How Do Astronomers Find Exoplanets?

Artist's conception of exoplanet Kepler-16b. Image courtesy NASA/JPL-Caltech/R. Hurt.
Artist’s conception of exoplanet Kepler-16b. Image courtesy NASA/JPL-Caltech/R. Hurt.

By: Sara Knight
BU News Service

Last month astronomer Erik Petigura announced it was likely that our galaxy may have up to 40 billion Earth-like, habitable exoplanets swirling around their Sun-like stars. Petigura’s conclusion, which resulted from his analysis of Kepler satellite data, marks a huge milestone in the search for exoplanets – a field that has experienced a rapid expansion in the past decade. The ultimate goal of this extra-solar quest – to find planets with conditions able to support life as we know it – is only attainable if researchers can not only locate these other worlds, but discern their composition. Given that the nearest exoplanet is 4.37 light-years, or 26.22 trillion miles, away from Earth, it is no simple task. So how do researchers find and analyze alien worlds?

It comes down to tenacious observation and a lot of math. First, astronomers must set a satellite or telescope to record a given patch of space – for example, the Kepler satellite focuses on an astral window of about 100,000 stars. Then they wait for minute fluctuations in the amount of light a star gives off, which indicates a body, maybe a planet, passing in front of the star. Researchers confirm the light-blocking object as an exoplanet only after noting that the light fluctuates in a regular pattern, which can take years depending on the length of the planet’s orbit.

Once the light-blocker is verified as a planet the researchers ascertain its volume and mass. Luckily for them, finding the planet’s volume is relatively straight-forward – the amount the star’s light dims as the planet passes by denotes its size. Finding the planet’s mass is trickier: researchers must determine the strength of the gravitational attraction between the planet and star. The larger the attraction, the more massive the planet. The star itself is also “in orbit” around the center of mass between itself and the planet – it is just so massive that its orbit is more of a wobble than a proper ellipse. As the star wobbles, the frequency of its light changes in the visible spectrum – a phenomenon known as the Doppler effect. By observing these fluctuations, astronomers can figure out how much a star wobbles, and therefore the mass of its orbiting planet.

Artist's conception of exoplanets in the Milky Way. Image courtesy Wikimedia Commons.
Artist’s conception of exoplanets in the Milky Way. Image courtesy Wikimedia Commons.
After obtaining the figures for the planet’s volume and mass, finding the planet’s density is as simple as dividing the mass by the volume. Once astronomers figure out the density, they can extrapolate the sorts of materials that may make up the world. For example, an exoplanet with an extremely high density is probably composed of heavier materials, like rocks and metals.

In 2010, astronomers began using light frequency analysis not only to find the mass of the exoplanet, but also to infer its atmospheric makeup. While the planet passes between the star and their observation point, the chemicals in its atmosphere will give faint light signatures, which astronomers analyze using a chemical spectroscope. By noting which elements shift in the star’s chemical lineup when the planet passes by, they can infer the chemicals present in the exoplanet’s atmosphere.

So far, astronomers have found a huge variety of alien planets – some made mostly of metal and with 20 Earth-hour years, others made mostly of super-hot gas and that have silicate glass particles as rainfall. While the exoplanets with what we on Earth would consider extreme conditions are the coolest to read about, the ones that are able to sustain liquid water most interest astronomers. Those relatively ho-hum planets reside in the habitable zones of their stars – zones that astronomers believe life as we know it in our solar system may exist. And despite the report that there are probably 40 billion of them out there, we have only spotted twelve of them so far. But by remembering the scope of our search this humble figure seems a little less discouraging. After all, we can only focus on a small fraction of space at a time and stars are oriented randomly throughout the Universe – who knows what we’re missing?

The “After the Rainstorm” Smell

By: Sara Knight
BU News Service

After a rainstorm, you step outside to a world transformed. Colors have become darker and more vibrant while everything else seems muted – the normal chitter and chatter of wildlife becomes conspicuous in its absence. Earthworms, normally hidden safe in the soil, suddenly litter the ground, lying bloated and still on the sidewalks. But the most striking transformation is the smell – that earthy, pungent scent is as pervasive as it is unmistakable.

If you look at this picture, you can almost smell it:

Image from Wikimedia Commons.
Image from Wikimedia Commons.

The smell itself actually has a name: petrichor, which is a combination of “petri-,” a Greek base meaning “stone,” and “ichor,” an ethereal fluid that served as blood for Greek gods and immortals. But where does this inimitable smell come from?

It’s a combination of plant oils and the waste product of a soil-loving bacteria in the Streptomyces genus. The oil in question is produced by plants during dry periods – ostensibly as a sort of birth control until more water is available, as it postpones seed germination.

The other culprit, the bacterial waste, is a compound called geosmin. Streptomyces bacteria are important decomposers; as they break down rotting vegetation and other organic material in soil they produce geosmin as a by-product. Geosmin is also behind the earthy taste of beets and the muddy smell of catfish.

During rainfall, the plant oil and geosmin are bled out of their hiding places and released into the air, creating that wonderful distinctive scent.

The World’s End

Image from Wikimedia Commons.
Image from Wikimedia Commons.

By: Sara Knight
BU News Service

Astrobiologist Jack T. O’Malley-James and his team detailed their efforts to predict how life on Earth will end in the beautifully titled study “Swansong Biospheres.” Despite appearances, their end goal is not to depress us with a reminder of mortality and the non-permanence of everything we know and love. Rather, they seek to know what might happen to life here to know what to look for on similar but older worlds out there.

Our sun’s gradual warming and eventual exhaustion of nuclear fuel sets off the ticking clock in the background of the study. One day, the sun will find itself with no more core hydrogen to burn and will be so bummed-out it will collapse in on itself in disappointment (or because of gravitational attraction, maybe). By contracting, the sun will pull in more hydrogen to its center, setting off a rapid chain of reactions – increasing its luminosity and sparking a great expansion. It is at this point our sun evolves from a cute yellow dwarf into a mature red giant. Scientists mark this graduation date occurring anywhere from 5 billion years to 7.6 billion years in the future.

According to O’Malley-James et al. life will already be several billion years extinct by that point. They estimate that the hardiest unicellular life-forms will be able to cling on to our increasingly blistering planet only up to 2.8 billion years in the future, and then only in the highest latitude regions in caves of ice.

This knowledge allows us to search for life on Earth-like planets at different phases of their evolution. O’Malley-James explained to National Geographic: “A planet in a later stage of its habitable development may appear uninhabited if we only look for the signs of life as we know it on Earth today.”

More Great Information on the End of the World and/or Humanity:

Image from Wikimedia Commons.
Image from Wikimedia Commons.

If you are of an apocalyptic bent and 2.8 billion years seems like too long to wait, don’t despair! It really could happen any day now – visit one of the internet’s best websites, Exit Mundi, to read all the different dire scenarios in which our species bows out, or blows out, or fizzles out, or whatever. The site kindly organizes the scenarios either by time (any day now, near future, or distant future) or by category (space, earth, science, religion).
Be warned: Exit Mundi is a huge time-sink, and we may not have all that long left.

One Equals Many: A New Take on Evolution

Looks someone needs some new microbes...
Looks someone needs some new microbes...
On the left is an example of a healthy coral, on the right an example of bleaching. Photo courtesy NOAA.

By: Sara Knight
BU News Service

When English poet John Donne claimed that “no man is an island,” he probably did not anticipate how closely his philosophical musings would align with biological theory four centuries later. As genetic research progresses, scientists are realizing that evolution may be more about cooperation among organisms than competition – truly, no organism is an island unto itself.

Biologists increasingly can pinpoint instances of interdependence among species in all kingdoms of life – leading some to believe it is time for traditional Darwinian theory to evolve. Mounting evidence of cooperation among diverse creatures and their respective microbial communities provides tantalizing hints of a more comprehensive view of life – one that challenges the definition of an organism. For decades many microbiologists have believed that no organism evolves alone, but rather as a joint effort with the millions of microscopic creatures teeming with them – fungal, bacterial, and protist. Now, evolutionary biologists are catching on: some think that natural selection acts on “super organisms,” the creature plus its microbes, rather than an organism itself.

Charles Darwin proposed the theory of natural selection in 1859, and it remains a hallmark of evolutionary biology today. Natural selection’s basic tenet is that traits that prove beneficial to an organism will become more common over successive generations. While this basic premise seems almost obvious in its simplicity, many evolutionary puzzles are left unaddressed. For example, the level of organization on which natural selection acts remained an enigma. Do evolutionary pressures act on cells themselves, or whole organisms… or even groups of organisms?

Biologists Eugene Rosenberg and Ilana Zilber-Rosenberg think they have the answer. In 2007 they proposed that organisms adapt to their environments with and because of their microbial communities. They noted that a change in the makeup of species in Mediterranean corals’ microbe population, prompted by changing sea temperatures, enabled the coral to fight off a devastating bleaching virus. The coral, which lacks an adaptive immune system, overcame a viral threat in one generation. The microbial community of the coral successfully fought off the lethal threat, ensuring its survival into another generation. Their observation led the team to develop the hypothesis that natural selection acts not just on one set of genes, but on all of the genes within (and on) an individual, including those of the micro-occupants.

Painting detail from Georges Seurat’s “La Parade de Cirque.”
Are we more than the sum of our parts?

All lifeforms possess robust microbial communities that are linked to physiologic function – humans, for example, rely on hundreds of species within our gut to digest our food and absorb nutrients. Hyenas have unique microbe collections in their anal glands, the distinctive scent of which acts as a badge of pack membership. The mixture of intestinal microbes in the common fruit fly influences with whom they choose to mate. Rosenberg believes these facts justify extending his team’s hypothesis to encompass all life, rather than just this specific Mediterranean coral.

Biologists have long accepted the importance of microbes to the lives of larger creatures – for example, the mitochondria in your own cells originated from a once free-living bacterium that was engulfed by a larger cell – yet many hesitate to agree with Rosenberg’s broad generalization of cooperative evolution in larger creatures.

Roberto Iglesias Prieto of the National Autonomous University of Mexico does not believe Rosenberg and his team proved that the Mediterranean coral was suffering from the viral perpetrator they identified. He, among other marine biologists, calls for a more rigorous examination of Rosenberg’s claim. Iglesias Prieto also cautions that an organism’s fitness might not rely on its entire set of microorganisms, but probably only its beneficial microbes.

Other biologists like John R. Finnerty, director of Boston University’s marine program echo this caveat. Finnerty does not question Rosenberg’s basic claim, but suggests the primary coral research does not support the larger hypothesis that natural selection acts on super-organisms. In some cases, a creature may need a very specific species of microbe to fill a role, while in others the co-occupancy is more of an incidental arrangement between the microbe and host, Finnerty says. The relationship between host and microbe can be very flexible – a fact that Rosenberg’s hypothesis does not address.

Despite these concerns, biologists are becoming more interested in the role our resident microbes fill. In 1998 microbiologist Lynn Margulis wrote that “the full impact of the symbiotic view of evolution has yet to be felt.” Her foresight anticipated Rosenberg’s ambitious, broadened concept of how to define an organism and a concept of evolution that stresses cooperation, rather than competition, as the main catalyst for change. Researchers are currently working toward teasing out the exact roles microbes play in the production of life, but there is a general-consensus that we literally are more than the sum of our parts.

The Unspeakable Horror of Mercury’s South Pole, or Astronomy for Lovecraftians

The unknowable!
Photo courtesy of NASA/Johns Hopkins University Applied Physics Laboratory

By Sara Knight
BU News Service

This past year NASA sent a spacecraft about the size of a standard office desk (4.5’ x 6’ x 4’) equipped with eight observational instruments into Mercury’s orbit. The spacecraft, dubbed MESSENGER, was tasked with reporting back information about that rocky little planet’s geology, magnetosphere, polar deposits, and exosphere.

The MESSENGER team succeeded – it found evidence of past massive volcanic activity, measured Mercury’s core for the first time (it takes up 85% of the planet’s radius), and even found indications that Mercury’s core may be partially liquid.

This is all good news for astronomers and the occasional Mercury aficionado (they must be out there) but why would a Lovecraftian care? Well, the MESSENGER mission also led to the team naming nine previously unglimpsed craters on Mercury’s South Pole. And as directed by the International Astronomical Union’s naming conventions, the craters’ titles honored deceased artists, musicians, painters, and authors.

Image from Wikimedia Commons
American horror author H. P. Lovecraft.

Rachel Klima, a planetary geologist on the MESSENGER team and a woman of impeccable literary taste, was particularly inspired by one of these craters, which due to its depth and position is cast eternally in shadow – creating a deep, frigid hole of unknowable features. She christened the crater “Lovecraft,” after H. P. Lovecraft, literary father of modern horror and namer of incomprehensible eldritch and celestial terrors.

Ok, so we didn’t actually find any unspeakable, unutterable terrors lurking on Mercury’s South Pole. But, who is to say if MESSENGER had audio capabilities it would not pick up on any “maddening beating of vile drums” or “thin, monotonous whine of accursed flutes” coming from with the shrouded depths of the Lovecraft crater? Or perhaps we may have even found the site where “boundless daemon-sultan Azathoth” who “gnaws hungrily in inconceivable, unlighted chambers beyond time” sits upon his black throne, the sight of which would most certainly drive us insane.

For now all we can see in the Lovecraft crater is darkness. But who can say what is looking back?

Halloween Costumes for the Scientifically Minded

By Sara Knight
BU News Service

1. The Pegomastax Africanus (“thick jaw of Africa”), or the Vampire-Porcupine-Chicken-Dinosaur

Photo from Wikimedia Commons.
Photo from Wikimedia Commons.

This is an ideal costume for the archaeology aficionado. Based off paleontologist Paul Sereno’s serendipitous rediscovery of this little cat-sized terror’s fossils in a Harvard basement last year, your costume should encompass the main features of the cute little dinosaur:

– Parrot-like beak
– Giant fangs (its 3-inch skull boasted ½-inch long fangs)
– Coat of porcupine-like bristles (you can use straws cut to a point – bonus points if you can figure out a way to get them to stand-up as a reaction to threats)

Photo from Wikimedia Commons.
Photo from Wikimedia Commons.

The creature, which skittered about the Lesotho region of Africa 200 million years ago, was bi-pedal and had grasping hands; to recreate the posture I recommend the standard “raptor” stance – arms tucked in, back hunched, head tilted.

2.Genetically-modified Mosquito with Scientist, a costume for couples

Photo from Wikimedia Commons.
Photo from Wikimedia Commons.

If you come with a built-in Halloween partner like a significant other or friendly roommate, you may want to look into couple’s costumes. One possibility is to nod to the increasingly trendy method of stamping out tropical disease – that of releasing genetically modified mosquitoes into the wild. The flies are engineered by British biotech company Oxitec.

The male mosquitoes (which do not bite – you can blame all your itchy aggravations on the ladies) are engineered with a tragic flaw. They pass down an altered version of the tTA gene to their offspring that effectively prevents the larva from developing into full-grown adult mosquitoes, thereby diminishing the population density of these insidious vectors for dengue fever and malaria.

To pull off this costume, one party needs the standard “scientist” accessories – a lab coat, beaker, glasses – while the other needs a good fly costume complete with wings, bubble eyes, and probiscus. Bonus points if you incorporate some indicator of genetic modification – maybe a big red “NO” cross on your crotch?

3. The Steampunk Insect, or the Issus Bug

Photo from Wikimedia Commons.
Photo from Wikimedia Commons.

This little guy, scientific name Issus coleoptratus, was big news in September when a paper published in Science demonstrated it as the first example of a functional gear found in nature.

The nymph form of this plant-hopper insect has two interlocking gears at the top of their hind legs that serve as propulsion mechanisms, assisting the bug in its extreme jumping acrobatics. The adolescent Issus can reach jumping speeds of 8 mph and an acceleration rate of 400 g’s – a typical human can only tolerate up to 5 g’s.

Scanning electron micrograph image of gears. Photo courtesy of Malcolm Burrows.
Scanning electron micrograph image of gears. Photo courtesy of Malcolm Burrows.

To get this look, wear your best bug costume and attach cardboard gears to your hips.

4. The Higgs Boson, or the Hardest Halloween Costume EVER:

Scientists Peter Higgs and Francois Englert won the Nobel Prize for physics this week for their work developing the concept of the Higgs boson particle, which theoretically is responsible for providing all the matter in the Universe with mass.

The closest we can probably come to representing the Higgs boson in a Halloween costume would be to recreate the read-out from a simulated collision between two protons (picture below) touted as possible evidence of its existence:

Photo from Wikimedia Commons.
Photo from Wikimedia Commons.

To get this effect, attach LED light strands to a black turtleneck. Be ready to have to explain yourself constantly, understand esoteric physics, and most likely endure exasperated eye rolls from your fellow revelers.

Anal Paste: Twitter for Hyenas?

Photo courtesy of Flickr Creative Commons user Rohit Varma.
Photo courtesy of Flickr Creative Commons user Rohit Varma.

By: Sara Knight
BU News Service

To mark the boundaries of our yards, most people plant hedges or construct fences. Hyenas, on the other hand, use paste – an oily, waxy, yellowish substance secreted from their anal glands.

Last fall I spoke with evolutionary ecologist Kevin Theis about his fascination with hyenas and his time spent tracking their various cliques as they roamed about the Kenyan Masai Mara National Reserve. During his time there, Theis became particularly interested in the hyenas’ scent-marking behavior.

Many mammalian species take advantage of their odiferous excretions – usually glandular goop, urine, or feces – to stake a claim to their territory. This behavior is known to biologists as “scent marking.” Hyenas mark their clans’ territory by extruding their anal pouch and dragging it along the ground, leaving a pungent paste trail behind them. Theis also suspects they use paste to communicate more nuanced information like fertility or advertising social status.

To determine the true nature of paste messaging, Theis first needed to identify what paste is exactly.Through a chemical analysis of the anal paste of hyenas from four different clans, Theis found that each group had a distinct “perfume” – allowing individuals to rapidly recognize if they were in a friendly or rival clan’s territory.

He also found that the waste products of microbial communities living within the hyenas’ anal pouches are responsible for paste’s distinctive odors. Each clan’s signature scent results from the unique composition of microbial species shared among that social group, meaning hyenas rely heavily on their resident cooperative microbe species for social communication.

Theis is continuing his work from the department of microbiology and molecular genetics at Michigan State University, where he aims to “elucidate the mechanistic roles bacteria play in the scent marking systems, and thus social lives, of solitary and social hyena species.” Read his blog here.

Embalming, Abraham Lincoln, and Exploding Caskets

Lincoln's Funeral Train. Photo from Wikimedia Commons.
Lincoln’s Funeral Train. Photo from Wikimedia Commons.

By: Sara Knight
BU News Service

Frequently when researching an article I find really cool tidbits of information that don’t make it into the final draft, usually in the name of word count or for the righteous goal of avoiding tangents. So for my first BUNS Science blog post I wanted to relate some interesting historical information I came across while researching embalming for my natural burial op-ed.

When Abraham Lincoln comes up, most Americans probably think of his Gettysburg Address, the Emancipation Proclamation, stove-pipe hats, or even potential hazards of attending a theatre production. Unbeknownst to many, Lincoln also played a major role in popularizing the practice of embalming our dead.

It all began with a bang. Well, several bangs. “Exploding casket syndrome” was a macabre predicament facing train operators responsible for transporting Union cadavers from the bloody Southern battlefields back to their familial burial plots up North. In the hot summer months, the stacked caskets in the trains’ boxcars had a troubling tendency to explode from the build-up of microbial gases, a normal part of bodily decomposition.

Abraham Lincoln, along with many locomotive engineers and northern bereaved, was greatly troubled by exploding casket syndrome. He also happened to be a proponent of embalming – a practice many Americans viewed with disgust and disdain. At that time, it was decidedly un-Christian and indecently pagan to fiddle about with a corpse – even as a means of preservation.

Despite its unpopularity Lincoln advocated embalming, eventually putting the official POTUS seal of approval on the practice for all soldiers killed on Civil War battlefields.

Still, the practice probably would not have caught on as quickly if it had not been for Lincoln’s post-mortem request. He ordered his corpse embalmed and taken on a 1,654-mile railcar tour from Washington, D.C. to Springfield, IL, stopping at many towns in between to exhibit the wonders of bodily preservation. At that time, the average person could only hope to see paintings, drawings, or the odd fuzzy black-and-white photo of their Commander-in-chief, so the Lincoln body tour was quite the somber sensation.

Lincoln’s preserved remains drew thousands of mourners throughout the 180 city tour. Afterwards the practice of embalming was no longer popularly associated with paganism, but rather with the great American virtue of pragmatism and the great American man who held the Union together.

This historical research site has a detailed route of the Lincoln funeral train, map included.

Visit the 2015 Lincoln Funeral Train site for more information about a planned recreation of the trip.

Dust to Dust: Considering Natural Burial

Your view
Your view
Photo courtesy of Flickr user knfk

By: Sara Knight
BU News Service

As far as we know, everyone dies. After you die your loved ones will most likely hand you off to a very professional-looking, somber stranger. This stranger will deal with your corporal remains either by the pickle-and-primp method or by crisping you in an oven that reaches up to 2,000 degrees Fahrenheit. Should the former method be chosen, your orifices will be padded with balls of cotton and sewn shut. While the blood drains from your body, the gloved and masked stranger will systematically pump you full of noxious preservatives. After your corpse is plumped full of these carcinogenic chemicals, you will be washed with poisonous fungicides and insecticides, dabbed with rouge, and stuffed into an outfit of your loved ones’ choosing.

Your body will be put into a polished metal and wood coffin and lowered deep underground into a secure, cement vault. The grounds around your vault will be regularly clipped, watered, and sprayed with pesticides. Or, if your loved ones went the “cleansing fire” route and chose cremation they will receive an urn full of what will be called your “ashes;” in actuality it is the pulverized gravel left over from your charred bones.

Embalming, the pickling method described above, coupled with the dressing, storage, funerary services, and burial can easily cost from $10,000 to $12,000, cremation $1,500 to $4,000. Both are not only costly, but ecologically harmful. Both are also entirely unnecessary.

Traditional burial and embalming require huge amounts of energy in the form of fossil fuels and manufacture of toxic chemicals, an absurd testament to inefficiency. Embalming, though not legally required, often serves a purpose as a preservative to give far-flung family members time to travel to bid the body of their loved one farewell. However, embalming does not accomplish anything a good rest in a refrigerator could not.

Mark Harris, an environmental author and proponent of alternative burials, said that 75 percent of all caskets are made with metal. We put this highly durable box into a deep pit that is lined with concrete – a “vault.” Vaults were created to prevent cave-ins should the coffin begin to degrade. They also protected a loved one’s remains from skullduggery.

Harris puts the waste into perspective in his book Grave Matters: “A typical 10-acre swatch…contains enough coffin wood to construct 40 houses; nearly 1,000 tons of casket steel; 20,000 tons of vault concrete; and enough toxic embalming fluid to fill a backyard swimming pool.”

"Arlington Tree" courtesy of Flickr user Mark Fischer
“Arlington Tree” courtesy of Flickr user Mark Fischer

We are taking huge swathes of land and making them useless for all but social visits to carved hunks of stone. This manicured, pesticide-treated collection of somber rocks could be meadowland, forest, orchards, or even community parks; a place where mourners might go to be reminded of the cyclical nature of life.

Fortunately, those of us who are either ecologically conscious or simply wary of the grotesqueries and indignities our bodies are subject to at the hands of a funeral director can now opt for natural burial. In a natural burial, the untreated corpse is shrouded or encased in biodegradable materials (cardboard, linen, or sea grass) and shallowly buried in hopes of becoming mulch. This mulch will nourish the local flora, including any memorial seeds planted by the grieving family.

Would you rather visit your grandfather’s oak tree or a slab of stone with his name on it? And even if the figurative permanence of a gravestone appeals, natural burial does not preclude this option – you can stake your chosen memorial on the burial site. We have green alternatives to embalming, cremation, and traditional burial; it is now time to lay those old practices to rest.





Thanks for the Anxiety, Grandma: Epigenetics and Mental Illness

"The Favorite" by Georgios Iakovidis courtesy of Wikimedia Commons
“The Favorite” by Georgios Iakovidis courtesy of Wikimedia Commons

By Sara Knight
BU News Service

You eat right, you exercise, you meditate daily. You had an ideal childhood with loving parents and a healthy social life. Cigarettes and alcohol? Never! And yet despite your textbook health precautions and lack of turmoil, you find yourself diagnosed with a serious mood disorder. Why? The answer may lie with the type of childhood one of your grandparents experienced – maybe your maternal grandfather was neglected as a boy and experienced social isolation from his peers. This obviously extreme illustration may be overly simplistic, but current research hints that this story may not be all that ridiculous or fictional. In mice, researchers have found evidence of grandparents’ distress manifest in the genetic code of their grandpups.

Developing a psychiatric illness may not rely so much on the genes you inherit, but rather the accessories that accompany them. Evidence is mounting that chemical changes on genes actually contribute to certain mental illnesses, not the presence or absence of a gene itself. These alterations, called epigenetic markers, influence how lively or inertly a gene acts and result directly from environmental factors. Intriguingly the evidence that these changes are heritable is also mounting, meaning for example your grandfather’s lifestyle could affect your likelihood of suffering schizophrenia. Because the changes are simple chemical reactions they may be also reversible – a fact that excites many doctors frustrated by the trial-and-error style of most psychiatric medications.

The backbone of this research is a fusion of developmental biology and genetics called epigenetics, epi- meaning “above” in Latin. Developmental biologist Conrad Hal Waddington coined the term in the early twentieth century to describe, for example, how a blood cell is able to “know” how to function as an oxygen carrier rather than a liver cell, despite containing the same instruction manual (DNA) as the cells within the liver. ‘Epigenetics’ refers to molecular “light switches” that act on DNA, telling which genes to turn on and which to turn off.

These switches consist of different molecular markers attached to your DNA. Methylation, or the addition of a methyl group to a segment of DNA, effectively tells a gene to stop interacting or to increase its output within a cell. The changes can also tighten or loosen the coil around your DNA – the looser the coil the more likely the DNA will interact with other chemicals, causing increased expression.

Epigenetics. Image courtesy Flickr user AJ Cann

Environmental stressors, diet, and exposure to chemicals all affect the changes to your DNA that can lead to altered expression. This means that your environment leaves a physical imprint on your genes and subsequently affects how your DNA is expressed. Epigenetics silences the old nature versus nurture “debate” – our genetic material (nature) is honed by our environment (nurture); there is no actual discrepancy between the two.

Doctors have used epigenetics to examine differences between cancerous cells and their healthy counterparts, but now some epigenetics researchers are setting out to tackle the notoriously complex problems presented by mental illness. Diseases like schizophrenia, depression, and bipolar disorder possess a genetic component – they run in families but there has been no conclusive “smoking gene” to predict who will develop the conditions. Mental illness and childhood trauma correlate; leading researchers to hypothesize early stress may trigger alterations on genes important in mental illness.

Researchers found mice that were traumatized in early life had grandpups with DNA that was more heavily methylated – indicating the trauma’s physical alterations on their genes could be passed down their familial line. In 2010 Isabelle Mansuy, a neurobiologist at the University of Zurich, randomly separated mice pups from their moms for a period of 14 days immediately after their birth. After that stressful period, she raised the pups normally. Mansuy found the pups that suffered early trauma had epigenetic modifications on genes related to emotional regulation and stress response. The genes were more heavily methylated. This reflected in the behavior of the mice – they had a higher incidence of the mousey version of depression and anxiety, namely increased stress and lowered grooming and social behavior.

Most intriguingly Mansuy’s male mice seemingly passed on their early ordeal’s genetic legacy through their sperm – their pups also showed the same methylated DNA despite a lack of early trauma. Dr. Tracy L. Bale of the University of Pennsylvania has found that the genetic effects of early stress can be seen in up to three generations of mice, even if the subsequent two generations are raised without stress or separation. Bale also has isolated key developmental windows in which mice are particularly vulnerable to modification.

Were the mice born with genes “marked” for depression and anxiety, or were they simply born more sensitive to environmental stressors? The research community has not reached a consensus, but Bale found the telltale methylation in the mouse sperm, indicating it is a physical transmission. Not all researchers are convinced though, especially when humans are involved.

These molecular light switches are fused onto our DNA through simple chemical reactions, leading many researchers hopeful about potential treatment options. Medications could potentially reverse these modifications and change how a gene functions, as happens in several cancer medications currently on the market. Understanding the underlying causes of mental illness could lead to an increased ability for doctors to intervene before symptoms hit. “The implications are huge from a social public health standpoint,” says neuroscientist David Dietz of the University of Buffalo. He believes that being able to identify and treat vulnerable populations means the next generation “may not be in such a doomed state.”

Though most of the hard evidence for generational transmission has been found in mice, researchers have collected retrospective data on humans that hints the same may be true for us. Researchers Alan S. Brown and Ezra Susser, both of Columbia University, linked prenatal malnourishment to an increased incidence of schizophrenia in children conceived during the Dutch famine of 1944. Humans, however, have lengthier lifespans and less motivation to faithfully participate in multi-generational studies compared to mice, so researchers have a much harder time gathering convincing data. Most human epigenetic studies concerning mental illness are ongoing and the evidence is anecdotal.

Neuroscientists studying epigenetics are still in the first phase of discovery – techniques need refining before any grand statements can be made. Researchers like Johns Hopkins researcher Zachary Kaminsky is working towards developing cleaner research techniques by cataloguing different kinds of genetic markers that may indicate the sort of genetic changes found in mental illness.