A new paper on dingoes came out last winter which was in my “to-read” bookmarks, and I finally around to it. It’s open access, Genomic regions under selection in the feralization of the dingoes:
Dingoes are wild canids living in Australia, originating from domestic dogs. They have lived isolated from both the wild and the domestic ancestor, making them a unique model for studying feralization. Here, we sequence the genomes of 10 dingoes and 2 New Guinea Singing Dogs. Phylogenetic and demographic analyses show that dingoes originate from dogs in southern East Asia, which migrated via Island Southeast Asia to reach Australia around 8300 years ago, and subsequently diverged into a genetically distinct population. Selection analysis identifies 50 positively selected genes enriched in digestion and metabolism, indicating a diet change during feralization of dingoes. Thirteen of these genes have shifted allele frequencies compared to dogs but not compared to wolves. Functional assays show that an A-to-G mutation in ARHGEF7 decreases the endogenous expression, suggesting behavioral adaptations related to the transitions in environment. Our results indicate that the feralization of the dingo induced positive selection on genomic regions correlated to neurodevelopment, metabolism and reproduction, in adaptation to a wild environment.
The selection analysis is probably correct on some level, but I’m not sure this paper changes my priors much. The problem is so much of the analysis is based on the sequences of European dogs as your reference population. They allude to this issue in the paper. Also, research groups using ancient DNA are suggesting that the separation and domestication of dogs from the broader wolf lineage is more complex and episodic than we thought a decade ago. Basically, I assume that feralization is going on, but the details are to be worked out. We need to understand the context of Asian dogs better than we do now.
That being said, the 8,300 date is interesting. In the paper, they use both mtDNA and whole-genome sequences to come to this conclusion. One should be careful about taking genomic dating too literally, but this is 5,000 years earlier than the fossils we have in Australia. Nevertheless, the phylogeny is interesting, as the dingos are where you’d expect. They’re a clade with New Guinea singing dogs. And then it’s Indonesian dogs. And finally, it’s along with Southeast Asian dogs.
If the dingos came to Australia 8,000 years ago, then that’s well before agriculture. And, it is evidence of maritime connections between hunter-gatherer populations.
Or, the divergence could be evidence of “deep structure” within Southeast Asia. That is, these various lineages were separate and diversified before being dispered more recently.
In either case, these are important questions.
There’s scholarship on the maritime connections in the Aegean prior to agriculture isn’t there? So this doesn’t seem like a stretch.
Dr. Eske Willerslev has stated that there is a recent but small genetic input into Australian aboriginals. I forgot if he mentioned the date of the admixture. Does anyone know if this ‘recent’ input in Australian aboriginals has been dated or not?
“If the dingos came to Australia 8,000 years ago… it is evidence of maritime connections between hunter-gatherer populations”
Monash Uni puts a land bridge over Torres Strait down to about 8,500 BP…. http://sahultime.monash.edu.au/explore.html
From the paper (citations and references omitted):
“Based on a mutation rate of 1.3 × 10^−9 per site per year and a generation time of 3 years, our analysis indicates that the split between dingoes and Indonesian village dogs occurred around 8300 (CI: 5400–11,200) years ago and that, before that, Indonesian village dogs diverged from the indigenous dogs from southern East Asia around 9900 (CI: 6500–12,700) years ago.”
The more recent end of the split date confidence interval, which ranges from 9200 BCE to 1400 BCE with a best fit point of 6300 BCE, would be a much better fit to the conventional interpretation of a Neolithic maritime source (probably Austronesian) for the arrival of Dingos in Australia.
Austronesian expansion is conventionally dated as beginning ca. 3000 BCE to 1500 BCE, so the recent end of the genetic confidence interval would fit pretty well, without having to consider atypical hunter-gather roles.