The dog was the first animal to be domesticated. This animal shared our lives and environments even before the invention of agriculture and any other animal husbandry. In ancient times, the dog was the only domestic animal to accompany humans to every continent.
The island of Madagascar is only a short distance from the African continent. Linguistic and genetic evidence show that the island was initially colonised by Austronesian-speaking people originating from Indonesia 1500–2000 years ago. Human migrations from Africa have resulted in a population that has approximately equal genetic contributions from Indonesia and Africa. Austronesian travellers took along their dogs, pigs and chickens on all their journeys.
Our study aimed to investigate the genetic ancestry of Madagascan dogs in an effort to better understand this interesting part of the initial worldwide dispersal of dogs.
In search of dog DNA
We sampled 145 dogs in Madagascar and nearly 2500 dogs globally. Our study sequenced a specific segment of the mitochondrial genome that allows for the identification of maternal lineages. It also traces populations back to their ancestral origins. Madagascan dogs were compared to their potential ancestral populations in islands southeast of Asia and sub-Saharan Africa.
The results did not follow the genetic structure of the Madagascan human population. Madagascan dogs don’t show the Austronesian signature typical of Indonesia and Polynesia. Their origin is traced entirely from Africa.
The Indonesian sample actually included dogs from within a 200km radius from Banjarmas in southeast Borneo. This area has been pinpointed as the origin of the Austronesian language spoken in Madagascar. It is also the likely ancestral pool of the first Malagasy colonisers.
Our findings mean that dogs weren’t introduced to Madagascar by Austronesian-speaking people. So, where did they come from?
Madagascan dogs are African
The genetic similarity between Madagascar and Africa suggests that the source of Madagascan dogs may be located somewhere along the African east coast.
The study was unable to pinpoint any specific region across sub-Saharan Africa. Instead, we found comparable similarity between Madagascan dogs and several populations across sub-Saharan Africa.
Given the long history of sea trade between the African east coast, the Persian Gulf region and later the Indian subcontinent, genetic contributions from India or Southwest Asia are also possible. However, we did not find clear evidence supporting it.
There was a slightly higher degree of European influence, but this probably reflects historical contacts between Madagascar and Europe in the recent colonial era.
Breaking assumptions with dogged determination
The study’s results suggest that dogs were not brought to Madagascar by the initial Austronesian-speaking colonisers on their transoceanic voyage. They arrived at a later stage, together with human migration and cultural influence from Africa. This is in agreement with the archaeological evidence for an African influence of the Madagascan material culture.
The African origin of domestic dogs in Madagascar is also supported by linguistic evidence showing that the word for dog is adopted from African Bantu languages.
It is surprising that there is an absence of the Austronesian genetic signature in Madagascan dogs. Dogs were important domestic animals in Austronesian culture. In the colonisation of major new areas, they were generally brought along. The genetic diversity of Madagascan dogs is higher than other island dog populations possibly related with the Austronesian expansion.
This relates to dogs like the Australian dingo and ancient Polynesian dogs. Dogs were brought to Madagascar from Africa through a process extended over time, instead of a limited number of individuals arriving a few times to a new territory.
This study provides the first indications to the origins of dogs in Madagascar. It contributes to the emergent global picture of the dispersal of dogs around the world. Future studies that include more extensive sampling of coastal eastern Africa and analysis of additional genomic regions will certainly contribute to further solve this puzzle.
Clarification of the African or Indonesian origins of other domestic animals related to the Austronesian culture like the pig and the chicken will also contribute to better understand the ancestral colonisation of Madagascar.
Barbara van Asch does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.
Authors: The Conversation