This post was originally started and mostly written a few years ago. It is refined, expanded, and published now. (I've now cleared my backlog of draft posts.)
Languages with Complex Tone Systems
Languages With Simple Tone Systems
Languages Without Tone Systems
Languages with labial-velar consonants in yellow;
languages with clicks in red and black.
Languages with glottal consonants other than ejectives
Purple and yellow have implosives only;
red and white have glottalized resonants only;
green and aqua have implosives and glottalized resonants.
Charts via WALS Online.
What is a tonal language?
In a tonal language, tone is the term used to describe the use of pitch patterns to distinguish individual words or the grammatical forms of words, such as the singular and plural forms of nouns or different tenses of verbs.
Tonality appears to be a part of a total phoneme set for a language which also includes a language's inventory of consonants, glottal stops, vowels, and click sounds.
Tonality tends to be associated with a larger number of other phonemes as well.
* The average language with a complex tone system has 26.0 consonants and 7.05 vowels, for a total of 33.05 phonemes.
* The average language with a simple tone system has 23.3 consonants and 6.28 vowels, for a total of 29.58 phonemes.
* The average language with no tone system has 22.1 consonants and 5.58 vowels, for a total of 27.68 phonemes.
Tonal languages also tend to be more likely to have implosive consonants (a type of glottal consonant), glottal resonant consonants, labial-velar consonants, and linguistic click consonants.
Where Are Tonal Languages Spoken?
As the charts at the top of this post demonstrate, tone languages tend to be more vastly common in places that with tropical (or at least subtropical) climates and very rare elsewhere.
Languages with simple tone systems show a similar, but less pronounced tendency. All of the tonal languages outside tropical and subtropical areas have only simple tone systems.
Some of the more controversial cases are arguable cases of simple tone systems in places where tonal languages are rare. A dozen of the languages classified as having simple tone systems are among the most geographically atypical and are only marginally tonal to the extent that they arguably would be more properly classified as non-tonal. These include Norwegian, Japanese, Ainu and Oneida (Iroquoian; New York State).
Much of South Asia, however, despite having many languages, has a tropical or subtropical climate, but appears to have no languages with a complex tone system among its many Indo-European, Dravidian, or Austroasiatic languages, although it does have a handful of Sino-Tibetan languages with simple tone systems in the highlands found in the Himalayas and in the far northeast of the subcontinent.
There are definitional issues about what constitutes a language with a complex tone system, a simple tone system or no tone system. WALS explains its definitions (emphasis added):
The first distinction made in this chapter is between languages with and languages without tones. For most languages it is easy to determine if the language does or does not make use of tone, but there are surprisingly sharp disagreements in certain cases.
For example, Dar Fur Daju (Nilo-Saharan; Sudan) is reported as non-tonal in one source but transcribed with three tone levels in another. Ket (Yeniseian; northern Siberia) is described as having none, two, four or eight tones by different authors (there are some differences in the dialects being described, but this does not account for the differences of opinion on the tonal status of the language). Both these languages have been counted as non-tonal in the present chapter since the opinion that they lack tones seems to be the most well-supported (see Thelwall 1981 and Feev 1998 respectively).
Other languages have clear word-level pitch phenomena but with limited function, or with roles that look more like stress in that they highlight a particular syllable of a word. Norwegian, Japanese, Ainu and Oneida (Iroquoian; New York State) are among languages of this kind. These languages are classified here as tonal, but are perhaps only marginally so.
Of the 526 languages included in the data used for this chapter, 306 (58.2%) are classified as non-tonal. This probably underrepresents the proportion of the world’s languages which are tonal since the sample is not proportional to the density of languages in different areas.
For example, from the large Niger-Congo family of Africa there are 68 languages in the sample, 5 of which are nontonal (Swahili, Diola-Fogny, Koromfe, Wolof and Bisa) and the remainder tonal. The Ethnologue (Grimes 2000) lists 1489 Niger-Congo languages, so less than 5% of the Niger-Congo languages are included.
Of the Indo-European languages of western and central Europe, 16 are included (5 Romance, 3 Germanic, 3 Slavic, 2 Celtic, 1 Baltic, Greek, and Albanian). In these Indo-European groups the Ethnologue lists a total of 145 languages (7 Celtic, 58 Germanic, 48 Italic, 18 Slavic, 7 Greek, 4 Albanian, and 3 Baltic languages), so that over 10% of the Western European languages listed are included, only two of which are tonal or marginally so and the rest non-tonal.
If, correspondingly, 10% of the Niger-Congo family had been included, 80 additional tone languages would have been included.
Languages without tones predominate in the western part of the Eurasian landmass, including South Asia, in the more southerly regions of South America, and in the coastal area of northwestern North America. In this last area great genealogical diversity exists among the indigenous languages, but tone is almost entirely absent. In addition, no Australian language has been reported to be tonal.
The languages with tones are divided into those with a simple tone system — essentially those with only a two-way basic contrast, usually between high and low levels — and those with a more complex set of contrasts.
About a quarter of the languages (132, or 25.1%) have simple tone systems. This includes 12 languages which appear to meet the definition of being tonal only marginally. With better information a few of these might end up being classed as non-tonal.
Less than a fifth (88, or 16.7%) have complex tone systems. Tone languages have marked regional distributions. Virtually all the languages in Africa are tonal, with the greater number having only simple tone systems, although more complex systems are not unusual, especially in West Africa. Languages with complex tone systems dominate in an area of East and Southeast Asia. Several clusters of languages with tones occur in South, Central and North America. A number of the languages of New Guinea are also tonal, or at least marginally so.
Tonality Appears To Be Primarily An Areal Rather Than A Language Family Based Property Of Languages
There are language families in which some languages are tonal, while other are not.
As noted above, two Indo-European languages arguably have simple tone systems, although at least one of these is a marginal case with a dubious classification.
Only five of Africa's Niger-Congo languages do not have tone systems.
Within the Afroasiatic language family, tonal languages appear in the Omotic, Chadic, and Cushitic branches of Afroasiatic (the Southern tier of Afroasiatic languages, mostly in Ethiopia and the African Sahel), according to Ehret (1996), but the Semitic, Berber, and Egyptian branches do not use tones phonemically.
Most Austroasiatic languages are tonal, but not the Munda languages of South Asia and not five of the lesser known Austroasiatic languages of Vietnam and Laos.
The Austronesian languages aren't uniform with regard to tonality either: "Unlike in the languages of Mainland Southeast Asia, tonal contrasts are extremely rare in Austronesian languages. Exceptional cases of tonal languages are Moklen and a few languages of the Chamic, South Halmahera–West New Guinea and New Caledonian subgroups."
The locations have temperatures and humidities that influence sound transmission through the air, and have terrain influences (e.g. tree density) that impact how far away you would need words you speak to carry best. So, one theory is that tone languages arise in places where the sound transmission qualities of the air and terrain favor them.
The correlations between interpopulation genetic and linguistic diversities are mostly noncausal (spurious), being due to historical processes and geographical factors that shape them in similar ways. Studies of such correlations usually consider allele frequencies and linguistic groupings (dialects, languages, linguistic families or phyla), sometimes controlling for geographic, topographic, or ecological factors.
Here, we consider the relation between allele frequencies and linguistic typological features. Specifically, we focus on the derived haplogroups of the brain growth and development-related genes ASPM and Microcephalin, which show signs of natural selection and a marked geographic structure, and on linguistic tone, the use of voice pitch to convey lexical or grammatical distinctions.
We hypothesize that there is a relationship between the population frequency of these two alleles and the presence of linguistic tone and test this hypothesis relative to a large database (983 alleles and 26 linguistic features in 49 populations), showing that it is not due to the usual explanatory factors represented by geography and history. The relationship between genetic and linguistic diversity in this case may be causal: certain alleles can bias language acquisition or processing and thereby influence the trajectory of language change through iterated cultural transmission.
Dan Dediu and D. Robert Ladd, "Linguistic tone is related to the population frequency of the adaptive haplogroups of two brain size genes, ASPM and Microcephalin" 104 (26) PNAS 10944-10949 (June 26, 2007). https://doi.org/10.1073/pnas.0610848104
The size of human brain tripled over a period of approximately 2 million years (MY) that ended 0.2-0.4 MY ago. This evolutionary expansion is believed to be important to the emergence of human language and other high-order cognitive functions, yet its genetic basis remains unknown. An evolutionary analysis of genes controlling brain development may shed light on it. ASPM (abnormal spindle-like microcephaly associated) is one of such genes, as nonsense mutations lead to primary microcephaly, a human disease characterized by a 70% reduction in brain size. Here I provide evidence suggesting that human ASPM went through an episode of accelerated sequence evolution by positive Darwinian selection after the split of humans and chimpanzees but before the separation of modern non-Africans from Africans. Because positive selection acts on a gene only when the gene function is altered and the organismal fitness is increased, my results suggest that adaptive functional modifications occurred in human ASPM and that it may be a major genetic component underlying the evolution of the human brain.