and power grids to stereo sound and cinema, synchrony is so common in our environment that we usually only notice it when it fails. Not so with nature: the examples of synchrony in living things tend to be much more surprising to people studying animal behaviour.

Group courtship displays are a classic example. Think of chorusing songbirds in the morning or calling frogs gathered around a pool of water at night. Readers of my blog on peacock field work might be familiar with lek-mating birds gathered around a clearing to wait for females. Peacock train displays also tend to happen in sync. One traditional explanation for these co-ordinated displays is that, by synchronizing their most conspicuous behaviour, animals might gain some protection from predation1. Another possibility is constructive interference: co-ordinated timing might allow a pair of animals to spread the message farther than either one could on its own2. Two innovative new studies on animal courtship have added to this list. The first, on firefly displays, shows that synchrony might help insects recognize members of their own species by getting rid of visual clutter.

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Honed

We brought home a new kitchen knife from my parents last month. The knife block was full, but Charlie exchanged the new one for what was previously our smallest and dullest. He wasted no time wrapping the old one up in plastic and hiding it from me. My hand naturally gravitates towards whichever tool will fit nicely inside it, even when I’m cutting a monster squash. We have a good arrangement: Charlie keeps the knives sharp, I keep my fingers, and I toss him the odd carrot slice in return.

But could he eventually be replaced by a sea urchin? A new study in the journal Advanced Functional Materials explains how sea urchin teeth never dull or break. In fact, they get sharper with use1.

Most people are probably familiar with sea urchins as the spiny little balls one occasionally encounters on the beach. Evil looking, but mostly harmless, so long as you avoid stepping on them. Sea urchins live in shallow tidal pools, eating algae and other plant material. So why do they need such sharp teeth? Much like their spines, the teeth probably serve a protective function. The urchins use them to chew burrows, often in solid rock, where they can take shelter from predators and waves.

In the current study, a group of physicists and biologists used an arsenal of sophisticated imaging, chemical and nano-scale stress test procedures to investigate the teeth of the California purple sea urchin (Strongylocentrotus purpuratus). Like starfish and sea cucumbers, urchins are members of a group of animals known for their penta-radial, or five-fold, symmetry. They have five teeth arranged in what is known as Aristotle’s lantern.

Aristotle's lantern

Aristotle’s lantern, as viewed from below with teeth closed. From Killian et al. 20111.

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Shark Lady and the convict fish

Who’s weirder: the shark lady or the convict fish? It may seem a strange way to get this blog started again, but it turns out to be quite fitting this time of year when we find ourselves cooped up with relatives of all stripes.

My first encounter with the convict fish was this summer. It was one of those enigmatic creatures that blew all of the biologists in the room away, at one of our regular gatherings to watch the BBC’s Life series. Over images of thousands of tiny fish emerging from a burrow on the sea floor, David Attenborough explained the mystery. This was a swarm of siblings, all offspring of the same pair of adults who spend their entire lives in a tunnel. Each day, the young convict fish head out to forage on plankton around the reef, returning home at night. Biologists have no idea how the parents feed, though, because no one has ever seen the adults leave their burrows in the wild. Attenborough left us hanging, suggesting with intrigue that the young fish might have something to do with it.

Could the convict fish be living off of its own offspring? A bit grim, yes, but also a fascinating biological paradox – perfect for this blog on the stranger twists of evolution, I thought. In nature, it might not even be that unusual. The males of plenty of fish species feed on eggs from their own nests. By taking in extra resources, this might allow them to invest more in future nesting attempts1. In fish with especially large broods, once filial cannibalism gets started it could get an evolutionary boost from the fact that many of the offspring in dense egg masses will not survive anyway2.

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Deep archives: Irreducible beauty

Peacocks and audience at the Toronto Zoo

Were peacocks designed with this kind of audience in mind?

A while back I was searching for images of peacock feathers on Google, and I stumbled upon this article. It’s a piece by Stuart Burgess, an engineer who is head of the Department of Mechanical Engineering at Bristol University, and apparently also quite an opinionated creationist.

Burgess’ idea is that the peacock’s train feathers “contain an extremely high level of optimum design”, so much so that they provide evidence against Darwinian evolution. He thinks that the aesthetic features of the peacock are so complex, so contingent upon each other, that no step-by-step process of evolutionary change could have produced them. He’s right that these ornaments are highly complex, and that selection for this kind of extreme aesthetic feature presents a bit of a puzzle for evolutionary biology. To claim that the extraordinary complexity must be “irreducible”, however, is a big assumption.

The article provides a lot of amusing examples of twisted logic along the way. For example, one of the features that Burgess finds irreducibly beautiful is the fact that the peacock’s train forms a fan-like shape. This is because “the axis of every feather can be projected back to an approximately common geometrical center” – indeed, the body of the bird that grew them!

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Deep archives: Sex “pests” get more practice

Juvenile male peafowl practice their displays

Having finished my field work this year, I thought I’d keep up with this blog by writing about interesting things that other people have seen animals do.

To start: this BBC science news report on the discovery of a “sex pest” seal that attempted to mate with a penguin, brought to my attention by Rob Ewart (the original paper can be found here but you will need a subscription to the journal to read the whole thing).

Apart from the entertainment factor – the abstract to the scientific paper concludes, “we report a case of interspecific sexual harassment bridging the rank of vertebrate class” – there are a few interesting issues here. The first being, why on earth would the seal do this? The authors provide a few possible answers. Apparently these fur seals sometimes eat king penguins, so perhaps by some strange mis-wiring, predatory arousal translated into sexual arousal in this case. Alternatively, the seal may have been too young to find a real mate, desperation leading it astray. Or, intriguingly, the young seal could have been play mating, a form of practice for the real thing later on.

The second issue: why on earth would a scientific journal publish something like this? Is it really that unusual for hormonally-charged animals to make the occasional mistake? This year alone I witnessed a peacock give chase to a human female (with the characteristic “hoot” of excitement that accompanies all mating attempts), and I’ve seen several peacocks attempt the same with guinea fowl and squirrels. All of these events happened with males that were displaying intently but that hadn’t had any peahen visitors in quite some time. Is this paper really such a novel finding, or are the authors just as desperate as the seal?

On reflection, it’s probably important to document these unusual behaviours somewhere, since it would be an interesting outcome if they turned out not to be mistakes after all. Young peacocks, for example, will frequently display their undeveloped train feathers to each other (pictured above). This male-male display may seem futile, but I wouldn’t be surprised if the kind of dancing skill required later in life demands some practice. Similarly, in Costa Rica I remember hearing juvenile long-tailed manakins displaying long after the real mating season had ended, no doubt honing their skills for next year. There is even some evidence that the reason male manakins pair up for their co-ordinated display dances, even though only the dominant member of the pair will get to mate, is for the practice.

The full citation for the seal paper:

De Bruyn PJN et al. 2008 Journal of Ethology 26:295-297.

And two on long-tailed manakin displays:

Trainer et al. 2002 Behavioral Ecology 13: 65-69.

Trainer and McDonald 1995 Behavioral Ecology and Sociobiology 37:249-254.

Deep archives: An instance of spite?

I have seen my first peafowl egg. Laid in the sink of the men’s bathroom, some of the Arboretum staff found it and brought it to me, unsure of what to do with it. The peafowl are overpopulated here and the staff are encouraged to find (and destroy) eggs. I ended up giving this one to Rob’s relatives from Palmdale in the hopes that they could hatch it (they keep chickens and have an incubator).

Perhaps in line with the fact that laying season is upon us, we’ve seen a few quite heated episodes involving the peahens in the last few days. Specifically, I’ve seen a couple instances of females being aggressive towards other females right in front of displaying (and preferred) males. Although this behaviour has been described before, it’s quite a paradoxical thing from the evolutionary point of view since female-female aggression over a presumably unlimited resource (mates) would be entirely spiteful.

I had seen the females in Winnipeg aggressively displaying their tails to each other in front of certain males a few times, but a recent episode here in Los Angeles has clarified the situation. This was, unmistakably, a female trying to prevent other females from mating with one of our top males. Here’s how it unfolded…

Male no. 30 was displaying his tail, with three females in the area: two sitting nearby in a little garden, preening away, and the third seeming to mirror the male while she aggressively displayed towards the preening females.

Peahen-peahen aggression

This went on for several minutes. Eventually, one of the preeners got up and left, and a few seconds later the aggressor lowered her tail and started walking away. Almost immediately, the second preener hopped down from her perch and accepted male 30’s advances right away. This brought the aggressive female literally running back to the scene, but it was too late for her to prevent the copulation. Luckily we managed to photograph the whole thing.

Peafowl copulation

Not sure what to make of it yet, but interestingly yesterday I saw more female-female aggression in front of another one of our favoured males. Our good intentions to work this morning were foiled by some light rain (peacocks don’t do anything when their trains are wet), but hopefully I’ll see some more of this action soon.

Language Instincts: Do animals lie?

Liar

From November 11, 2006

In my last few posts you may have noticed a theme: signals that are used to advertise sex in the animal world are generally thought to be honest ones. In fact, animal communication in general is pretty truthful. There may be different reasons for this: some signals may be impossible to fake (for instance, toad calls may contain honest information about the caller’s size simply because bigger bodies produce lower-frequency sounds). But even when a signal could be faked, the evolution of dishonest signaling is very unlikely. There is a simple reason for this: in the long run it would not benefit receivers to respond to a signal that could be cheated.

This is something that we might find surprising given the amount of deception that goes on in human interactions. Is deception really so rare in animal communication systems? Are there any animals liars?

We have some examples of deceptive communication between different species: for example, ground-nesting birds will fake an injury to draw a predator away from their nest, and some birds in mixed-species flocks will give false alarm calls to increase their own foraging success. Within species, however, the examples of deception are few. We know deceptive communication occurs within a number of primate species. Interestingly, some recent work using ravens has shown that, much like many primates, birds may also be capable of intentionally deceiving conspecifics.

This result came as a bit of an accident during an experimental study on social learning and scrounging in foraging ravens. The researchers provided their ravens with a series of covered plastic boxes that served as food caches (some containing pieces of cheese; some empty). The boxes were arranged in clusters and ravens were videotaped during their foraging explorations. Right from the start, the researchers noticed an interesting pattern between a pair of male ravens: rather than search for his own food, a dominant male relied on a subordinate male’s explorations, following the subordinate male around and eating the food that he discovered.

It eventually became apparent to the researchers that the subordinate raven wasn’t the only one being exploited in this situation. He had developed a strategy to trick his competitor. Whenever the subordinate male found a cluster of boxes containing food, he would quickly move on to a different cluster and start opening boxes there. The dominant male would soon follow, leaving the subordinate free to return to the other boxes and enjoy his snacks at leisure.

The parallels here to primate behaviour are interesting: chimpanzees have been known to walk away from a food site in order to induce other group members to do the same, and then return later to enjoy the food in privacy. Does the ability to communicate deceptively say something special about the cognitive evolution of a species?

You can read the raven study here.

Language Instincts: The evolution of sexual signals

From October 28, 2006

This Thursday Al Uy from Syracuse University came to talk to the Ecology, Evolution and Behaviour group at Queen’s. Al spoke about his research on the ecology and evolution of visual signaling in birds.

Plumage colour in birds is known to be involved in conspecific communication, including the signaling of quality to potential mates. In many species, females can gain information about the condition or health of a certain male just by assessing the colour of his feathers. Sexual selection for honest signaling is often implicated in the evolution of brightly coloured plumage, much like the evolution of the peacock’s tail described in my last post.

Al Uy is interested in understanding how sexual selection might contribute to the speciation process, since changes in sexual signals can lead to reproductive isolation between two populations. He pointed out that this idea originated with Darwin, who noticed that often the only difference between closely related species is a sexually dimorphic trait such as male plumage colour. To understand why this might be, Al studies the plumage colour of small birds called the bearded manakins with an interesting mating system: the males gather at display sites called leks, where they clear an area of the forest floor and dance to attract females. There are several subspecies of bearded manakins, all with striking differences in male colouration (whereas the females are all plain and look alike). Here are two of the manakin subspecies Al works on (golden-collared and white-bearded males):

Golden-collared manakinWhite bearded manakin

The signal function of manakin beards

Al began his talk by discussing his investigation of the signal function of colour in the golden-collared manakin, which formed the groundwork for his research in signal diversification. Al and his students have found that the yellow colour of the male ‘beard’ plumage functions as a signal of male quality that females assess during male dancing displays, since males with brighter yellow beards tend to be larger, have higher display rates, and obtain more matings than their dull-bearded counterparts.

Al also tested whether the brightness of the male plumage translated into conspicuousness from the point of view of the female manakins. He used a model that took account of avian perception, ambient light during male display, the reflectance of male plumage and the reflectance of the visual background during display (the dancing court). Consistent with the predictions of sexual selection theory, male conspicuousness as calculated by this model was related to male mating success. In other words, more conspicuous males obtained more matings. Unexpectedly, Al found that the darkness of the visual background was actually more important in explaining the variation in mating success than plumage reflectance, suggesting an important role of the visual habitat in shaping conspicuousness and the evolution of lekking. Al thinks that the lek mating system might have arisen from males becoming more competitive for the specific areas of the forest providing the best visual background for display. In the near future Al plans to test this idea by comparing the reflectance properties of the lek habitat with other areas in the forest.

Why are there so many beard colours?

The next part of Al’s talk focused on his main research interest: understanding what factors might promote the diversification of sexual signals like manakin beard colour. The basic hypothesis he is testing is that changes in the visual habitat can drive the diversification of visual signals. In order for plumage colour to be conspicuous (and therefore most effective as a signal) it needs to match the available light, contrast the background, and be tuned to the receptivity of the target individuals (females). Changes in any of these factors could have promoted the evolution of the four different male colour types found in the bearded manakins.

Al plans to test this hypothesis in several ways. First, he will examine whether or not the evolution of retinal physiology might be driving the diversification of male colour. He plans test this idea by comparing the abundance of retinal cones between the different manakin subspecies. If females from different subspecies have retinas that are optimally sensitive to the beard colours of their mates, then changes in female perception might be driving changes in male beard colour.

Al is also testing his ideas about colour diversification by studying a hybrid zone of golden-collared and white-bearded manakin populations. This is an area of Costa Rica where a river divides populations of the two manakin subspecies, although the yellow plumage trait (found in golden-collared manakins) extends slightly into the white-beaded population. One hypothesis Al is currently testing is whether this trait introgression has occurred because yellow plumage is intrinsically more attractive to the manakin females, although at this point he can only speculate as to why this might be. Al is testing this possibility by examining mate choice in the area where both yellow and white males are competing for the same mates.

The other question Al would like to answer is: what stops yellow males from sweeping further into the white population? It seems unlikely that the river is a physical barrier isolating these populations since birds are certainly capable of crossing it. Instead, Al is looking into the possibility that a change in the visual habitat on either side of the river is maintaining the separation between these two populations. In other words, white birds in succeed in their habitat (despite some introgression of yellow males) because white is the most conspicuous and best colour for displaying in that habitat.

Although Al’s talk was a bit long, it was enjoyed by the audience at Queen’s for telling a complete story without being overly technical, and some went so far as to claim it was the “best talk ever” (Dev Aiama). You can read more about Al Uy’s research here.