What are the origins of rhythm and time signatures (2/4, 4/4, 3/4)? An explanation of their evolutionary and historical origins!

When you take up listening to music, singing, or dancing as hobbies, you naturally become interested in rhythm and time signatures.

However, if we consider its origins, there are many aspects that we cannot answer. We often find ourselves moving to rhythms so naturally that we don't even question it, but this ability is actually very limited among living organisms, and it's fair to say that the ability to predict rhythm is unique to humans.

While there's no definitive answer as to the root cause of why that rhythm feels pleasant, one theory suggests that "walking" is deeply involved, and that it's also the origin of 2/4 and 4/4 time signatures. However, the concept of time signatures based on proper music theory itself only emerged in late medieval Europe with the birth of Baroque music.

The triple meter is considered unique and became widely used in 16th-century Austrian waltzes, supposedly because it matched movements that involved rotation.

This article will explain the origins of rhythm and time signatures (2/4, 4/4, and 3/4) from an evolutionary biological and historical perspective.

What is the origin of our sense of rhythm? Humans aren't the only ones who keep the beat!?

Rhythm is defined as "a phenomenon that repeats in a certain pattern that living beings can perceive."

The act of keeping rhythm is a phenomenon that is widely observed in organisms ranging from insects to monkeys, and there are examples such as the following (Iversen, 2016).

animal species	Characteristics of Synchronization	remarks
Frogs	Synchronization of calls (chorusing).	This behavior is related to breeding. Male frogs synchronize their calls to increase the overall signal strength of the chorus, aiming for a "beacon effect" that makes the location of the calls more conspicuous.
Insects (e.g., crickets)	Synchronization of calls within a flock.	Same as above.
Parrots	Movements synchronized with the music (e.g., shaking your head).	Related to the ability to imitate speech.
Pigeons	It is possible to identify the periodicity and tempo of sounds.	The perception of beats has not been confirmed.
California sea lion	Move in time with the music tempo.	Its ability to mimic voices is unknown, but it does have the ability to synchronize with rhythms.
Macaque	Through training, the tempo can be adjusted, but the response to the beat is delayed.	Predictive synchronization of beats is difficult.
Chimpanzee	Slight synchronization occurs only when the tempo is close to the spontaneous tempo.	Beat extraction has not been confirmed.

It's still unclear whether this sense of rhythm, from insects to humans, is due to genes that were common to all of them in evolutionary biology, but it seems that a certain degree of rhythmic sense is inherited.

What is the origin of the innate human sense of rhythm and the 2/4 time signature? Was the birth of walking the most important factor?

However, humans (and some birds) are thought to have developed a special sense of rhythm called "Rich BPS (Rich Beat Perception and Synchronization)" (Iversen, 2016).

Rich BPS consists of the following elements:

Components	Content	Status of confirmation in other animals
Predictive synchronization	It moves by predicting the timing of the sound (prediction, not reaction).	Partially confirmed in some bird species.
Generation of internal beats	It's possible to maintain a beat even without sound.	Only humans were clearly identified.
Processing of hierarchical beat structures	Processing multiple tempos and time signatures simultaneously (e.g., polyrhythms).	The parrot example partially suggests this.
Active perception	The motor system influences auditory perception (ASAP hypothesis).	Not confirmed in other species.
Cultural and training-based expansion	The ability to sense a heartbeat improves with experience and learning.	Only confirmed in humans.

In short, it could be described as the ability to actively and predictively understand rhythm. It is currently believed that animals other than humans either lack this ability or possess it to a very limited extent.

So, what is considered to be the origin of Rich BPS and the 2/4 time signature?

Although there are various theories, walking is considered a very important factor (Iversen, 2016; Fitch, 2016).

For bipedal animals, the most energy-efficient form of walking is thought to be isochronic walking (walking with a constant period). Therefore, they move their left and right legs in a rhythmic manner.

It is believed that all humans, to varying degrees, instinctively acquire a sense of rhythm in order to grasp this sense of tempo.

There is a theory that the feeling of "pleasant rhythm" is an evolutionary by-product of "the motivation for infants to start walking."

Even adults sometimes feel a sense of comfort while taking a walk, which can be rephrased as finding the periodic vestibular and auditory inputs pleasant.

This theory suggests that the enjoyment of walking, stemming from periodic vestibular and auditory input, led to a preference for singing and dancing, which involve movements that stimulate the auditory and vestibular senses.

From another perspective, when bipedal animals walk in groups, if they can synchronize their walking rhythms, they may be able to quickly detect enemy groups, predators, or prey whose footsteps are not in sync. Furthermore, the size of the group can be concealed by layering sounds. This can also be considered a significant advantage of the evolution of Rich BPS .

In music theory, 2/4 time is monotonous because it consists only of strong and weak beats, and nowadays it is only used in marches, popular songs, and a few other genres, having largely given way to 4/4 time.

What is the origin of the 4/4 time signature?

4/4 time is a time signature with four beats per measure. It is similar to 2/4 time, but is generally distinguished by the fact that the strength of the beats progresses from strong to weak to medium-strong to weak. However, since the strength of the beats is not the sole definition of 4/4 time, it seems that the distinction is largely based on convention.

4/4 time, where a quarter note constitutes one beat, is the most widely used time signature in modern music and is used extensively in all genres, including rock, pop, dance music, classical, and jazz.

So, what do you think is the original origin of 4/4 time?

This is indeed considered to be walking (Fitch, 2016). However, the interpretation of walking changes slightly in this case.

When you're walking, you think of it as "sound of kicking with the right foot → sound of lifting the right foot → sound of kicking with the left foot → sound of lifting the left foot."

If we think about it this way, we get a time signature that follows the pattern of "strong beat → weak beat → strong beat → weak beat".

However, to the best of the author's knowledge, there are no papers that offer a clear explanation for the emergence of "mid-strong beats." While it's intuitively clear that the presence of "mid-strong beats" adds complexity and makes the music more enjoyable, it may remain a scientific mystery.

The "4/4 time signature" of "strong beat → weak beat → medium-strong beat → weak beat," based on modern music theory, is believed to have originated in the dance music of the early 17th century Baroque period, but its formation process is not well understood.

Even now, with the advent of DTM (Desktop Music) and the ability to reproduce any kind of music, the fact that even time signatures, along with the aforementioned 2/4 time signature, are still among the most widely used in pop music suggests that we instinctively prefer even time signatures, which resemble walking rhythms.

However, this approach alone cannot explain complex music that is not mainstream, such as music with irregular time signatures, groove, laid-back, push, offbeat, syncopation, and swing. While not mainstream, this music cannot be ignored and has achieved commercial success. While there's a strong sense that "being offbeat is more fun and comfortable," its biological origins remain a great mystery.

However, I also feel that these techniques are valuable when used in a partial manner.

What is the origin of the triple meter?

Triple time is a time signature with three beats per measure, consisting of a strong beat, a weak beat, and another weak beat. It is a time signature commonly used in Western dance music such as waltzes and minuets.

Typical time signatures include 3/4 time, where one beat is a quarter note, and 3/8 time, where two beats are eighth notes.

How did the triple meter come about?

While it may have originated even earlier, in Europe, mensural notation, which emerged in the late Middle Ages and early Renaissance, made it possible to accurately write the length of notes. It was then that, theoretically, triple time became possible.

In fact, the widespread use of triple time is believed to have originated in the waltz, at least in Europe (Fitch, 2016). There are various theories, but it is thought to have become popular in Europe around 1580 and developed from German and Austrian folk dances (Buurman, 2021). As a side note, the Japanese Wikipedia states that it was established in the 13th century, but there is no source for this, and there is no such statement in the English version.

In the Viennese waltz, a series of steps (step → turn → bring feet together) are interspersed between turns, with each "bringing feet together" action serving as a short break to prepare for the next step with the opposite foot. This creates a cycle of six steps, with both the right and left feet taking steps.

The unique aspect of this movement is that it involves rotation, and it is believed that a 3/4 time signature naturally becomes optimal when this action is involved.

Triple time can be considered a relatively new time signature, having emerged after the development of more relaxed dances.

What are some other theories about the evolution of rhythm?

There are several other theories regarding the evolution of rhythm, which I will introduce for reference (Iversen, 2016; Seki & Tachibana, 2023).

The Vocal Learning Hypothesis posits that a sense of rhythm evolved as a byproduct of the ability to imitate voices. This is supported by the fact that parrots and humans possess both the ability to imitate voices and a rich rhythmic perception (RPS ). However, this contradicts the fact that non-vocal mimicry animals (such as sea lions) also possess a sense of rhythm. This might simply be a pre-adaptation for acquiring neural circuits that convert auditory input into motor output.

The theory of sexual selection, proposed by the renowned evolutionary psychologist George Miller, suggests that musical ability was advantageous in mate selection. However, the fact that both sexes possess musical ability contradicts the typical theory of sexual selection. Nevertheless, since there are differences in musical preferences between men and women, it is possible that sexual selection occurred incidentally after the evolution of rhythmic sense.

The social bonding and group cooperation theory posits that rhythm evolved to promote group bonding and cooperative behavior. This seems natural when we consider the sense of unity we feel and the mosh pit we form at live concerts today. However, natural selection usually occurs among individuals or closely related groups, and this type of evolution falls under the category of "multilevel group selection," which is different from the usual pattern. This idea is not very popular in evolutionary biology because there is debate about its interpretation (although I think there is some truth to it). Moreover, it seems that rhythm is not the only thing that could promote bonding, so perhaps the sense of unity is a consequence of the evolution of rhythm.

The maladaptation theory (music being a byproduct) was proposed by the famous psychologist Steven Pinker, who argued that music is an "auditory cheesecake," a pleasure-seeking technique, and not an evolutionary adaptation. While it's true that modern, pleasant music might be like a cheesecake, the very sense of rhythm itself seems to be an evolutionary product.

Currently, the prevailing view seems to me that the fundamental sense of rhythm evolved in conjunction with walking, but this may change depending on future research.

References

Buurman, E. 2021. Early Viennese Waltz Dances. In: E. Buurman (Ed.), The Viennese Ballroom in the Age of Beethoven (pp. 32-54). Cambridge University Press. ISBN : 9781108797856, https://doi.org/10.1017/9781108863278.003

Fitch, WT 2016. Dance, music, meter and groove: a forgotten partnership. Frontiers in Human Neuroscience 10: 64. https://doi.org/10.3389/fnhum.2016.00064

Iversen, JR 2016. 21 In the beginning was the beat: evolutionary origins of musical rhythm in humans. In: R. Hartenberger (Ed.), The Cambridge Companion to Percussion (pp. 281-295). Cambridge University Press. ISBN : 9781107472433, https://doi.org/10.1017/ CBO 9781316145074.022

Seki, Yoshimasa & Tachibana, Ryosuke. 2023. Animal rhythm synchronization ability and its origins. Journal of the Acoustical Society of Japan 80(1): 33-40. https://doi.org/10.20697/jasj.80.1_33