{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,1]],"date-time":"2026-04-01T00:40:54Z","timestamp":1775004054197,"version":"3.50.1"},"reference-count":82,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2022,4,5]],"date-time":"2022-04-05T00:00:00Z","timestamp":1649116800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000286","name":"British Academy","doi-asserted-by":"publisher","award":["GP300169"],"award-info":[{"award-number":["GP300169"]}],"id":[{"id":"10.13039\/501100000286","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>Functional load (FL) quantifies the contributions by phonological contrasts to distinctions made across the lexicon. Previous research has linked particularly low values of FL to sound change. Here, we broaden the scope of enquiry into FL to its evolution at higher values also. We apply phylogenetic methods to examine the diachronic evolution of FL across 90 languages of the Pama\u2013Nyungan (PN) family of Australia. We find a high degree of phylogenetic signal in FL, indicating that FL values covary closely with genealogical structure across the family. Though phylogenetic signals have been reported for phonological structures, such as phonotactics, their detection in measures of phonological function is novel. We also find a significant, negative correlation between the FL of vowel length and of the following consonant\u2014that is, a time-depth historical trade-off dynamic, which we relate to known allophony in modern PN languages and compensatory sound changes in their past. The findings reveal a historical dynamic, similar to transphonologization, which we characterize as a flow of contrastiveness between subsystems of the phonology. Recurring across a language family that spans a whole continent and many millennia of time depth, our findings provide one of the most compelling examples yet of Sapir\u2019s \u2018drift\u2019 hypothesis of non-accidental parallel development in historically related languages.<\/jats:p>","DOI":"10.3390\/e24040507","type":"journal-article","created":{"date-parts":[[2022,4,5]],"date-time":"2022-04-05T06:01:34Z","timestamp":1649138494000},"page":"507","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Evolution and Trade-Off Dynamics of Functional Load"],"prefix":"10.3390","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7533-8052","authenticated-orcid":false,"given":"Erich","family":"Round","sequence":"first","affiliation":[{"name":"Surrey Morphology Group, University of Surrey, Guildford GU2 7XH, UK"},{"name":"Ancient Language Lab, University of Queensland, St Lucia 4072, Australia"},{"name":"Max Planck Institute for the Science of Human History, D-07745 Jena, Germany"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6640-808X","authenticated-orcid":false,"given":"Rikker","family":"Dockum","sequence":"additional","affiliation":[{"name":"Department of Linguistics, Swarthmore College, Swarthmore, PA 19081, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7467-0467","authenticated-orcid":false,"given":"Robin J.","family":"Ryder","sequence":"additional","affiliation":[{"name":"CEREMADE, CNRS, UMR 7534, Universit\u00e9 Paris-Dauphine, PSL University, 75016 Paris, France"}]}],"member":"1968","published-online":{"date-parts":[[2022,4,5]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1080\/00437956.1952.11659416","article-title":"Function, structure, and sound change","volume":"8","author":"Martinet","year":"1952","journal-title":"Word"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"300","DOI":"10.1080\/00437956.1967.11435484","article-title":"The quantification of functional load","volume":"23","author":"Hockett","year":"1967","journal-title":"Word"},{"key":"ref_3","first-page":"43","article-title":"Quantifying the functional load of phonemic oppositions, distinctive features, and suprasegmentals","volume":"279","author":"Surendran","year":"2006","journal-title":"Amst. Stud. Theory Hist. Linguist. Sci."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Shannon, C.E. (1948). A mathematical theory of communication. Bell Syst. Tech. J., 27.","DOI":"10.1002\/j.1538-7305.1948.tb00917.x"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"179","DOI":"10.1016\/j.cognition.2013.03.002","article-title":"High functional load inhibits phonological contrast loss: A corpus study","volume":"128","author":"Wedel","year":"2013","journal-title":"Cognition"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"88","DOI":"10.1038\/scientificamerican0960-88","article-title":"The origin of speech","volume":"203","author":"Hockett","year":"1960","journal-title":"Sci. Am."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Honeybone, P., and Salmons, J. (2015). Tonoexodus, tonogenesis, and tone change. The Oxford Handbook of Historical Phonology, Oxford University Press.","DOI":"10.1093\/oxfordhb\/9780199232819.001.0001"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"698","DOI":"10.1353\/lan.2018.0040","article-title":"What tone teaches us about language","volume":"94","author":"Hyman","year":"2018","journal-title":"Language"},{"key":"ref_9","unstructured":"Dryer, M.S., and Haspelmath, M. (2013). Weight Factors in Weight-Sensitive Stress Systems. The World Atlas of Language Structures Online, Max Planck Institute for Evolutionary Anthropology."},{"key":"ref_10","unstructured":"Nespor, M., and Vogel, I. (1986). Prosodic Phonology, Foris."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"F\u00e9ry, C., and de Vijver, R. (2003). The independent nature of phonotactic constraints: An alternative to syllable-based approaches. The Syllable in Optimality Theory, Cambridge University Press.","DOI":"10.1017\/CBO9780511497926"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Cutler, A. (2012). Native Listening: Language Experience and the Recognition of Spoken Words, MIT Press.","DOI":"10.7551\/mitpress\/9012.001.0001"},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Bowern, C., and Evans, B. (2015). Sound change. The Routledge Handbook of Historical Linguistics, Routledge.","DOI":"10.4324\/9781315794013"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"453","DOI":"10.1017\/S0022226709990247","article-title":"Neutralization and anti-homophony in Korean","volume":"46","author":"Silverman","year":"2010","journal-title":"J. Linguist."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"4224","DOI":"10.1073\/pnas.1204678110","article-title":"Automated reconstruction of ancient languages using probabilistic models of sound change","volume":"110","author":"Hall","year":"2013","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Babinski, S., and Bowern, C. (2018). Mergers in Bardi: Contextual probability and predictors of sound change. Linguist. Vanguard, 4.","DOI":"10.1515\/lingvan-2017-0024"},{"key":"ref_17","first-page":"6","article-title":"On Functional Load and its Relation to the Actuation Problem","volume":"26","author":"Ceolin","year":"2020","journal-title":"Univ. Pa. Work. Pap. Linguist."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"125","DOI":"10.1002\/j.1834-4453.1996.tb00356.x","article-title":"Backtracking to Babel: The chronology of Pama-Nyungan expansion in Australia","volume":"31","author":"McConvell","year":"1996","journal-title":"Archaeol. Ocean."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"817","DOI":"10.1353\/lan.2012.0081","article-title":"Computational phylogenetics and the internal structure of Pama-Nyungan","volume":"88","author":"Bowern","year":"2012","journal-title":"Language"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"741","DOI":"10.1038\/s41559-018-0489-3","article-title":"The origin and expansion of Pama\u2014Nyungan languages across Australia","volume":"2","author":"Bouckaert","year":"2018","journal-title":"Nat. Ecol. Evol."},{"key":"ref_21","unstructured":"Butcher, A.R. (1999, January 1\u20137). What speakers of Australian Aboriginal languages do with their velums and why: The phonetics of the nasal\/oral contrast. Proceedings of the XIVth International Congress of the Phonetic Sciences, San Francisco, CA, USA."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"175","DOI":"10.1017\/S0025100304001719","article-title":"VC vs. CV syllables: A comparison of Aboriginal languages with English","volume":"34","author":"Tabain","year":"2004","journal-title":"J. Int. Phon. Assoc."},{"key":"ref_23","unstructured":"Harrington, J.M., and Tabain, M. (2006). Australian Aboriginal languages: Consonant-salient phonologies and the \u2018place-of-articulation imperative\u2019. Speech Production: Models, Phonetic Processes and Techniques, Psychology Press."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Koch, H., and Nordlinger, R. (2014). Sound patterns of Australian languages. The Languages and Linguistics of Australia: A Comprehensive Guide, Mouton de Gruyter.","DOI":"10.1515\/9783110279771"},{"key":"ref_25","unstructured":"Jepson, K., and Stoakes, H. (2015, January 10\u201314). Vowel duration and consonant lengthening in Djambarrpuyngu. Proceedings of the 18th International Congress of Phonetic Sciences, Glasgow, UK."},{"key":"ref_26","first-page":"293","article-title":"The pre-stopped nasal and lateral consonants of Arabana-Wangganguru","volume":"14","author":"Hercus","year":"1972","journal-title":"Anthropol. Linguist."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Loakes, D., Butcher, A., Fletcher, J., and Stoakes, H. (2008, January 22\u201326). Phonetically prestopped laterals in Australian languages: A preliminary investigation of Warlpiri. Proceedings of the 9th Annual Conference of the International Speech Communication Association Interspeech 2008, Brisbane, Australia.","DOI":"10.21437\/Interspeech.2008-20"},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Pensalfini, R., Guillemin, D., and Turpin, M. (2014). Prestopping of nasals and laterals is only partly parallel. Language Description Informed by Theory, John Benjamins.","DOI":"10.1075\/slcs.147"},{"key":"ref_29","unstructured":"Sutton, P. (1976). Wik reflections of Middle Paman phonology. Languages of Cape York, AIAS."},{"key":"ref_30","first-page":"357","article-title":"Kugu Nganhcara","volume":"Volume 5","author":"Dixon","year":"2000","journal-title":"Handbook of Australian Languages"},{"key":"ref_31","unstructured":"Hercus, L.A. (1992). A Nukunu Dictionary, Department of Linguistics, Australian National University."},{"key":"ref_32","first-page":"307","article-title":"Uradhi","volume":"Volume 3","author":"Dixon","year":"1983","journal-title":"Handbook of Australian Languages"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Bowern, C. (2022). Sound change. Oxford Handbook of Australian Languages, Oxford University Press.","DOI":"10.1093\/oso\/9780198824978.001.0001"},{"key":"ref_34","unstructured":"Sutton, P. (1976). Phonological developments in particular Northern Paman languages. Languages of Cape York, AIAS."},{"key":"ref_35","unstructured":"Sutton, P. (1976). Phonological developments in a Northern Paman language: Uradhi. Languages of Cape York, AIAS."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"360","DOI":"10.1080\/07268602.2018.1470457","article-title":"Lamalamic Root Structure: Erosion and Expansion","volume":"38","author":"Verstraete","year":"2018","journal-title":"Aust. J. Linguist."},{"key":"ref_37","unstructured":"Tryon, D., and Walsh, M. (1997). Pama-Nyungan reflexes in the Arandic languages. Boundary Rider: Essays in Honour of Geoffrey O\u2019Grady, Pacific Linguistics."},{"key":"ref_38","unstructured":"Simpson, J., Nash, D., Laughren, M., Austin, P., and Alpher, B. (2001). Basic vocabulary of the Arandic languages: From classification to reconstruction. Forty Years on: Ken Hale and Australian Languages, Pacific Linguistics."},{"key":"ref_39","unstructured":"Black, P.D. (1980). Norman Pama historical phonology. Papers in Australian Linguistics 13, Pacific Linguistics."},{"key":"ref_40","first-page":"273","article-title":"Olgolo syllable structure and what they are doing about it","volume":"1","author":"Dixon","year":"1970","journal-title":"Linguist. Inq."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"e324","DOI":"10.1353\/lan.2018.0070","article-title":"Language documentation twenty-five years on","volume":"94","author":"Seifart","year":"2018","journal-title":"Language"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"210","DOI":"10.1075\/dia.20004.mac","article-title":"Phylogenetic signal in phonotactics","volume":"38","author":"Bowern","year":"2021","journal-title":"Diachronica"},{"key":"ref_43","unstructured":"Austin, P.K. (1981). A Grammar of Diyari, South Australia, Cambridge University Press. Number 32 in Cambridge Studies in Linguistics."},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"McGregor, W. (1990). A Functional Grammar of Gooniyandi, John Benjamins. Number 22 in Studies in Language.","DOI":"10.1075\/slcs.22"},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Bowern, C. (2022). Phonotactics. Oxford Guide to Australian Languages, Oxford University Press.","DOI":"10.1093\/oso\/9780198824978.001.0001"},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Macklin-Cordes, J., and Round, E.R. (2022). Challenges of sampling and how phylogenetic comparative methods help: With a case study of the Pama-Nyungan laminal contrast. arXiv.","DOI":"10.1515\/lingty-2021-0025"},{"key":"ref_47","doi-asserted-by":"crossref","unstructured":"Garamszegi, L.Z. (2014). Modern Phylogenetic Comparative Methods and Their Application in Evolutionary Biology: Concepts and Practice, Springer.","DOI":"10.1007\/978-3-662-43550-2"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"1463","DOI":"10.1093\/bioinformatics\/btq166","article-title":"Picante: R tools for integrating phylogenies and ecology (version 1.8.2)","volume":"26","author":"Kembel","year":"2010","journal-title":"Bioinformatics"},{"key":"ref_49","first-page":"717","article-title":"Testing for phylogenetic signal in comparative data: Behavioral traits are more labile","volume":"57","author":"Blomberg","year":"2003","journal-title":"Evolution"},{"key":"ref_50","unstructured":"Bowern, C. (2015). Pama\u2013Nyungan phylogenetics and beyond [plenary address]. Lorentz Center Workshop on Phylogenetic Methods in Linguistics, Leiden University."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"534","DOI":"10.2307\/2409910","article-title":"Phylogenetic analyses of the correlated evolution of continuous characters: A simulation study","volume":"45","author":"Martins","year":"1991","journal-title":"Evolution"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"217","DOI":"10.1111\/j.2041-210X.2011.00169.x","article-title":"phytools: An R package for phylogenetic comparative biology (and other things)","volume":"3","author":"Revell","year":"2012","journal-title":"Methods Ecol. Evol."},{"key":"ref_53","doi-asserted-by":"crossref","unstructured":"Dockum, R. (2017, January 15\u201317). Phylogeny in phonology: How Tai sound systems encode their past. Proceedings of the 2017 Annual Meetings on Phonology, New York, NY, USA.","DOI":"10.3765\/amp.v5i0.4238"},{"key":"ref_54","unstructured":"Macklin-Cordes, J., and Round, E. (2015, January 4\u20136). High-definition phonotactics reflect linguistic pasts. Proceedings of the 6th Conference on Quantitative Investigations in Theoretical Linguistics, T\u00fcbingen, Germany."},{"key":"ref_55","unstructured":"Dockum, R. (2019). The Tonal Comparative Method: Tai Tone in Historical Perspective. [Ph.D. Thesis, Yale University]."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"267","DOI":"10.3758\/BF03204386","article-title":"Spoken word recognition processes and the gating paradigm","volume":"28","author":"Grosjean","year":"1980","journal-title":"Percept. Psychophys."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"e428","DOI":"10.1353\/lan.2019.0082","article-title":"Crosslinguistic evidence for a strong statistical universal: Phonological neutralization targets word-ends over beginnings","volume":"95","author":"Wedel","year":"2019","journal-title":"Language"},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"231","DOI":"10.1515\/flih-2019-0011","article-title":"Incremental word processing influences the evolution of phonotactic patterns","volume":"53","author":"Wedel","year":"2019","journal-title":"Folia Linguist."},{"key":"ref_59","unstructured":"Nordlinger, R., and Koch, H. (2014). Word structure in Australian languages. The Languages and Linguistics of Australia: A Comprehensive Guide, Walter de Gruyter."},{"key":"ref_60","unstructured":"Hamilton, P. (1996). Phonetic Constraints and Markedness in the Phonotactics of Australian Aboriginal Languages. [Ph.D. Thesis, University of Toronto]."},{"key":"ref_61","first-page":"35","article-title":"Swadesh lists are not long enough: Drawing phonological generalizations from limited data","volume":"16","author":"Dockum","year":"2019","journal-title":"Lang. Document. Descript"},{"key":"ref_62","unstructured":"Round, E.R., and Macklin-Cordes, J. (2019, January 1\u20135). Clouded vision: Why insights improve when uncertainty about data is made explicit, 2019. Proceedings of the 24th International Conference on Historical Linguistics, Canberra, Australia."},{"key":"ref_63","doi-asserted-by":"crossref","unstructured":"Gordon, M.K. (2016). Phonological Typology, Oxford University Press.","DOI":"10.1093\/acprof:oso\/9780199669004.001.0001"},{"key":"ref_64","unstructured":"Haudricourt, A.G. (1968, January 15\u201320). Les doubles transphonologisations simultan\u00e9es. Proceedings of the Actes du XIIe Congr\u00e8s International de Linguistique et de Philologie Romanes, Bucarest, Romania."},{"key":"ref_65","unstructured":"Keiler, A.R. (1971). Principles of historical phonology. A Reader in Historical and Comparative Linguistics, Holt, Rinehart and Winston."},{"key":"ref_66","unstructured":"Traugott, E., and Heine, B. (1991). Areal and universal dimensions of grammatization in Lahu. Approaches to Grammaticalization, John Benjamins."},{"key":"ref_67","first-page":"3181","article-title":"Re-evaluating phoneme frequencies","volume":"11","author":"Round","year":"2020","journal-title":"Front. Psychol."},{"key":"ref_68","unstructured":"Sapir, E. (1921). Language: An Introduction to the Study of Speech, Dover Publications."},{"key":"ref_69","unstructured":"Grierson, G.A. (1931). On the Modern Indo-Aryan Vernaculars, Indian Antiquary."},{"key":"ref_70","doi-asserted-by":"crossref","first-page":"295","DOI":"10.1086\/509488","article-title":"Drift and the grammaticalization divide between Northern and Southern Wakashan","volume":"72","author":"Fortescue","year":"2006","journal-title":"Int. J. Am. Linguist."},{"key":"ref_71","unstructured":"Croft, W. (2000). Explaining Language Change: An Evolutionary Approach, Longman."},{"key":"ref_72","doi-asserted-by":"crossref","unstructured":"Dahl, \u00d6. (2004). The Growth and Maintenance of Linguistic Complexity, John Benjamins Publishing.","DOI":"10.1075\/slcs.71"},{"key":"ref_73","doi-asserted-by":"crossref","unstructured":"Heine, B., and Kuteva, T. (2005). Language Contact and Grammatical Change, Cambridge University Press.","DOI":"10.1017\/CBO9780511614132"},{"key":"ref_74","doi-asserted-by":"crossref","first-page":"79","DOI":"10.1038\/nature09923","article-title":"Evolved structure of language shows lineage-specific trends in word-order universals","volume":"473","author":"Dunn","year":"2011","journal-title":"Nature"},{"key":"ref_75","doi-asserted-by":"crossref","unstructured":"Robbeets, M., and Cuyckens, H. (2013). Demystifying drift. Shared Grammaticalization, John Benjamins.","DOI":"10.1075\/slcs.132"},{"key":"ref_76","doi-asserted-by":"crossref","first-page":"711","DOI":"10.1093\/sysbio\/syw018","article-title":"Gene Tree Discordance Causes Apparent Substitution Rate Variation","volume":"65","author":"Mendes","year":"2016","journal-title":"Syst. Biol."},{"key":"ref_77","unstructured":"Iosad, P. (2021, January 14\u201318). Phonological convergence in North-western Europe. Proceedings of the 12th International Conference of Nordic and General Linguistics, Oslo, Norway."},{"key":"ref_78","unstructured":"Round, E.R. (2019, January 9\u201312). Getting Sapir\u2019s drift: Parallel evolution in linguistic as in biological systems. Proceedings of the Protolang 5, Lisbon, Portugal."},{"key":"ref_79","doi-asserted-by":"crossref","first-page":"239","DOI":"10.1038\/nrg.2016.11","article-title":"Causes of molecular convergence and parallelism in protein evolution","volume":"17","author":"Storz","year":"2016","journal-title":"Nat. Rev. Genet."},{"key":"ref_80","unstructured":"Hyman, L.M. (1973). Tonogenesis in Southeast Asia. Consonant Types and Tone, University of Southen California. Number 1 in Southern California Occasional Papers in Linguistics."},{"key":"ref_81","unstructured":"Jenner, P.N., Thompson, L.C., and Starosta, S. (1976). The register problem in fifteen Mon-Khmer languages. Austroasiatic Studies, Univ of Hawaii Press."},{"key":"ref_82","unstructured":"Dockum, R., and Gehrmann, R. (2021, January 7\u201310). The East Asian Voicing Shift and its Role in the Origins of Tone and Register. Proceedings of the 95th Annual Meeting of the Linguistic Society of America, San Francisco, CA, USA."}],"container-title":["Entropy"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1099-4300\/24\/4\/507\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T22:49:50Z","timestamp":1760136590000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1099-4300\/24\/4\/507"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,4,5]]},"references-count":82,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2022,4]]}},"alternative-id":["e24040507"],"URL":"https:\/\/doi.org\/10.3390\/e24040507","relation":{},"ISSN":["1099-4300"],"issn-type":[{"value":"1099-4300","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,4,5]]}}}