Sunday, October 04, 2009

Climate change cuts both ways

Jared Diamond surveys the impact of climate change research on three roughly contemporaneous civilizations in the most recent issue of Nature (subscription needed): Maya, Khmer, and Inca. The first two might have declined because of environmental changes, but the Incas, who built their empire in high altitudes, benefited from it. We are talking of the period between the 9th and 12th centuries CE. Excerpts:
From time to time, separate archaeological projects on different societies end up by suggesting common themes to events in the ancient world. Thus, two new studies point to parallels between the collapse of cities on opposite sides of the globe — the southern lowland Maya cities in Central America, and Angkor, the centre of the Khmer empire in what is now Cambodia. These parallels include the effects of climate change, which hurt both the Maya and the Khmer. By contrast, as a third report indicates, climate change seems to have benefited another ancient civilization, the Incas of South America.


This reminds us that climate can change in either direction, and that in the past such change has variously helped or hurt human societies. But human overexploitation of environmental resources never helps. As Lentz and Hockaday note, "Tikal's inhabitants became trapped in a positive feedback loop wherein increasing demands on a shrinking resource base ultimately exceeded the carrying capacity of their immediate environs. The ecological lessons learned from the Late Classic Maya, with their meteoric population increase accompanied by environmental overstretch, serve as a distant mirror for our own cultural trajectory." Amen.
The same Nature issue also has articles on the genetic history of Indians -- a loaded issue, no doubt. For an abstract of the study, see here.

I'll try to avoid subscription only links in the future -- my apologies to readers.


Alex Engwete said...

Does the article say whether these changes occurred by the act of some kind of a deus ex machina or by the action of men ? Years back I read somewhere that the kingdom of Nubia disappeared due to the massive deforestation caused by the residents to feed their giant furnaces...
I also read the abstract of the genetic history of India. Disturbing indeed to the lay person I am, as the authors “predict that there will be an excess of recessive diseases in India.” What are “recessive diseases”? Well, maybe I need to “google” that one…

Krishnan said...

Hari, have you read Jared Diamond's Collapse ? I am yet to get hold of this book. I was enlightened by his other 2 books - The Third Chimpanzee and Guns, Germs and Steel - easily most important books IMHO.

Hari said...

Alex -- The general argument is that overexploitation by both Maya and Khmer caused a slow, protracted decline in both societies. No specific personalities are mentioned. There's some scientific analysis of materials from that time (beams from buildings were sampled, for instance, as were mud cores).

Recessive diseases, it appears (I googled too!), are genetic diseases, where both parents transmit the same bad gene. This might happen after centuries or millennia of marrying within the same community -- that is the norm in India, actually.

Krishnan -- I have not read Collapse. I attended Diamond's talk about it, and decided it is not as good as Guns, Germs and Steel, which is a stunning book -- it completely changed my view of the world. In fact, even today I am heavily influenced by what I read in GGS; and much of my writing on Native American history is informed by it.