Penguin vocal patterns follow the same principles as human linguistics, new research suggests.
The animals follow two main laws – that more frequently used words are briefer (Zipf’s law of brevity), and longer words are composed of extra but briefer syllables (Menzerath-Altmann law). Scientists say this is the first instance of these laws observed outside primates, suggesting an ecological pressure of brevity and efficiency in animal vocalisations.
Information compression is a general principle of human language: the most frequently-used language tends to be compressed, so that information can be shared quickly.
According to the study published in the Biology Letters journal, display songs of the endangered African penguin conform to two linguistic laws, known as Zipf’s law of brevity and the Menzerath-Altmann law.
The research was led by the Equipe de Neuro-Ethologie Sensorielle of the University of Lyon/Saint-Etienne. Dr Livio Favaro, of the University of Torino, and colleagues say this is the first evidence of a non-primate species following these linguistic rules.
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Researchers recorded and analysed 590 ecstatic display songs from 28 adult African penguins, belonging to three different colonies in Italian zoos, during the breeding periods in 2016 and 2017. They found the words used most often by the flightless birds were the shortest, while the longest words were made up of shorter syllables.
The study sets out: “Our results demonstrate that ecstatic display songs of the African penguin follow Zipf’s Law of Brevity and the Menzerath–Altmann Law. This is the first compelling evidence for conformity to linguistic laws in vocal sequences of a non-primate species.
“As predicted, we found that the duration of the syllables was inversely correlated with the frequency of occurrence.” That is, the longer the syllable, the less frequently it was used.
The authors add: “We suggest that relationships between element duration, frequency of use and song size are mainly a consequence of vocal production constraints interacting with selective pressures for intersexual mate choice and territorial defence in dense colonies.
“Importantly, our results suggest for the first time that information compression can coexist with other sources of selection in a non-primate species with a small and relatively fixed vocal system.”
Reader Q&A: How did languages evolve?
Asked by: Tanya Sebastian, by email
Slowly at first, possibly beginning with simple sounds made by our ancestors Homo heidelbergenis, and then increasingly rapidly until there were thousands of languages spoken around the planet. But this has been fiercely debated and much is still not understood.
Some experts think there was one original ‘Proto-Human’ language from which all others evolved. This might have been spoken by Mitochondrial Eve about 150,000 years ago, before our ancestors left Africa.
Others believe that, since some human populations have been isolated for as long as 40,000 years, language evolved independently many times.
What we do know is that languages evolve much as organisms do, with isolated populations diverging in vocabulary, words changing to suit different functions, and some languages ultimately going extinct.
Of the nearly 7,000 languages spoken on Earth today, 90 per cent are expected to be gone by the middle of this century. Sad, but that’s evolution for you.