[A]round 1,000 years ago, both stalagmites' calcium carbonate composition shifted suddenly and completely, from carbon isotope ratios typical of trees and shrubs, to those more consistent with grassland, within just 100 years.From here.
The paper is Stephen J. Burns, et al., "Rapid human-induced landscape transformation in Madagascar at the end of the first millennium of the Common Era.", Quaternary Science Reviews (2016).
UPDATE March 2, 2016: The abstract to the paper reveals that the dates are actually a bit earlier than 1,000 years ago, which helps to reconcile the archaeological record which favors a date somewhat earlier than 1000 CE for Austronesian arrival in Madagascar and this new data point. The abstract states:
The environmental impact of the early human inhabitants of Madagascar remains heavily debated. We present results from a study using two stalagmites collected from Anjohibe Cave in northwestern Madagascar to investigate the paleoecology and paleoclimate of northwestern Madagascar over the past 1800 years. Carbon stable isotopic data indicate a rapid, complete transformation from a flora dominated by C3 plants to a C4 grassland system. This transformation is well replicated in both stalagmites, occurred at 890 CE and was completed within one century. We infer that the change was the result of a dramatic increase in the use of fire to promote the growth of grass for cattle fodder. Further, stalagmite oxygen isotope ratios show no significant variation across the carbon isotope excursion, demonstrating that the landscape transformation was not related to changes in precipitation. Our study illustrates the profound impact early inhabitants had on the environment, and implies that forest loss was one trigger of megafaunal extinction.It also isn't implausible to think that the use of fire to cover forest to grassland wouldn't have begun immediately upon their arrival. They would have used the modest amount of existing grassland on the island at first and would have cleared more land only after their growing herds strained the carrying capacity of the existing grasslands.
17 comments:
That makes sense as it coincides with extinctions and is the most likely date for an Austronesian arrival. The question that then arises is: were there any people on Madagascar earlier than that. My feeling is no.
There is pretty solid recently discovered archaeological evidence of human habitation in Madagascar ca. 1000 BCE, about two thousand years earlier, which had a very minimal ecological impact, that I wrestle with in this post from July of 2013.
These were probably hunter-gatherers who lacked sufficient critical mass to preserve enough of their skills to make a long term impact, perhaps arriving after being cast adrift in a storm or something like that. They may very well have died out entirely before the Austronesian population arrived.
The first wave people were analogous to the Roanoke settlement (assuming that they died out entirely) or to the Tasmanians (whose cultural sophistication declined precipitously when they were isolated from mainland Australia by water).
Historical reality shows little respect for Occam's Razor, although it is generally true that the nuances that Occam's Razor disfavors tend to be footnotes of history with no enduring impact like this one.
Correction: The first modern human relics in Madagascar date to 2000 BCE.
"had a very minimal ecological impact, that I wrestle with in this post from July of 2013".
And my comments in answer to that post still stand.
"These were probably hunter-gatherers who lacked sufficient critical mass to preserve enough of their skills to make a long term impact"
In fact so few in numbers they were unable to form a long-term population. If they had been able to do so population numbers would have increased exponentially until resources died out. That is what happened on most of the Polynesian islands, including New Zealand.
Polynesia was settled by Austronesians who could herd, farm and engaged in long distance maritime travel and did so on purpose.
And I would guess much the same sort of people settled Madagascar. Around 1000 years ago Polynesians suddenly expanded beyond Tonga and Samoa, into what is now known as Eastern Polynesia. That was some 1000 years after they had first settled Tonga/Samoa. They had not been able to move east of that region until then. That could only have been achieved through a sudden improvement in boating. My guess is that it had been introduced from much further west, perhaps as far west as Indonesia. I would presume it was the expansion of the same technology that allowed a similar people to reach Madagascar from Indonesia at around the same time.
By the way, Polynesians did not actually 'herd'. They did carry pigs and poultry with them but both were basically allowed to roam freely.
The Polynesian population numbers reduced after several hundred years presence on each island even though they were able to move between islands. Other islands were already full and so they had nowhere else to go. On several smaller islands unable to support a sustained population humans became extinct.
My point is that the capabilities of Austronesians to impact a local ecology isn't a very meaningful way to determine the expected ecological impact of hunter-gatherers (apparently terrestrial hunter-gatherers) who may have arrived following an unplanned or ill planned one way trip.
I would have thought that raising chickens counted as herding in the sense of raising large groups of domesticated animals, although I can see the counterargument. I didn't recall one way or the other if the Austronesians had goats and/or sheep.
The hunter-gatherers of Australia managed to exterminate the megafauna. As did the first Native Americans. Hunter-gatherers are quite capable of huge ecological impacts. Even if an arrival was unplanned the population would increase exponentially if it had the genetic variation capable of surviving at all. Sooner or later the population would grow to large for the local ecology to support it. Then you have ecological change, which can be considerable.
The Austronesians did not carry any mammals with them except pigs, dogs and rats, all of which did considerable ecological damage. Neither pigs nor chickens reached New Zealand but the other two mammals managed to alter the ecology considerably, with human help of course. In Polynesia the chickens were not penned but are probably mainly responsible for the ecological replacement and extinction of megapodes through the islands.
Native Americans had dogs. Australia is the trickier point. Still, it doesn't boggle the mind to imagine that Melanesian mariners ca. 50kya may have been more culturally advanced or had larger bands that made them superior to African castaways ca. 4 kya in Madagascar who didn't exterminate megafauna.
The sense I get from the archaeological record reported in the 2013 study is that the first wave people of Madagascar persisted for many centuries, although perhaps not all of the way through to 500-900 CE when the Austronesians arrived.
Another possibility is that modern human hunter-gatherer superiority pre-food production was pretty much confined to open areas and thin forests, but not dense jungles. I think that the jungles of SE Asia are what kept modern humans at bay until Toba impaired the jungle opened the door for pre-Australians to make it to Melanesia. Madagascar was a real jungle in 2000 BCE too.
Or, perhaps the Madagascar modern humans didn't know how to make fire there. It was warm enough that they could survive without it (in terms of staying warm), and Australian megafauna extinction had a large component of wildfire utilization involved. A lack of fire also greatly impairs your ability to store food for lean times.
Some other reasons to think that dense forests were places where modern humans had little comparative advantage:
1. Lot of oral histories and myths about evil lurking in the dense forests, even in Europe.
2. Little or no mega fauna extinction in jungles of Africa or SE Asia.
3. Jungle populations tend towards the pygmy phenotype.
4. Early divergence of African jungle pygmies from other Africans genetically. Selective sweeps that removed paleo-Africans from most other areas didn't affect them nearly so strongly.
5. Jungles are home to almost all of the remaining uncontacted peoples in the world and those peoples do not appear to have much of an ecological impact there (e.g. Papuans, Amazonians).
"Melanesian mariners ca. 50kya may have been more culturally advanced or had larger bands that made them superior to African castaways ca. 4 kya in Madagascar who didn't exterminate megafauna".
That doesn't stand up to any real scrutiny. Melanesians certainly had a more advanced technology that did Australian Aborigines but they were later arrivals.
"Another possibility is that modern human hunter-gatherer superiority pre-food production was pretty much confined to open areas and thin forests, but not dense jungles".
I think that is absolutely correct. In fact humans only moved into heavily forested regions once the easily available resources in more open regions had run out. This is relevant to your next entry.
"perhaps the Madagascar modern humans didn't know how to make fire there. It was warm enough that they could survive without it (in terms of staying warm)"
The Tasmanian Aborigines lacked fire also, and it snows over much of Tasmania. And yet megafauna died out there too. Mind you, the Tasmanian Devil and wolf survived there until Europeans arrived.
"Melanesians certainly had a more advanced technology that did Australian Aborigines but they were later arrivals."
In the context I was using the term in, I was using Melanesians to refer to a group composed of Australian Aborigines and indigeneous Papuans, both ca. 50kya, not the current inhabitants of the region who have received genes and technology from the Austronesians.
In Tasmania, early on (no doubt when the mega fauna extinction happened) they had the same technology as the mainlanders and no doubt did have fire. They lost it only when Tasmania became an island and the population lost critical mass population size.
The Papuans of New Guinea and Melanesia look to be quite unlike the Australian Aborigines. The two have completely different haplotypes for a start. To me it is obvious that people arrived in New Guinea some time after humans had arrived in Australia (perhaps only a little after) and were basically a separate group genetically. As far as I know no-one has actually examined the difference although this map of differing mt-DNA's shows complete separation:
http://mtdnaatlas.blogspot.co.nz/2016/02/asia-has-five-mtdna-gene-pools.html
Humans did not move to the islands of Melanesia until some considerable time after humns had reached both Australia and New Guinea. Only the Melanesians and, to a much lesser extent, the New Guinea Natives, received such genetic input. The Aborigines may have received technological input as the microlithic technology seems to have been introduced to Australia about that time.
The population of Tasmania never fell bellow critical mass size (until Europeans began bumping them off). There were some 4000 individuals, quite enough to form a sustainable population.
Tasmania lost critical mass population size not because the number of people living in Tasmania fell, but because it was part of a much larger population with which it interacted and had genetic and cultural exchanges until it was isolated by water from the mainland. You can have a sustainable population at 4,000. But, you can't sustain the same level of civilization in terms of technology and cultural population with 4,000 people who are isolated as you can with 4,000 people who are part of a larger population of many hundreds of thousands of people.
New Guinea is also part of Melanesia in the sense that I was using it, so to distinguish between the two doesn't make sense. I think that the evidence strongly supports Papuans and Australian Aborigines arriving close in time to each other. Yes, the two populations do have genetic distinctions from each other, which could have arisen in several possible ways. But, it is not at all unreasonable to lump both as being part of the same basic wave of migration, although 45,000+ years of separation from each other has probably muted most of the cultural evidence of their once common origins.
"New Guinea is also part of Melanesia in the sense that I was using it, so to distinguish between the two doesn't make sense".
Yes, and no. Melanesia has a much higher proportion of mt-DNA B than does New Guinea. Mainland New Guinea has almost none whereas the proportion rises as you move east through Melanesia until it forms the huge majority on Polynesia. B cannot be older than about 6000 years in the region. The people in Melanesia and New Guinea are reasonably easily distinguished from each other as well. Although nowhere near as easily as can people from New Guinea and people from Australia.
"I think that the evidence strongly supports Papuans and Australian Aborigines arriving close in time to each other".
I don't think it does. The two regions have virtually non-overlapping haploid DNA and are easily distinguished from each other with the possible exception of people in northern Queensland. But it is widely accepted there has been an element relatively recently arrived there via the Torres Strait islands.
"But, it is not at all unreasonable to lump both as being part of the same basic wave of migration, although 45,000+ years of separation from each other has probably muted most of the cultural evidence of their once common origins".
I strongly suspect that Australia and New Guinea have never been connected by 'dry land' since humans first arrived in the region. The Arafura Sea was probably never more than very low-lying mangrove swamp, useless for hunter-gatherers. The routes to Australian also appear different for the two main Y-DNAs. C appears to have crossed near the southern end of Wallace's Line while K looks to have crossed via the Philippines and then south into Eastern Indonesia. Presumably the same holds for mt-DNA Ns and M respectively. And the Y-DNA K in Australia is definitely a subset of New Guinea Y-DNA K. It will be interesting when someone finally gets around to actually examining the genetic difference between the two populations.
I meant also to add that the distinctiveness of haplotypes is far more extreme between Australia and New Guinea than it is between East and West Eurasia. That is claimed to go back 30,000 years. And is even further differentiated than that between South Asia and both Southwest and Southeast Asia. Although we know that in both these cases there has had two-way movement in more recent times.
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