Comparison of bird calls and human music: an evolutionary approach

By Julián Monge-Nájera

Centro de Investigación General, UNED, Sabanilla de M. Oca, San José, Costa Rica. (Mailing address: Biología Tropical, Universidad de Costa Rica, 2050 Costa Rica). Telefax (506) 2511-5550

"Birds have many abilities that humans assume are unique to humans, including musical ability (appreciation, composition, and performance) ... they also can communicate meaningfully with humans and relate to them as close, caring friends" Barber (1993)

The ancient Greek idea that human music began as an imitation of complex avian calls has a special appeal, perhaps because we still admire the sounds produced by these small vertebrates and popularly call them "bird songs". This attraction survived the shift from a poetic interpretation of birds as nature's musicians created to please the human ear, to the biological identification of mating and territorial functions in such sounds.

To a biologist like me, this functionality of avian calls immediately suggests that their characteristics evolve by natural selection, but to readers with a different orientation, the analysis remains valid because it is based on published data of call characteristics (see for example the anthropological interpretation by Feld, 1990).

The philosopher's idea is a hypothesis that can be tested by its predictions. An obvious prediction is that if human music is an imitation of avian calls, then it should resemble such calls. If such resemblance is lacking, the hypothesis will not be supported.
This paper is a comparison of known avian call traits and their effects on call characteristics, with apparent equivalents in human music.

The inherited call pattern of birds is coded in chromosome DNA, a nucleic acid known to suffer alterations (mutations) during its translation and storage. The result is a modified call. Mistakes made by copyists when reproducing partitures seem to be an obvious equivalent of DNA mutation. Chromosome mutations range from very small (micromutations) to translocation of large segments and loss of whole chromosomes (macromutations). For the human partiture, and even for the non-professional musician playing by memory, equivalents of micromutation, translocation and chromosome loss are, in the same order, a mistaken note, playing a compass in the wrong place, and missing a complete page of the partiture.

Not all bird calls are innate. Some are learned and there can be mistakes both by teacher and student, just as in humans. Besides errors, improvisation produces a change in calls and songs, and some readers may be surprised to learn that the phenomenon, so familiar in human music, is also known to exist in bird calls (Table 1).

My second section of call characteristics refers to sexual selection, and here I give examples in which the female, often judging a group of males ("lekking"), affects male call characteristics by mating only with the male that produces what she apparently considers a good song. The biological interpretation is that the resulting offspring will inherit call traits that this and other females like.

Males that fail to attract females are unable to pass their song codes to future generations, and thus their song patterns are lost, eliminated by sexual selection. However, I must make it clear that in some cases, it is the male that invests more to rear the young (nest construction, food foraging) and then the roles are switched, with females trying to attract the males.

The result of call sexual selection includes louder, harsher and more frequent calls, as well as other characteristics summarized in Table 1, which provides more details for all cases than I can present in the main text. Many equivalents in popular music, from rock-and-roll to some popularized opera selections are suggested in Table 1.

According to some biologists, when songs are not selected per se, but because they reflect good characteristics in the singer, sexual selection may not be the appropriate interpretation, but rather natural selection. This is believed to result in highly complex and clearly individualized calls. Examples that appear to be equivalent in human music range from Latin American folk music to musical television stars (Table 1).

Ecological factors such as population size and predation pressure shape bird call patterns and I could suggest some similarities with religious and Amerindian music (Table 1).

The final block consists of call characteristics believed to reflect mainly male-male interactions in birds. Military music may represent human equivalents (Table 1).

In the table, I have cited examples that refer to human culture at the end of the 20th century. Someone reading this work many years from now may not understand them because names that are almost universally known today, such as Iglesias or Pavaroti, may have been forgotten by then. But no doubt, that hypothetical reader will have some possibility of suggesting her or his own equivalents.

I have not included in the table all the examples I could think of, and in some cases I could not suggest human equivalents. Even so, the general impression left by data in Table 1 is that there is much similarity between avian calls and human music. With this result, one may immediately think of two basic possibilities: human music is truly the result of imitating bird calls, or both independently reflect forces that act on acoustic signals just like fishes and submarines resemble each other for hydrodynamic reasons. Finally, similarities may also reflect a common genetical origin rather than immitation (Wallin 1991).

In conclusion, the working hypothesis of a common origin cannot be rejected, but of course it is by no means proved because hypotheses can never be proved, as was so ardently stated by philosopher Karl Popper throughout his life. The evaluation must continue, and new data and tests, as well as repetition of valid tests, will refine our appreciation of that idea that illuminated a Mediterranean brain thousands of years ago.

I thank the advice, support, assistance and constructive criticism of Graham Pont (University of New South Wales) and the participants in the Music Seen by Philosophy and Science Symposium (San José, Costa Rica, 1997). Graham also provided me with much valuable literature that was impossible to obtain in Costa Rica, as well as warm friendship and enthusiasm.


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Some factors that affect the evolution of avian "songs" and their apparent equivalents in human music.
Factor Effect Source and group Musical equivalent
Micromutations  Different song ("new dialect") Sparrows and chaffinches (Haffner & Petersen 1985, Linch et al. 1989)  Copyst errors
Learning errors  Different song ("new dialect") Sparrows (Haffner & Petersen 1985) Student errors
Teaching errors   Different call ("new dialect") Sparrows (Haffner & Petersen 1985) Teacher errors
Improvisation   Different call ("new dialect") Sparrows (Haffner & Petersen 1985) Some Brazilian folk music,  Jazz, some religious songs of India
Calls learned outside family context  Kin have different calls Buntings (Payne et al. 1988) Humans families in which some teenagers are oriented to classical music while others prefer rock
Females prefer natal dialect Inbreeding Buntings (Payne et al. 1988) Nueva Trova Latinoamericana among left militant girls
Females do not prefer father's call Outbreeding Buntings (Payne et al. 1988) The 50's rock generation in comparison with their parents
Females prefer calls that reflect high mate quality  Call convergence in unrelated birds Several families (Lofredo and Borgia 1986)  Pop music fans (e.g. Enrique Yglesias, Luis Miguel)
Idem Loud calls Several families (Lofredo and Borgia 1986, Searcy & Andersson 1986) Pavaroti fans
Idem Frequent calling Several families (Lofredo and Borgia 1986) Fans of successful pop groups
Idem Harsh calls Several families (Lofredo and Borgia 1986) Fans of heavy metal and "satanic" pop groups
Idem Mating calls similar to aggressive calls Several families (Lofredo and Borgia 1986) Fans of successful pop groups
Females prefer larger males Calls with lower frequencies Many species (Searcy & Andersson 1986) Pavaroti and Neal Diamond fans
Call complexity correlated with male fitness Call rich in frequencies Many species (Searcy & Andersson 1986)  José Carreras compared with Julio Yglesias
Call indicates material resources offered by male Individual call Many species (Searcy & Andersson 1986) Latin American folk music (e.g. "Caña dulce pa moler", Costa Rica)
Call indicates capacity to fertilize eggs Individual call Many species (Searcy & Andersson 1986) None
Call reflects male attractivity (sexual selection, Fisherian selection, runaway selection) Individual call  Many species (Searcy & Andersson 1986)  Enrique Yglesias compared with Johnny Cash
Cuckoldry  Males modify calling if cuckoldry pressure is perceived Several song birds (Pape 1991)  ?*
Need for reproductive isolation Call species-specific or population-specific Many species (Searcy & Andersson 1986)  None
Population size Units (= memes = culturegens) sang by more individuals have lower extinction rate  Buntings (Payne et al. 1988) Pre-conquest Andean music in comparison with native Patagonian music
High predation pressure Shorter calling time per day Warblers (Shutter and Weatherhead 1990) Religious singing in Stalinist Europe
Idem Shorter calls Warblers (Shutter and Weatherhead 1990) ?
Idem  Simpler calls Warblers (Shutter and Weatherhead 1990) ?
Idem Smaller repertoire  Warblers (Shutter and Weatherhead 1990) ?
Habitat complexity  Singer may adapt song to accoustic characteristics of hall Change of component frequencies to reduce reverberation Oscines (Wiley 1991) ?
In male-male interactions, call indicates:
Species Species-specific call Many species (Searcy & Andersson 1986) Probably all songs
Resource holding power  Call characteristics correlated with power Many species (Searcy & Andersson 1986) Military songs (e.g. Costa Rican national anthem)
Agressivity Call characteristics correlated with agressivity Many species (Searcy & Andersson 1986) Military music (e.g. African war songs)
Local density of conspecific males  Call characteristics correlated with density Many species (Searcy & Andersson 1986) ?
Individual identity Individual call Many species (Searcy & Andersson 1986) Mexican corridos