an autodidact meets a dilettante…

‘Rise above yourself and grasp the world’ Archimedes – attribution

Posts Tagged ‘climate

a bonobo world? 4

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a group of Rapa Nui people, photographed in 1895

Chapter 1 – Culture (continued)

It isn’t known precisely when the Polynesians first settled on Rapa Nui, but there appears to have been regular habitation there from about 800 years ago. It’s clear from the numerous moai – we know of at least 900 – carved by the Rapa Nui people, and the great platforms, or ahu, upon which they were displayed, that they had developed a sophisticated, creative culture during the first few centuries after their arrival (building upon eastern Polynesian traditions found on other islands), but it seems this was very much in decline by the time of Roggeveen’s 1722 visit. It’s the causes of this decline that are very much the subject of modern debate.

Rapa Nui is a volcanic island, and was thickly forested in earlier times, as researchers have found through paleobotanical analysis. However, by the early eighteenth century, almost all of the trees were gone. The controversy revolves around whether and how much the Rapa Nui people engaged in self-destructive behaviour, in relation to their natural resources, resulting in population collapse. According to Deutsch, following Bronowski, the self-destructive behaviour of the natives was a counter-example to the ‘ascent of man’ or ‘the beginning of infinity’ that Deutsch admires in the form of the short-lived but brilliant ancient Athenian culture, and in modern scientific humanity. However, I feel that both Deutsch and Bronowski have over-simplified and thus seriously distorted Rapa Nui culture to make their case, and that these kinds of distortions can be generalised to show that many of us still treat other cultures in a dismissive and hubristic way, when a more open and sympathetic understanding can only improve our own culture, at a time when, arguably, our future isn’t quite as rosy as we would like it to be.   

In his account of the Rapa Nui cultural collapse – which certainly did occur – Jared Diamond is more sympathetic. With the help of scientific associates, he examined a number of variables affecting deforestation on Pacific islands. They found that deforestation is more severe on: 1) dry islands than wet islands, 2) cold high-latitude islands than warm equatorial islands, 3) old volcanic islands than young volcanic islands, 4) islands without aerial ash fallout than islands with it, 5) islands further from Central Asia’s dust plume, 6) islands without makatea (coral reef rock) than islands with it, 7) low islands than high islands, 8) remote islands than islands with near neighbours, and 9) small islands than big islands

Collapse, Jared Diamond, p116

Based on these criteria, and his finding that Rapa Nui ticked 8 out of 9 of the above boxes, Diamond came to this judgment:

In short, the reason for Easter’s unusually severe degree of deforestation isn’t that those seemingly nice people really were unusually bad or improvident. Instead, they had the misfortune to be living in one of the most fragile environments, at the highest risk for deforestation, of any Pacific people. For Easter Island, more than for or any other society discussed … we can specify in detail the factors underlying environmental fragility.

Of course, questions remain, Such as: Why would a culture destroy a resource (its trees) when it relied on that resource so heavily? How, exactly, was that resource destroyed? Was it actually the result of human activity, and if so, what kind of activity? And there are other questions about the Rapa Nui population itself. It seems to have imploded in the period between the building of ahu and moai, and the incursions of Europeans in the eighteenth century. However, there’s much disagreement about the population of Rapa Nui at its height, with some claiming it may have been as much as 15,000 – a large number for such a tiny island, when the inhabitants had to depend entirely on that island’s resources. But these numbers are very rubbery, as is the length of time that these Polynesian adventurers had been inhabiting the island – anywhere from 800 to 2700 years. I am reminded of similar uncertainties and debates about Australia’s first inhabitants; dates range from 45,000 to 80,000 years, and the populations are anybody’s guess, but that doesn’t stop researchers from guessing. Surely there would have been wide fluctuations in the populations over time, as the climate warmed and cooled. In any case, the Rapa Nui population was supposedly reduced to approximately 3000 by 1722, though how this figure was arrived at is a mystery. Clearly Roggeveen didn’t take a count, and the Rapa Nui people were not in a position to keep written records. Unfortunately everything about this island’s pre-European history is subject to ongoing debate.

Evidence clearly shows that some 21 species of trees and the island’s land birds had disappeared by the time of Roggeveen’s visit. The rats brought to the island may have been the cause of much but certainly not all of the plant devastation, and the loss of many of the biggest trees may have affected the inhabitants’ ability to build canoes for fishing expeditions. Research has shown that the Rapa Nui people’s diet contained far less fish and seafood than that of other Polynesian Islanders. However, claims by Diamond and others, of a breakdown within the culture leading to internecine warfare and even cannibalism, have been controversial. The obsidian blades found on the island may have been fashioned for farming rather than fighting. More importantly, for my own thesis of the superiority of co-operative societies, (bonobos as opposed to chimps), recent research seems to be converging on a view that contradicts Diamond’s story of increasing competition in the form of ever more monumental statue building in a heavily hierarchical society. We may never know for sure, but anthropologist Carl Lipo had this to say on the research in 2018:

Lipo explained that there is no archaeological evidence for the control of resources or any hierarchical distribution of resources, which is leading to a new narrative about the pre-contact Rapa Nui society: that the island was not dominated by massive chiefdoms, and rather, communities shared resources without any prehistoric warfare.

I cannot of course vouch for the truth of this new interpretation of Rapa Nui culture, despite hoping that it’s more accurate. What is definitely true and uncontroversial is that the arrival of Europeans, and the diseases they brought with them, was far more devastating for the Rapa Nui people – as well as Australia’s Aborigines – than anything they ever did to themselves. 

References

Collapse, Jared Diamond 2005

The beginning of infinity, by David Deutsch, 2011

https://en.wikipedia.org/wiki/Easter_Island

https://en.wikipedia.org/wiki/History_of_Indigenous_Australians#:~:text=A%20cumulative%20population%20of%201.6,currently%20the%20most%20heavily%20populated.

https://www.eurekalert.org/pub_releases/2020-02/bu-eis020620.php

Written by stewart henderson

October 28, 2020 at 11:21 pm

on dinosaurs and the Cretaceous climate

with 2 comments

sauropods of the Jurassic and Cretaceous – they munched on superfoods, apparently

 

I’ve been reading this entertaining book on dinosaurs by the curmudgeonly controversialist Brian Ford, who insists that dinosaurs were largely aquatic. I know about as much about dinosaurs as Trump knows about government, so I’m not going to wade into the central debate, if there is one (most palaeontologists dismiss Ford’s claim out of hand), but there’s so many items and assertions here worthy of further investigation that I’m bewildered by choice. So I’ve decided that, since there’s so much interest in current climate change and what it might mean for the future of various biosphere life-forms including ourselves, I’ll spend a bit of time researching what’s known about the climate, and the atmosphere, during the Cretaceous period – a very long time-span indeed from a human perspective, stretching from around 145 million years ago to 66 million years ago. It seems to have have been very different then (assuming that 80 million years of weather can be encapsulated in one description) from what it is now, and yet life was thriving – so why worry?

Well, life then was life as we don’t know it now – though, interestingly, many plants of the period still exist today, including plants from even earlier, such as gingkos and horsetails. In fact, the Cretaceous saw the emergence of flowering plants (angiosperms) in great numbers, and this favoured a rise in dinosaur numbers and types. The climate generally was warm, wet and tropical, and according to NASA climate scientists, carbon dioxide levels were at 1000 ppm (in the middle Cretaceous, around 110 mya), compared to around 410 ppm today. Sea levels were around 300 feet higher than today, and surface temperatures averaged 27 degrees celsius compared to about 15 at present. It’s likely that no ice existed anywhere on the planet.

So why so much CO2, and how did it come to drop? To take the second question first, at this time, the continents weren’t where they are today. Some 90 mya India began a rapid movement away from Madagascar towards Asia at a rate of 15-20 cms per year. It collided with the Asian plate some 55-50 mya, creating the Himalayas, and silicate weathering began, resulting in the incorporation of CO2 into carbonate, which washed into the ocean and was buried. The surface temperature started to drop with CO2 levels, which came down to an inter-glacial atmospheric concentration of about 280 ppm in CO2. Once that concentration got down to 450 ppm the Antarctic ice sheet began to form, and the Greenland ice sheet started at around 400pm, all of which is highly relevant to today’s climate situation with its rise in CO2 levels.

As to the first question, plate tectonics and related volcanic emissions appears to provide most of the answers. It’s believed, in fact, that CO2 levels were as high as 4000 ppm during the Cambrian period, over 500 mya (and at their lowest at 180 ppm during the Pleistocene glaciation a little over 2 mya).

None of this, of course, comes close to answering questions about dinosaur lifestyle, but I do note that Brian Ford is an outlier not only for his aquatic dinosaur hypothesis. He also questions, indeed trashes, the dinosaur extinction-by-meteor story, and argues that the sky was probably orange-yellow, to our perception, at the time of the dinosaurs. All of this is contrary to generally accepted science, so he’s rather unlikely to be correct. Having said that, questions about how some of these incredibly massive sauropod beasties managed to get around and consume enough food to maintain themselves – these still appear to be unanswered to a large degree. Hopefully somebody will build a time machine soon.

References

Too big to walk, by Brian Ford, 2018

https://www.livescience.com/44330-jurassic-dinosaur-carbon-dioxide.html

PSW 2404 Satellites, Dinosaurs, Milankovitch Cycles, and Cretaceous Earth | Compton Tucker (video)

What was the climate like during the age of Dinosaurs? / Benjamin Burger (video)

https://ask.metafilter.com/194137/What-color-was-the-sky-millions-or-billions-of-years-ago

https://www.sciencemag.org/news/2019/10/sauropods-grew-big-munching-superfoods-sturdy-beaks

Written by stewart henderson

December 11, 2019 at 12:53 pm