“1 e and a 2 e and a 3 e and a 4”
“Watermelon, watermelon, apple, watermelon”
“Fast, fast, slow; Fast, fast, slow”
Throughout all styles of dance there is one quality that each and every style has in common: rhythm. Whether it be ballet, tap, jazz, or hip hop, dancers throughout the world have likely heard enough terminology used to describe rhythm and movement to write an extensive dictionary (see examples above). Regardless of what new onomatopoeia an instructor chooses to use, dancers learn and translate what needs to be done. However, this is not an ability granted exclusively to dancers and musicians.
What is rhythm?
Rhythm is defined as the ability to predictively and flexibly move in time to a perceived pulse across a broad range of tempi (Patel). Simply put, it is the ability to pick out a beat and move simultaneously with it. While this task may seem straightforward, the biological process which allows us to conform to a rhythm is incredibly complex.
Is rhythm a uniquely human trait?
Charles Darwin, the master of evolutionary theory himself, proposed that animals share rhythmic capacity across species. He believed that our ability to link perception and action could be matched by other species. The neural resonance theory follows this line of thought, suggesting that our ability to perceive a beat comes from the synchronization of nonlinear oscillations in our neural pathways to outside metric stimuli. Put simply, the electrical activity within our brain intrinsically syncs up with the rhythm found in any particular audio. While this explanation may appear relatively simple, the reality is more complicated, like most scientific concepts related to the brain. After all, not all humans are capable of matching their motor functions to a rhythm, so how can this generalization be made across species? Individual skill aside, humans are able to react to all kinds of information by converting sensory inputs to electrochemical signals that our nervous system can comprehend. The way in which we process music, an auditory input, can be broken down into its rhythm, or beats, as well as other components.
So far, beat-processing is a uniquely human trait, relying on three factors: prediction, tempo flexibility, and cross-modality. A closer examination of nonhumans confirms that beat synchronization is not inherent for all species. An experiment conducted with rhesus monkeys tested their ability to synchronize to a metronome, a relatively straightforward task for adult humans (Zarco, 2009). The study revealed that the monkeys needed a year of training in order to consistently synchronize to a metronome. Even then, the gap in reaction to the beat and physical movement suggested that the tapping was merely reactive, not predictive. Observations of other animals, such as fireflies suggests that tempo flexibility is another unequally distributed ability. Even though fireflies are able to predict when to emit light alongside other fireflies through central nervous system processes (Buck, 1968), they are limited to a specific range of tempos (Hanson, 1971). The last feature of rhythmic synchronization, cross-modality, is also not replicated across species. For instance, fireflies can only display rhythmic synchronization through periodic flashing, whereas humans can snap, clap, and bob their head.
Where does musical ability originate?
It is established that humans have a unique beat-processing system. However, the heritability of this system is more nuanced than prediction, tempo flexibility, and cross-modality. A proper examination of human beat-processing requires a deep-dive into behavioral and molecular genetics, environmental features, neurological processes, and more.
Studies utilizing musical aptitude tests showing that musical traits can be inherited. A study of 15 Finnish families, 223 family members, compared musical phenotypes of family members using tests like the Karma Music Test (KMT), alongside others. The KMT is a test designed to mitigate environmental influence on musical ability, requiring the participants to detect changes in the order or number of tones in random sound patterns (Pulli, 2008). After analyzing the one hour group tests, the researchers found that musical training was not necessary for a high score on the test. For example, those who had received some type of musical training scored the same as some subjects who had never received any training. From there, the researchers obtained the DNA samples of participants over the age of 12. After genotyping the data, or examining the differences in the genotypes of the individuals, the researchers found that all of the phenotypes examined that were associated with the KMT showed heritability at 42%.
Additional research verified the heritability of traits such as duration and rhythm discrimination, isochronous sensorimotor production (simultaneous rhythmic perception and movement), and off-beat detection (Niarchou, 2022). This study conducted a genome-wide association study of the genomes of 606,825 people to find a conclusive explanation for the heritability of rhythmic ability. The study found 69 loci, general markers for genes found on a chromosome, which could be connected with beat synchronization. The locus most associated with this ability (rs848293) houses the gene VRK2, which relates to depression, development delay, and other psychiatric phenotypes. The gene also indicated a connection between beat synchronization and development of fetal and adult brain tissue. Among the loci related to beat synchronization, the traits related to beat synchronization are associated to two particular loci: in the locus rs1464791, a gene (GBE1) was found relating to neuromuscular disease and contributing to our reaction times. These loci were found in Human Accelerated Regions (HARs)—the segments of our genome separating humans from other evolved vertebrates. This supports the theory that humans’ unique musical abilities came about from an evolutionary process due to music-making’s enhancement of social and familial bonding. The research into the heritability of beat synchronization also yielded a connection between the ability itself and brain development. Simply put, multiple genes not only influence our ability to synchronize, but also relate to the development of crucial neural and motor processes.
What about other musical abilities?
When I think about true musical ability, the first artist that comes to mind is Michael Jackson. Part of what enhances his skills is his perfect pitch: the innate ability to identify and reproduce pitch. Other artists with this ability, such as Mariah Carey, Jungkook, and Beethoven, stand out from others with their natural talent (cue whistle note). However, is it a natural ability or the product of extra music lessons from a young age?
Using research techniques such as family aggregation and segregation analyses, researchers uncovered answers about the heritability of perfect pitch, formally referred to as absolute pitch (Ting Tan, 2014). Through a family aggregation analysis, researchers examined participants with perfect pitch, as well as their siblings, in order to determine if perfect pitch is clustered in families. After multiple studies testing separate families, they found that the siblings of individuals possessing perfect pitch were 20, 12.2, and 8.3 times more likely to have the trait, when compared to siblings of the control group who lacked the extraordinary trait (Gregersen, 1996). However, this study did not discriminate between genetic and environmental influence; it did not account for any early musical training consistent throughout the family. As a result, a segregation analysis allowed researchers to differentiate between genetic and environmental contribution to perfect pitch (Baharloo, 2000). Specifically, the study only looked into participants who had received musical training in their youth alongside their siblings. It found that the likelihood of siblings possessing the trait was roughly 7.5 times more. Despite the variation in results, the chance of siblings of participants possessing perfect pitch is consistently higher than those without. Studies of this trait in pairs of identical (monozygotic) and fraternal (zygotic) twins found that 11 out of 14 (78.6%) identical twins shared the most accurate form of perfect pitch, AP-1, while only 14 out of 31 (47.5%) shared the same ability.
What does this mean for me?
No singular gene marks the ability to keep a rhythm. However, researchers have demonstrated that humans possess unique musicality. Some suggest that this musicality evolved as a way to increase communication, social behavior, and encourage community. When considering the prevalence of music in both modern culture and past history, theories regarding inheritance of music ability make sense.
As for the relevance of rhythm outside of culture, not only is beat synchronization related to our cognitive and motor function, but it is predictive of language and comprehension skills, and thus speech disorders, opening up the discussion for rhythm-based therapies. All in all, not only do musical perception skills have significance ranging from our ability to dance to forming social connections, but they also have the potential to be a source for new research surrounding cognitive function and therapies for neuromuscular disease. So the next time you are watching a group of dancers follow complex rhythms, you know that the basic premise for their skill can be attributed to a heritable quality, which even you may possess.
References
https://journals.physiology.org/doi/full/10.1152/jn.00066.2009
https://www.science.org/doi/abs/10.1126/science.159.3821.1319
https://www.science.org/doi/10.1126/science.174.4005.161
https://jmg.bmj.com/content/45/7/451
https://www.nature.com/articles/s41562-022-01359-x
https://www.frontiersin.org/articles/10.3389/fpsyg.2014.00658/full
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1376907/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1287535/
https://unsplash.com/photos/person-playing-guitar-2UuhMZEChdc