Flightless Birds

Flightless birds are an evolutionary puzzle. The most befuddling aspect of these seemingly-related animals is their dispersion across far corners of the earth, because, well, they’re flightless.

Two opposing ideas seek to explain the far-reaching origins of these birds. In one, Charles Darwin suggested that a common ancestor flew to new locations, where it then lost the ability to fly. The second theory proposes that flightless birds split away from each other on diverging continents. The discovery of three separate flightless ancestors, dating before Gondwana—a super continent that comprised most of the current the Southern Hemisphere—supports the second theory.

However, several years after this discovery, DNA evidence demonstrated that Moa—extinct flightless birds from New Zealand, which stood up to 3.6 metres high—were closely related to a flying bird in South America, suggesting that they had a flying ancestor.

Last week, Royal Ontario Museum researchers released new information showing that both theories may be right. By analyzing Moa DNA, researchers discovered that the bird started to evolve along several different paths after Gondwana split apart, but at least two ancestral lines were founded later by birds that flew to new locations. This new discovery highlights the nuance of evolutionary biology.

Volcanic Eruptions

Volcanic eruptions start small: gas bubbles form in magma, heat and expand, then finally shatter the surrounding rock with explosive force. Whether these explosions are small and mild, or large and catastrophic, depends largely on the first ten seconds of bubble formation.

This month, McGill Earth and Planetary Science Professor Ron R. Baker, in collaboration with an international team of scientists, examined this phenomenon in the lab, modelling the volcanic bubble formation process in basaltic rocks. After using a laser to super-heat the rock, the team was able to observe the bubbles growing with a specialized X-ray microscope—essentially, an ultra-precise CT scanner. By using the images to measure bubble size and wall thickness between bubbles, they were able to determine the explosive potential of different formations.

Extremely explosive basaltic volcanoes are rare—Hawaiian basaltic volcanoes are considered mild, despite the fact that they can shoot lava up to nine kilometres into the air—but understanding more about bubble formation will allow scientists to start chipping away at the problem of determining what conditions cause these catastrophic events to occur. This should lead to more accurate predictions of volcanic eruptions. Their findings are outlined in a recent paper in Nature Communications.

Global Food Security

Is it possible for the earth to produce enough food to feed its massive, multiplying population, or should we begin our move to Mars? A joint study by researchers at McGill and the University of Minnesota published in the interdisciplinary magazine Nature last month provides hope that humans can stick around if we manage our resources wisely.

Using a broad analysis of global farm production, the researchers compared overall crop yields from both high and low-performing farms in certain regions. Their analysis suggests that using existing farms to their full capacity could bolster global food production by anywhere from 45 to 70 per cent for most crops. This means increased agricultural output doesn’t have to come at the expense of pristine forests and ecosystems.

In addition, the study revealed that increasing productivity will not require an increased use of fertilizer, which is associated with pollution and drinking water contamination. Nitrogen and phosphorous usage, two of the biggest culprits in agricultural pollution, could in fact be reduced by 28 and 38 per cent respectively worldwide, without negatively impacting yields for major crops such as wheat, corn, and rice.

While the study seeks to present a general picture, rather than delving into the details of implementing such sweeping changes, the dramatic findings allow for optimism on this serious and timely (seven billion people and counting) problem.

There is always a sense of child-like wonder that is evoked by staring at that vibrant, multi-coloured silver maple en route to work. Indeed, why trees change their colour during the fall is the kind of question a father might have to answer for his curious five-year-old daughter. Yet changing leaves is such a basic part of our year that many may be quick to overlook it.

All plants rely on photosynthesis to convert sunlight into chemical energy. This process occurs in the cells of each leaf, where chloroplasts turn carbon dioxide and light into sugar for food.

Chlorophyll, a chemical present in chloroplasts, is responsible for the leaf’s green colour, as well as for capturing sunlight and triggering the photosynthetic process. When there is more sunlight, plants produce more chlorophyll to absorb it. This explains why trees are green during the summer.

This green pigment in chlorophyll masks two other pigments in the leaf: carotenes and xanthophylls. Xanthophylls contain oxygen and produce a yellow colour as they absorb sunlight and stabilize chlorophyll. Carotenes contain no oxygen and produce an orange colour. Unlike chlorophyll, the carotenes and xanthophylls are present in the leaf year-round, whereas leaves’ levels of chlorophyll depend on the amount of sunlight it receives.

As the weather worsens and daylight decreases, so do chlorophyll levels in plants. When the seasons change and sunlight becomes scarcer, leaves begin to store their food rather than photosynthesize it. The green from the chlorophyll fades at the end of summer, revealing the yellow-orange hue of carotenes and xanthophylls during the fall.

Interestingly, the redder tones of fall are less easily explained. Biologists know that the red colour comes from anthocyanins—a chemical which, like chlorophyll, is not present in the leaf year-round. Rather, anthocyanins are produced only during the fall, as chlorophyll is broken down.

Its function is less clear. Some hold that anthocyanins act as a kind of sunscreen, protecting nutrients in the leaf from sunlight and keeping it on the branch longer. William Hoch, a professor at Montana State University, conducted an experiment in 2001 using mutant trees that could not produce anthocyanins. He placed them in bright sunlight and cold temperatures, and found that leaves from these trees fell while they were still green.

According to Hoch, leaves are redder when external conditions are harsher. When temperatures are colder and the sun is stronger, a leaf requires more anthocyanins to provide it with the nutrients that keep it on the branch. With less sunlight and more rain clouds, trees need less anthocyanins and are therefore less red.

Leaves’ hues depend on the amount of external stressors; nutrient levels in the soil, pollution, and exposure to sunlight are just some of the elements that determine anthocyanin production. The main debate surrounding anthocyanin is how it responds to these different environmental stimuli. Experts are still at odds over which conditions produce the reddest leaves.

In any case, the spectrum of colours that emerges during the fall does so as green chlorophyll fades, revealing yellow xanthophylls and orange carotenes. Red anthocyanins are produced to protect nutrients and keep the leaf on the tree. Once the leaf runs out of moisture and nutrients, it falls to the ground.

On Halloween, the streets will be filled with children dressed up as witches, vampires and other frightening creatures. For the past fifty years, research has speculated that the myth of one of these monsters can actually be traced back to a medical  disorder.

Vampires are typically characterized by sensitivity to sunlight, pale complexion, and a diet of human blood. Some scientists have speculated that there is a link between these traits and the symptoms of porphyria. It appears that the age-old vampire could have been no more than a victim suffering from this disease.

Porphyria is a collection of related diseases that involve pigments known as porphyrins, which accumulate in the skin, bones and teeth. One of the best-known porphyrins, and the agent of this disease, is heme—the pigment in red blood cells and a component of the oxygen transporter hemoglobin.

Essentially, all versions of porphyria result from faults in the body’s production of this pigment. Heme is made in a sequence of eight steps, each equally important and catalyzed by a separate enzyme, as in a factory assembly line. If any of these steps is disrupted due to a mutation or an environmental toxin, the entire assembly line is halted. As a result, products of earlier steps, including some porphyrin intermediates, can build up to toxic levels.

The problem occurs when these porphyrins accumulate in the skin and other organs. While porphyrins are benign in the dark, they are transformed into corrosive, flesh-eating toxins when exposed to sunlight.

Porphyrins readily absorb both visible and ultraviolet light in order to transfer energy to oxygen molecules. Through this process they form singlet oxygen. Due to its reactivity and interactions with the skin, this derivative of oxygen can cause the symptoms suffered by victims of porphyria.

Along with an acute sensitivity to sunlight, the disruption of heme production means that the body cannot produce enough heme to form normal red blood cells, eventually leading to hemolytic anemia.

The type of porphyria that some researchers believe to have inspired vampire tales is known as congenital erythropoitic porphyria. It’s one of the worst forms of the disease, and causes symptoms such as gum and skin disfigurement.

Dr. Joe Schwarcz, the director of McGill’s Office for Science and Society, examined this connection between vampires and porphyria. In his article, “The Myth of Vampires and Porphyria,” he noted that Dr. David Dolphin, one of Canada’s top chemists, suggested the porphyria victims’ sensitivity to sunlight, and the possibility that receding gum can give the appearance of fangs. He believes this could have led to the creation of the myth of vampires.

However, while there are some links between porphyria victims and the mythological vampire, many aspects of the vampire-porphyria hypothesis do not hold up to scientific scrutiny.

For instance, Dr. Schwarcz mentioned that some researchers have suggested that “[as] porphyria now is treated by injection of blood products such as hematin that will interfere with porphyrin synthesis, at one time victims may have attempted self-treatment by drinking blood.”

Unfortunately, the ingestion of blood on its own, as opposed to the infusion of the pigment and blood product of hematin, would not provide any treatment for the disease.

Nonetheless, while science has yet to come to a consensus as to whether or not the porphyria-vampire hypothesis holds true, it is not uncommon for mythology to be derived from medical causes or natural disasters of the past. People crave explanations for unknown phenomena, and most often these explanations take the form of story and myth. Whether or not porphyria is the link to the creation of vampire stories, it is not unlikely that there were some medical or other natural phenomena that caused the ancient Chaldeans in Mesopotamia—the people to whom the first vampire myth can be traced—to tell tales of such a creature.