The human colonization of Australia and Near Melanesia

Continuing with the joint series of articles on the expansion of Homo sapiens, David Sánchez published last week an interesting piece[es] on the original colonization of Australia and Papua at Noticias de Prehistoria – Prehistoria al Día, which I’ll try to synthesize here.

Earliest evidences of human occupation of Australia and Near Melanesia (all before 30 Ka BP)

Maybe the most interesting detail is that Lake Mungo 3 has dates that clearly establish a colonization of the continent at least 60,000 years ago:

81.000 +- 21.000 U (Uranium series)
62.000 +- 6.000 ESR/U (Electron spin resonance/Uranium)
61.000 +- 2.000 OSL (Optical Stimulated luminiscence)
40.000 +- 2.000 OSL (Optical Stimulated luminiscence)

The sites of Nauwalbila I and Malakunanja II have provided similar dates: 60-50 Ka BP (OSL) and 61,000 BP +9,000/-13,000 (TL) respectively. So we can safely discard the conservative approach that only allowed for at most 50 Ka as earliest colonization boundary for the Oceanian continental landmass. 

The depiction of a Genyornis, giant duck-like bird extinct before 40 Ka, in Australian rock art ago also supports a very early date for the settlement of Australia. In Highland Papua human presence is also confirmed to at least 49 Ka ago, as I reported in 2010.

Naturally the settlers must have arrived by sea, the most commonly accepted candidate for such a vessel is a humble raft still used by some Papuan populations and which has parallels in Southern Asia (also still in use in some places):

Such a journey was attempted with a similar but larger raft, equipped with a simple sail named Nale Tasih 2. This craft had no trouble in reaching the continental platform of Australia from Timor in just six days and they actually managed to reach the modern Australian coast, although they desisted of beaching by night in the middle of a storm in an area infested by the largest crocodiles on Earth, being evacuated by the coastguard instead (the barge was later recovered in perfect state).

 

The other red cell disease that protects against the other malaria

Oval red cells (CC The New Messiah)

It is generally well known that the sickle-cell disease, relatively common in parts of Africa, or rather its associated allele when heterozygous, has a protective effect against malaria, specifically to the variant caused by Plasmodium falciparium.

But there is at least another adaption to another kind of malaria: the one caused by P. vivax. This one, the SE Asian ovalocytosis (SAO), has only been discovered and studied in the last years and seems to exist only in some populations of Malaysia and Papua. This study confirms that the SAO defect effectively protects against P. vivax.

Ana Rosanas Urgell et al., Reduced Risk of Plasmodium vivax Malaria in Papua New Guinean Children with Southeast Asian Ovalocytosis in Two Cohorts and a Case-Control Study. PLoS Medicine 2012. Open access ··> LINK [doi:10.1371/journal.pmed.1001305] 

Abstract

Background

The erythrocyte polymorphism, Southeast Asian ovalocytosis (SAO) (which results from a 27-base pair deletion in the erythrocyte band 3 gene, SLC4A1Δ27) protects against cerebral malaria caused by Plasmodium falciparum; however, it is unknown whether this polymorphism also protects against P. vivax infection and disease.

Methods and Findings

The association between SAO and P. vivax infection was examined through genotyping of 1,975 children enrolled in three independent epidemiological studies conducted in the Madang area of Papua New Guinea. SAO was associated with a statistically significant 46% reduction in the incidence of clinical P. vivax episodes (adjusted incidence rate ratio [IRR] = 0.54, 95% CI 0.40–0.72, p<0.0001) in a cohort of infants aged 3–21 months and a significant 52% reduction in P. vivax (blood-stage) reinfection diagnosed by PCR (95% CI 22–71, p = 0.003) and 55% by light microscopy (95% CI 13–77, p = 0.014), respectively, in a cohort of children aged 5–14 years. SAO was also associated with a reduction in risk of P. vivax parasitaemia in children 3–21 months (1,111/µl versus 636/µl, p = 0.011) and prevalence of P. vivax infections in children 15–21 months (odds ratio [OR] = 0.39, 95% CI 0.23–0.67, p = 0.001). In a case-control study of children aged 0.5–10 years, no child with SAO was found among 27 cases with severe P. vivax or mixed P. falciparum/P. vivax malaria (OR = 0, 95% CI 0–1.56, p = 0.11). SAO was associated with protection against severe P. falciparum malaria (OR = 0.38, 95% CI 0.15–0.87, p = 0.014) but no effect was seen on either the risk of acquiring blood-stage infections or uncomplicated episodes with P. falciparum. Although Duffy antigen receptor expression and function were not affected on SAO erythrocytes compared to non-SAO children, high level (>90% binding inhibition) P. vivax Duffy binding protein–specific binding inhibitory antibodies were observed significantly more often in sera from SAO than non-SAO children (SAO, 22.2%; non-SAO, 6.7%; p = 0.008).

Conclusions

In three independent studies, we observed strong associations between SAO and protection against P. vivax malaria by a mechanism that is independent of the Duffy antigen. P. vivax malaria may have contributed to shaping the unique host genetic adaptations to malaria in Asian and Oceanic populations.

 

Evidence for New Guinea settlement 49,000 years ago

New findings in Papua Highlands reveal that people were already there at least as early as 49,000 years ago, living 2000 meters above sea level and using characteristic waisted axes (left), which they probably used to fell down trees and make convenient clearings. 

Previous research by the same team had located sites as old as 41,000 years near the coast.

Starch grains found on the axes are from yam (Dioscorea sp.), a tuber that does not grow at such high altitudes. Other vegetable remains found at the sites are charred nut shells from Pandamus sp., a high altitude tree that is used through Oceania for a variety of purposes: food, medicine, housing material, clothing, etc. Bones fragments from unidentified animals have also been found.

Lead researcher Glenn Summerhayes suggests that clearing was done on purpose, so medicinal plants could grow. He also suggests that some sort of clothing must have been used in order to ward off pneumonia (temperatures at such altitudes vary along the day between the nice 20 degrees Celsius at noon to freezing point at night).

Sources: Science News, DNA.

Ref. G. Summerhayes et al., Human Adaptation and Plant Use in Highland New Guinea 49,000 to 44,000 Years Ago. Science 2010. Pay per view.