Last week I begged for a Malagasy genotype. I didn’t quite get that, but I got the second best thing: a part Malagasy-genotype. I decided to take it for a spin.
But first some preliminaries. Here’s what we know about this individual (or what this individual knows):
– 25% French (paternal grandfather)
– 18.75% West African? 6.25% French? (paternal grandmother French Antilles)
– 19% Indian Muslim Bohras from Bombay + 6.25% Malagas, Sakalava tribe, royal family of Mahajanga (maternal grand -father)
– 25% Malagasy (Sakalava, maternal grandmother mtDNA haplogroup M23)
This is a very mixed individual in terms of ancestry. As for the Malagasy people, we know both a lot and a little about them. They’re a hybrid population, more or less, of Austronesians with a very close connection to the to the Dayaks of southern Borneo. I have hypothesized that these Austronesians were part of a circum-Indian ocean trading network which was marginalized by the rise of Islam in the second half of the first millennium. Such an early date would explain why the Malagasy seem to have been only lightly touched by Indic cultural influences, let alone Islamic ones. There is also the African component to their ancestry, which is more prominent in the lowland populations to the west of the island of Madagascar. The Sakalava are a somewhat more African group (as opposed to the Merina of the eastern highlands, who are more Austronesian).
Below are some results from ADMIXTURE and PCA generated with EIGENSOFT. Most of the PCA plots were not too useful, because I didn’t fine-tune the populations ahead of time too much (this is a first pass), so I didn’t post them. The ADMIXTURE runs are those which seem highly informative to me. There were three data sets into which I merged the part-Malagasy individual:
– #1, A Southeast Asian focused one, using mostly the Pan-Asian Consortium populations
– #2, An Asian focused data set which used the HGDP
– #3, An African focused data set which used the Henn et al. populations as well as some HGDP ones
Markers show populations sampled by HUGO Pan-Asian SNP Consortium
The Pith: Southeast Asia was settled by a series of distinct peoples. The pattern of settlement can be discerned in part by examination of patterns of genetic variation. It seems likely that Austro-Asiatic populations were dominant across the western half of Indonesia before the arrival of Austronesians.
About a year and a half ago I reviewed a paper in Science which did a first pass through some of the findings suggested by the HUGO Pan-Asian SNP Consortium data set, which pooled a wide range of Asian populations. You can see the locations on the map above (alas, the labels are too small to read the codes). The important issue in relation to this data set is that it has a thick coverage of Southeast Asia, which is not well represented in the HGDP. Unfortunately there are only ~50,000 markers, which is not optimal for really fine-grained intra-regional analysis in my opinion. But better than nothing, and definitely sufficient for coarser scale analysis.
A few things have changed since I first reviewed this paper. First, I pulled down a copy of the Pan-Asian SNP data set. I’m going to play with it myself soon. Second, after reading Strange Parallels, volume 1 and 2, I know a lot more about Southeast Asian history. Finally, the possibility of archaic admixture amongst Near Oceanians makes the genetics of the regions which were once Sundaland and Sahul of particular interest.