New evidence confirms Indigenous languages have a common source, but how they spread remains a mystery

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Have you ever wondered about the relationships between Australia's numerous Indigenous languages and the history behind these connections?

Just how old are the languages we speak today and where did they come from? Our research offers some insights - and these insights raise some new and intriguing questions.

It has been observed, for several decades, that the indigenous languages of continental Australia all share a common origin - Proto-Australian.

However, without thorough testing, it's difficult to determine whether these similarities can be attributed to a direct inheritance from a common ancestral language or some other mechanism, like borrowing, that wouldn't require a single ancestral language.

The first evaluation of the Proto-Australian hypothesis—shows it is supported. It is most likely that Proto-Australian was spoken about 6,000 years ago in the Northern Territory's Top End. When it spread across the Australian mainland, it replaced all the languages that had been spoken previously.

One big question is how this spread happened. Language spread is generally associated with population movements or developments in economy and technology. But there is no clear evidence for population movement or economic and technological change in the past 10,000 years.

It seems we need to create new frameworks for understanding how language evolved, and Australian prehistory.

Language families

Relationships between languages are determined by identifying shared words and similarities in language structure. Languages which exhibit similarities in structure are classified as part of a language family; languages not exhibiting such similarities are not considered part of that family.

One of the daughter families of Proto-Australian, (PPN), is significantly more widespread than the others, covering nearly 90% of the continent.

Several of these forms go on to form small families. Others are isolates, with no close relatives.

The region with the most isolated languages is the most culturally diverse. Within Australia, the Top End is this area. As a basic rule, the region with the greatest diversity is typically the earliest homeland of a common ancestral language. Therefore, the Top End is likely the earliest homeland of Proto-Australian.

In the Pama-Nyungan languages, various types are found:

• Amurdak: mara
• Bardi: marla
• Gajirrabeng: marla
• Ganggalida: marl
• Gija: marla
• Gooniyandi: marla
• Kayardild: marl
• Lardil: marl
• Ngandi: mar
• Nyulnyul: marl
• Yawuru: marla

Discovering similarities doesn't give us a precise timeline for when the original language was spoken as a single language, but there aren't any reliable examples dating back more than 10,000 years.

Language diversity is a fundamental characteristic of human language. Over time, unique characteristics of spoken languages will diverge completely. Considering the continent has been inhabited for at least 50,000 years, it's predicted that numerous unrelated languages have developed in Australia.

This prediction can be seen in two key examples: Tasmania, which was cut off from the mainland about 14,000 years ago, and the Tiwi Islands, which became separate about 6,000 years ago, thereby preventing language diffusion to either of these islands since then.

Neither the Tasmanian nor the Tiwi languages are related to the ones spoken on the mainland. This is in agreement with the prediction that languages typically lose similarities at standard rates of diversification.

Standard rates of diversification suggest that there should be many unrelated languages on the continent. However, this is not the case. Therefore, it's likely that Proto-Australian spread across the entire continent after the Tiwi Islands separated.

A big question

The question of why and how a particular language became so widely spoken is a significant one. Typically, when a language becomes widespread, related social changes often accompany it - such as population growth and movement, or innovations in the economy and technology. However, there is currently no direct evidence of these changes in this case.

Suggestions about population movements can be tested against genetic studies, and ideas about population growth or economic and technological improvements can be tested against the archaeological record.

There appears to be a notable inconsistency in genetic information available, yet no indication of substantial genetic alterations over the past 10,000 years.

It's believed that a single founding population existed, which branched off between 33,000 and 10,000 years ago, with genetic exchange originating from the northeastern part of the continent spreading throughout the rest of the continent over the last 10,000 years.

Suggests a founding population around 50,000 years ago, which quickly spread to all coastal areas by 45,000 years ago. This rapid spread was followed by ongoing diversification in place, with no indication of significant population migration.

Suggests that the gut microbiome diverged between 26,000-35,000 years ago, with very little evidence to indicate the transfer of bacteria between individuals.

Despite significant shifts in land use over the past 10,000 years in various regions, the evidence suggests that there is no clear evidence for simultaneous changes across the entire continent, nor is there evidence of only one-way change.

Approximately 4,000 to 8,000 years ago. However, it is highly unlikely that a single economic shift would lead to the replacement of languages across an entire continent. Moreover, the presence of dingoes on the Tiwi Islands indicates that the spread of the dingo does not match the spread of the supposed Proto-Australian language.

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On the mainland in Australia, the only languages spoken are those that are related to the original Proto-Australian language. This is quite unusual, which raises a good question, but unfortunately without any good answers, prompting us to re-examine our models.

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Provided by The Conversation

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