Genetics is like a musical score

Amadeus Mozart and Ludwig van Beethoven may be the most genetically studied musicians of all time. Why is that? Because their music is famous and loved? Because their personal history is full of celebrity and drama? Or are they just favorites of geneticists?

The narrative in most of the published studies is to understand the interaction between musical sounds and humans. I'm still not sure if this can be completely solved because music is more than just sound. It is a musical 'language', with or without words, that interacts with with the human mind and body. However, because we are a curious species, we seek to learn about those connections. And, as I suspect, the two famous composers have had a growing foundation of research on which to build upon. 

A recent study* explores if genetic factors can determine extraordinary musical achievements. If that is so, then how do genes contribute or determine a person's musicality? This isn't a new query; geneticists have examined similar questions by studying the two famous composers for decades. However, recent advancements in molecular genetics allow scientists to probe deeper into human DNA, sometimes restudying old questions or asking new ones, especially of long-dead people.

Then again, when studying humans, sometimes these newer studies only confirm older results. 

“An analysis of the famous composer's genetic make-up has revealed that DNA data has so far been too imprecise in capturing a person's abilities.” 

In this recent study, an international team of researchers analyzed Beethoven’s DNA to investigate if and how any differences in his genes may account for his celebrated musical exceptionalism. 

The deeper question is, how much can genes impact human traits, especially behavior? When considering a bird or a lizard, probably quite a bit. But humans are “messy.” There is no single quantitative or qualitative line that divides genetically determined and learned human behavior. This is the age-old “nature versus nurture” dilemma. The lines are fuzzy.

Ludwig van Beethoven was born in Bonn (a major city in Germany), which was at that time the capital of the Electorate of Cologne and partly dominated by Roman archbishops. He moved to Vienna (1792), Austria, to flee a dysfunctional family and meet other musicians. 

During this time in history Napoleon restructured France (1789) and regions north including Bonn (1794) and Vienna (1805) after the famous French revolution. Beethoven supported Napoleon's reformations and composed his famous third symphony naming it “Napoleon”.  After Napoleon proclaimed himself Emperor (1804) Beethoven rescinded the Napoleon dedication and renamed it “Eroica”. He even refused to play this symphony in front of French soldiers.

Beethoven lived during a tumultuous era of wars and conflicts with rulers. It was the rise of the German Enlightenment period, transition from the Classical to Romantic era in art and music, almost constant family turmoil, and loss of hearing. He was a man full of emotion, conviction, and righteousness. As his music conveys, he was a man with passion. Are there genes for that?

The researchers analyzed DNA sequences available from an earlier study (2023) in which the composer’s DNA was extracted from strands of Beethoven's hair. The authors then developed a ‘polygenic score’, a number that summarizes the estimated effect of many genetic variants on an individual's trait or behavior. 

"Our aim was to use this polygenic score as an example of the challenges of making genetic predictions for an individual that lived over 200 years ago.”

They chose a specific component of music that had a score for “beat synchronization ability”, which is closely related to musicality. Beat perception and synchronization in humans is the degree to which an individual can synchronize their movements in time with a musical beat. In humans, it is commonly within 120 to 140 beats/minute and is frequently used in music composition. Ironically, beat synchronization was thought to be uncommon in non-human species and the mechanism determining the optimal tempo are unclear.

Although this was thought to be a human rhythm trait, a study in rats (2022) revealed that rats also showed head movements and neural recordings within the same range as humans. This suggests that "the optimal tempo for beat synchronization is determined by the time constant of neural dynamics conserved across species".

And Beethoven?

"The study found that Beethoven had an unremarkable polygenic score for general musicality compared to population samples from the Karolinska Institute, Sweden, and Vanderbilt University, USA. However, considering the limitations of the current polygenic scores and the fact that a genetic indicator for ‘beat synchronization ability’ may not directly tap into Beethoven’s composer skills (musical creativity), this finding is not unexpected.”

The genetic architecture of this trait is highly polygenic, meaning that it is influenced by many genes in the human genome. Authors identified 69 separate locations on the genome in which different genetic alleles (every person has two copies of a gene; they are called 'alleles') in the population account for some of the variability in how accurately people synchronize to a musical beat. 

Genes associated with beat synchronization are more likely to be genes involved in central nervous system function, including genes expressed in brain tissue and genes involved in early brain development. Recent studies also found that beat synchronization shares some of its genetic architecture with other traits, including several that are involved in biological rhythms (walking, breathing, and circadian rhythm). 

The polygenic score computes the sum of genetic effects associated with beat synchronization in each individual, but they are only a rough guess. It can tell us only what an individual’s likelihood of specific levels of beat synchronization would be in relation to the population-based model, but they do not correspond directly to an exact match with the person’s beat synchronization accuracy. Thus a person's beat synchronization may be a point amongst many in a wide area under the curve. And Beethoven's score may be lower than expected, but did that negatively impact his compositions?

“Although Beethoven had a rather low genetic predisposition for beat synchronization highlights the limitations of polygenic score predictions at the individual level. While polygenic score prediction is expected to get more accurate in the future, it is important to remember that complex human traits, including musical skills, are not determined solely by genes or the environment but rather shaped by their complex interplay.”

In conclusion the authors stated that the current study "only shows that we’ve been able to use genetics to explain a portion of the variability in beat synchronization skills (again, at the level of pooled data in a large study sample)."

When scientists talk about “heritability” they are referring to the amount of phenotypic variance explained by genetic variation. This does not mean that rhythm is only “genetic” versus only “environmental,” or that rhythm is genetic in certain people but not others.

"Scientifically we really can’t say for sure how and why an individual reaches (or does not reach) a certain level of musicality. So it’s not “either-or” but “both-and” genes and environment, and the incredibly complex biological interrelationships that occur during human development of musicality will take many, many more years of work to unravel!"

Studies of beat synchronization in humans and other species, such as in rats, found interesting genetic correlations between beat synchronization and a cluster of interrelated traits: walking pace, musculoskeletal strength, breathing function, and cognitive processing speed. Possibly even cadence in language! Additionally, the shared genetic architecture has implications for physical and cognitive function in neurodiverse people and during aging.

* "Was Beethoven unmusical?", Max-Planck-Gesellschaft Research News, published on website April 10, 2024 and accessed 20/08/2024.

Pangea gone wild

Pangea and the diversity of life. 

Most everyone knows what Pangea was: the largest supercontinent in Earth's history. All land masses united in a large group gathered together for a conference. They also shared all organisms on their surfaces before splitting into individual continents. 

This split didn't magically happen like many people think. It was a very long process. Pangea split into unequal halves forming two supercontinents: Laurasia and Gondwana. Additionally, these two landmasses continued sharing some flora and fauna over a long period of time.

Over millions of years further tectonic activity caused Laurasia and Gonwana to split into smaller landmasses gradually forming the continents we are familiar with today. This long process was a key impact on early evolution of both flora and fauna. 

The expanding distance between continents reduced exchanges of flora and fauna, eventually isolating many groups of life. Some fauna continued dispersal from continent to continent by rafts of islands or ice. Others migrated by air (e.g.seed and flying animals). Our knowledge of the degree of and when continental shifting impacted evolution of flora and fauna is continually evolving (pun intended) in the field of biogeography. There are two theories:

"Do new species come from animals populating new territory (called dispersal), or did populations get separated during Earth’s breakup (called vicariance)?"

We know that both dispersal and vicariance played roles in early evolution of nearly all flora and fauna. And we need to consider that distribution of life occurred over a long periods of time, even during different stages in the evolution of flora and fauna. Local, regional and continental changes in topography or climate can influence dispersal of isolated populations. It can also expand habitats for others enabling mixing of populations where isolation barriers once existed. 

Several approaches can help elucidate the contribution of vicariance or dispersal at different points of an organism's evolution. The most valuable is phylogenic trees, structural diagrams that represent evolutionary relationships among organisms. The pattern of branching in these trees reflects how groups and individuals of  organisms evolved from a series of common ancestors and their predicted evolutionary timing. They are evolutionary 'trees'. 

A group of scientists used the data within a set called the Timetree of Life. It is a phylogenic tree of life scaled to time. Using data for major freshwater and terrestrial vertebrate groups (animals with backbones: fish, amphibians, reptiles, birds and mammals) that were descended from common ancestors and represented on at least two continents, they examined when they diverged. 

Dates of divergence of those groups separated by continents lined up with the continents geographically separating. This supports the theory of vicariance over dispersal as the major cause for speciation. However, this may change as the data sets change. 

There are considerations that may impact this theory. One is the contribution of moving pieces of land, such as land bridges. Another is narrow bodies of water separating the shifting continents and facilitating both flora and land dispersal. 

As the author of the article highlighting the study commented, "this paper is swinging the pendulum between two competing ideas". And, as science is sometimes fraught with binary thinking, the two theories don't have to be a "competition", or mutually exclusive. Life isn't A or B; it is a dynamic collection of events that can happen together or seamlessly flow from one to the other. Generalizations don't always pan(gea) out. 

History of obesity. In Denmark.

“The origins of the obesity epidemic may be further back than we thought”

A recently published paper concluded that the rise of obesity began earlier than conventionally assumed. (See article summarizing study: The Origins of Obesity in Science.)

"This study revealed that continuous steady increases since the interwar period in the upper percentiles of the BMI distribution preceded the obesity epidemic, with an almost similar pattern in the children and the young men." (published paper)

I agree with some of the criticisms of the study and conclusions, such as population sample=1 (Denmark). Is this trend replicated in other countries? 

Another comment from a biostatistician that “slow and steady increases in obesity don’t necessarily indicate an earlier onset of the epidemic [of obesity]”. A proper data pool for that would require data before 1930’s. 

A statement from the original published paper confirms my observation over the years traveling this country: “The acceleration of the obesity epidemic has been stronger in rural and provincial areas than in densely populated urban areas, which was seen already in the beginning of the rise of prevalence in obesity in Danish young men during the 1960s.”

And, like anything involving human behavior, the contributions are multifactorial.

The high prevalence of obesity in people of all ages in rural Ohio was a shock when I moved there in late 2001. 

During a conversation on this subject with a man (late 20’s) that I was training, he commented that as agriculture became industrialized it required less physical activity by all family members. However, the culture of food and eating amongst farm families remained the same: calorically dense food, especially fats, and large portions during meals. 

Consequently, while activity levels decreased, the energy balance became very skewed towards a positive high caloric net balance. Which, over time, results in increased body mass.  

We can see an eventual similar trend in urban areas over time, albeit slower. My hypothesis is that most rural families used to grow their own food, meat and vegetables/grains. So they had an almost guaranteed supply of food and energy. 

Urban people had to purchase all their food (and still do). Purchasing power for food was based on their incomes and other debts (rent, etc). History worldwide has shown that wealthy people always have had almost unrestricted access to food. For many centuries, being overweight was a social sign of being affluent. 

It was only during the last half century when increasingly more people began moving from rural to urban communities. Industrial agriculture and food processing caused a large shift in the nutritional content and availability of food, and the culture of food. 

As Gary said that day, “People of Ohio still love their corn and pork, and there is plenty of it here. But now everyone has desk and ‘standing still’ jobs. And the kids don’t play as much; they’re glued to their phones and video games.”

The dog genes tell stories

A fantastic genome study of 2000 canids tells a 'story' of selective dog breeding over time and space. 

"Incorporating 20 × data from 1987 individuals, including 1611 dogs (321 breeds), 309 village dogs, 63 wolves, and four coyotes, we identify genomic variation across the canid family, setting the stage for detailed studies of domestication, behavior, morphology, disease susceptibility, and genome architecture and function." (Also included revisions of pre-existing data from the earlier Boxer and German Shepard genome sets)

A highlight of this is a  "worldwide sampling of village dogs and niche populations, both of which fall outside the umbrella of pure or mixed breed dogs". I'm wondering if the Viking Dogs of Dublin project might have enough genome data of discovered remains to compare with this dataset. It would be fascinating to compare this snapshot from the Midieval dogs. 

The wolf data came from 57 wolves from differing geographical areas. I'm a bit disappointed in the limited (4) coyote individuals. Especially given the admixture events in coyotes with dogs and wolves. 

"Analysis of mitochondrial data reveals surprisingly few haplotypes in dogs, with greater observed variation in wild canids." What this means is a limited pool of wild canids from which our modern breeds were first selected for domestication. 

The analyses included many comparisons: "The major clades [primary groups] are made up of breeds sharing occupation, morphological traits, and/or geographic origin. Within the larger clades, additional structure can be found with subclades (97% average cluster confidence) displaying a second layer of similarity. In some cases, clade structure reflects the relationships among breed varieties."

It revealed many surprises. e.g. in a closely related group, the Am Eskimo dog and Japanese Spitz were created from the German Spitz. 

What this analysis does is reveal the history of breeding (mostly via human selection), and results, by crossing within and between clades.  e.g. breeds within the terrier clades (breeds sharing terrier traits) as well as between the terriers and the Mastiff clades. 

"For instance, there is a long-standing history of terrier and mastiff-type breeds being crossed in the mid-1800s to form multiple bull terrier- and terrier-like breeds such as the Staffordshire Bull Terrier and the Boston Terrier. There is also excessive sharing between the Mastiff clade and the Retriever clade that has not been observed in previous phylogenies, but suggests recent admixture between these breeds or their ancestors. German Shepherd Dogs and related breeds show the largest number of admixture events with independent breeds from multiple clades. German Shepherd Dogs, specifically, have sharing values greater than 95% of background levels with 29 breeds from 13 clades and three of the non-clade breeds. !!Breeds within the German Shepherd clade are the only ones showing significant levels of haplotype sharing with wolves.!!"

All dog breeds involve some level of inbreeding (at individual and population level). That level can be estimated by comparing sets of DNA variants of gene alleles (the two versions of a gene on the same chromosome) that tend to be inherited together (haplotypes).  When two alleles are identical, they are said to be homozygous. When different, they are heterozygous. Runs of homozygosity (ROH) in an individual genome results from the inheritance of two copies of an ancestral haplotype in that individual. Thus they are homozygous by descent.  

The measure of individual or population level inbreeding is the estimated proportion of a genome that is in ROH.  "For all dog breeds, selection has involved some level of inbreeding and this has resulted in a wide range in ROH across breeds." The analyses maps proportions of historical levels of inbreeding of breed groups, breeds and sub-breeds within the groups, and compares them to feral/wild canids, including wolf and coyote. 

As you can surmise, selective inbreeding results in high levels of ROH (because humans select for specific behavioral or physical traits and interbreed to retain them). The wolf, coyote, and wild/feral canids, have the lowest level of inbreeding (coyote has the lowest of all, but based on only two individuals). 

The study also included analysis of size and breed diversity, as well as structural gene variation. The latter "plays a variety of roles in genome evolution, adaptation, and gene expression." It also searched for signatures of selection among major breed groups. 

Of major importance is the analysis of mitochondrial genomes. Keep in mind that mitochondrial genome is inherited only from the female line throughout historical descent. "Across the 1933 individuals, only 887 unique mitochondrial sequences (haplotypes) were observed. The most common was present in 52 individuals, and the 12 most common haplotypes were observed in 20% of samples (393/1933 individuals)." What this means is a limited number of female individuals form the basis of dog breeds. Would be interesting to know how many of those sets are completely or mostly associated with wolf source.

Analyses extended to causal homozygous (two copies of an allele on a chromosome) genotypes for autosomal recessive diseases, risk factors, or traits and their associated genes. As we  know, long lines of inbreeding often lead to increased recessive diseases and traits. Interestingly, this information has also been compared to diseases in humans for a few decades, providing insight to diseases in both human and canine.

A conclusion many of us already knew: "German Shepherd Dogs and related breeds show the highest allele sharing with independent breeds from multiple clades." 

 Compassionate Eye Foundation / David Leahy Getty Images 

Muscles don't have memories!!

Peeve: When the scientific community can't agree on a definition consensus for a term, such as 'muscle memory'. 

Muscles don't have memories. Brains do. 

Ask anyone in a gym and you'll get four or more interpretations of what 'muscle memory' is or means. Ask scientists and you'll get one of three; each thinking they offer the only correct definition. 

This was a frequent source of amusement in our lab (neuromuscular pathology); we agreed to avoid the term unless being sarcastic. We often used the general term 'muscle plasticity': the ability of a given muscle to alter its structural and functional properties in accordance with the environmental conditions imposed. That's what muscles do. 

Then, what IS muscle memory?

According to Wikipedia (and a more summarized definition in Oxford Dictionary), 'muscle memory' is:

"...a form of procedural memory that involves consolidating a specific motor task into memory through repetition, which has been used synonymously with motor learning. When a movement is repeated over time, the brain creates a long-term muscle memory for that task, eventually allowing it to be performed with little to no conscious effort. This process decreases the need for attention and creates maximum efficiency within the motor and memory systems."

So, what is muscle plasticity? 

Phenotypic* plasticity allows single genotypes to express different phenotypes under diverse environmental conditions. Organisms, and tissues (some more than others), respond to different environments by changing how they act, look or function. Skeletal muscle is a highly plastic tissue. 

For example, exercise initiates signaling pathways that modify muscle fiber metabolic, physiological and contractile properties of skeletal muscle (sometimes referred to as 'remodeling'). That is 'muscle plasticity'. Whereas exercise can also evoke memories (conscious and subconscious) in the brain of how movements are executed. It is a back-and-forth communication between muscles and the brain via the central nervous system. That is  'muscle memory'.

In language, adjectives connote specificity. In particular, 'neuromuscular plasticity' and pathology were the focus of our research. Muscle plasticity requires the coordinated interaction between neurons and muscles, but pathology narrows the focus. Disease or injury of motor system components, including responsive proteins in muscle fibers, can lead to muscular motor dysfunction. Like all tissues, biological/molecular processes are included. 

One example is muscular dystrophy: a disease in which one or more muscle proteins are absent or dysfunctional because of genetic aberrations that interrupt the signal between the motor neurons and the ability of the muscle to respond. It has little if anything to do with procedural memories, aka 'muscle memories', in the brain. A muscle group without dystrophin won't be able to contract, irrespective of any 'muscle memory' in the brain. 

Using the correct language is imperative for science communication within the scientific community. Incorrect** and vague terms are perpetuated throughout communication and education (formal and informal) outside of that community, such as with medical professionals, trainers, social media, etc. Yet confusion remains if members of the scientific community do not consistently use correct definitions of terms. This needs fixing.

Summarily, the use of the term 'muscle memory' should be restricted to the associations of movement and 'memories' established in the brain. Better yet, these terms are better:

• Procedural memory ( or 'Kinesthetic memory'): the automatic movements involved in throwing a ball, dancing, swimming, steering a vehicle, typing, or even squats.), or
• Motor memory:  process by which animals can adopt both persistent and flexible motor behaviors. 
  
  

MUSCLES DON'T HAVE MEMORIES!
Brains do.

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* Phenotypic is the observable traits of an individual resulting from the interaction of its genes (genotype) and its environment. 

** Many researchers have recently published papers in scientific journals and still use the term 'muscle memory' in the context of muscle biology/molecular biology and physiology without ANY reference to -'memories' formed and stored in the brain! 

Being inside out

Modern biotechnology is wonderful. It reveals wonders that we can't see without it. It tells us more about ourselves and about each other, about living things that surround us. Ironically we can see inside our bodies, but still scratch our heads on the outside wondering how we tick inside our brains.

Many years ago, while spending days [1] extracting DNA from large quantities of white blood cells from cows' blood, I added a small tube of my own WBCs. There was room in the centrifuge; why not? The feeling of seeing thin threads of your own DNA floating in solution inside a gently rocking test tube is inexplicable. 

Those fine threads were a history catalog of generations before me, before my mother and father, before them. They were strings of time more ancient that any of us can fathom, carrying the instructions on what makes me human. And how similar yet different I am from each of you. Ironically, even similar to the thick ropes of cow DNA rocking alongside in their own test tubes.

Trypanosoma theirleri and red blood cells

[1] I collaborated with a colleague to develop a sensitive assay (PCR) for detection of microscopic single-celled parasites (Trypanosomes) in the blood of cows. They literally beat up blood (red and white) cells with their 'tails' (flagellum) and weaken the animal's immune system. The process entailed extracting DNA from the fraction of liters of blood containing the WBC; in that fraction were the parasites and their DNA. A close 'cousin' of the same parasite causes Sleeping Sickness in humans.

An American Mutt (revised 12.2022)

Like most Americans I'm a 'mutt': a combination of different nationalities, rather than one identifiable national identity. Maybe I'm the only one that admits it, and proud of it. Also fitting, considering my inexplicable interest, both scientifically and personally, in canids. All canids, not just dogs and wolves.

I'm a mutt through and through. So my loyalties extend to all people and almost all real canids (those tiny dogs just aren't real canids; they're genetic mistakes).

I grew up not fitting in anywhere. And not really understanding that until I spent a summer in the Middle East and Europe. Then I realized I'm simply a member of the human race. That's all I needed to know.

We're all human.

There are no sub-species for Homo sapiens. Yet we act like there are. Our species is a very tribal one. We look for anything to belong to and separate our selves from others, pledging loyalty to this and that, and resenting any group that doesn't match our criteria. Our species is in a perpetual identity crisis.

I blame it on taxonomy. Anyone in biological sciences is bottle fed systematics: the classification of every life form. Taxonomy is a scheme of classification, usually in a hierarchical approach in which living things are organized into groups or types. People classify themselves the same way.

People born in Greece are Greeks; in Mexico, Mexicans; in America, Americans. People born in the Britain are Brits. However, if I were born in Scotland, a member of Britain, I'd be both a Brit and a Scot.

I was born in the United States of America and legally, I am an American. But I really don't feel like one. At least, not compared to how many of my fellow American citizens feel 'American'. I don't share the tribal loyalty (often blind) that many do.

So what am I?

I'm what??

My last name comes from Germany and my first name is a corrupted form of the German/Scottish/English 'Elspet/Elspeth/Elizabeth'. (Even my name is a mutt.) American names aren't original; they are fragments from many countries strung together to label a person accompanied by a unique social security number. The latter is what makes us American.

Because my parents rarely talked about their family history, my sister and I researched our family genealogy after they passed on. The patriarchal tree is relatively simple: married immigrants from Bavaria arrive at Ellis Island in 1861 with their five children, settle in Buffalo, NY, and birth six more children. Most of the male offspring married Irish or Scottish women, who also had up to 12 children, and so on. Ironically, many of the female offspring are dead ends: once they marry, their adopted husband's last names render them lost in history.

I'm fourth generation American-German.

The matriarchal tree is even simpler: my maternal grandmother was born in Sweden. Her parents were born in Sweden. That was easy. That makes me second generation American-Swedish.

I did what many people are doing now: ancestry DNA. I discovered that human DNA is much more complicated than the bacterial and viral DNA I was used to be. Like any genetics project, genetic information is dependent on data derived from a population of samples. If that sample pool is small, the data is also limited and may not represent the larger population. Also, as gene sequencing technology changes, so does the size and confidence of the data. Consequently, as more genetic data from people around the world are added to central databases, the more precise the genetic information of ancestors. It also adds to the histories of human migration over thousands of years.

One genealogy autosomal DNA analysis reported that I am 68% Scottish/Irish, 19% Scandinavian, and......13% German*?? Another analysis reported 44% German, 19% British Isles, 14% Slavic**, 11% Italian, and the small balance Scandanavian (2%), French, and 2%.... Peruvian??

Oh, what the hell.....  I'm a mutt. And proud of it.

*It's more complicated than that. What DNA companies don't explain (except for CRI Genetics) is that a person's DNA does not give a crap about labels and borders. The reason many people with known German ancestry are pinned to the United Kingdom, or other modern countries, is because Germany was not a unified country with a common border until 1871. Before then, the region was occupied by many ethnic groups: Romans, Germanic tribes, Celts, and, going back to the Bronze Age, the Yamnaya (originally from the steppes of western Russia). For example: Bavaria was a 'hot spot' of migration mixing.

** Preliminary online research into Scandanavian DNA projects, the Finnish DNA Project (Finnish DNA Reference Group) shed some insight into the Slavic connections. Although mtDNA (DNA from female mitochondria) provides more exact information (especially, haplotypes), "Overall, as we know from autosomal studies, Finnish ancestry derives primarily from Europe, especially the Baltic region". Many Finns migrated and settled in Norway and Sweden. That explains the Slavic connection. 

We are all mutts.

For those interested in the seven-year 1000 Genomes Project, this link leads to a summary of the project (published 2015 in Nature journal).  Data from diverse human populations, such as the Finnish Project mentioned, continue to be added. This and other smaller genome projects (e.g. link to overview of UK genome projects) serve as a basis for genetic genealogy data sources used by commercial DNA/genealogy analyses. The current expansion of this effort can be found at The International Genome Sample Resource. 

"1000 Genomes Project publishes its final two papers, which analyze 2,504 genomes from 26 populations and provide the most comprehensive view of global human variation so far."

Is life like Play-Doh?

On the tail of the silver fox.......

Despite that the field of epigenetics is often dismissed as a fad topic, that may come back to surprise us, just as the derision of ‘junk DNA’ did several decades ago. 

Similar to the silver fox domestication project, scientists in Sweden replicated domestication of red jungle fowl (ancestors of modern chickens) and selected for fear of humans tameness. After five generations, they examined changes in the genetic structure associated with certain phenotypic traits, especially behavior.

Behavioral traits are associated with many physiological and neural mechanisms. Signaling compounds in the body involved with these processes are dopamine, glucocorticoids, epinephrine, and many others. All of these signaling molecules are synthesized in tissues and organs, such as they hypothalamus. Based on prior studies, the research team examined changes in the hypothalamus of  their test subjects. They discovered that not only were DNA methylation patterns associated with cellular metabolism and neural signaling, but there were sex-specific changes.

In agreement with other similar studies of selection pressure during domestication, this study adds further evidence that changes in genetic structure are related to the driver(s) of selection for specific traits, such as egg size in a breed of domesticated chickens.

“This suggests that different selection pressures generate distinctive sets of epigenetic changes, which in turn are related to specific phenotypic traits.”

Epigenetics may have increasing importance now because of its suggestive role in phenotypic plasticity, which often precedes adaptation to environmental change. Understanding how organisms respond to selection pressure can help us better model and predict the fates of many species of concern in this age of rapid climate and anthropogenic changes. Including our own.

“Our results suggest that bidirectional selection for tameness involves epigenetic factors that can even differ in a sex-specific manner. Observation of divergent DNA methylation patterns in the hypothalamus after only five generations of artificial selection highlights the importance of epigenetic mechanisms, in addition to genetic composition, in evolutionary phenotypic variation that emerges in response to selection pressures.”

A researcher in Europe has been studying these association based on changes in gene expression in melanin, phenotype, and behavior adaptation in owls. Ironically, humans have unknowingly been experimenting in this for thousands of years by our own selection for domestication of many plant and animal species.