to be more labile, appearing several times within Indo-European languages, several times in American languages, and several times in Papuan families. That may indicate that rather than a trait unique to some language families, tone is a latent feature of most language families that may more easily arise and disappear as languages change over time. A 2015 study by Caleb Everett argued that tonal languages are more common in hot and humid climates, which make them easier to pronounce, even when considering familial relationships. If the conclusions of Everett's work are sound, this is perhaps the first known case of influence of the environment on the structure of the languages spoken in it. The proposed relationship between climate and tone is controversial, and logical and statistical issues have been raised by various scholars. Tone and inflection Tone has long been viewed as merely a phonological system. It was not until recent years that tone was found to play a role in inflectional morphology. Palancar and Léonard (2016) provided an example with Tlatepuzco Chinantec (an Oto-Manguean language spoken in Southern Mexico), where tones are able to distinguish mood, person, and number: In Iau language (the most tonally complex Lakes Plain language, predominantly monosyllabic), nouns have an inherent tone (e.g. be˧ 'fire' but be˦˧ 'flower'), but verbs don't have any inherent tone. For verbs, a tone is used to mark aspect. The first work that mentioned this was published in 1986. Example paradigms: Tones are used to differentiate cases as well, as in Maasai language (a Nilo-Saharan language spoken in Kenya and Tanzania): Certain varieties of Chinese are known to express meaning by means of tone change although further investigations are required. Examples from two Yue dialects spoken in Guangdong Province are shown below. In Taishan, tone change indicates the grammatical number of personal pronouns. In Zhongshan, perfective verbs are marked with tone change. Taishan Zhongshan The following table compares the personal pronouns of Sixian dialect (a dialect of Taiwanese Hakka) with Zaiwa and Jingpho (both Tibeto-Burman languages spoken in Yunnan and Burma). From this table, we find the distinction between nominative, genitive, and accusative is marked by tone change and sound alternation. Phonetic notation There are several approaches to notating tones in the description of a language. A fundamental difference is between phonemic and phonetic transcription. A phonemic notation will typically lack any consideration of the actual phonetic values of the