Some second thoughts:
A friend told me that Charles Darwin said he carried around a notebook in which he wrote down anything he learned that conflicted with his theory. Otherwise he might forget it the contrary evidence. It must have been a pretty empty notebook. I cannot imagine any real world evidence that would contradict the concept of evolution.
Aristotle said more or less, “Things happen by chance and what works persists.” No, I am not steeped in Aristotle in spite of having read him a lot. The quote appears in an introduction to Origin of Species by Darwin. I can’t come up with any potential real world evidence that would contradict Aristotle either.
Darwin said more or less, “Differential survival caused by inheritable variation will cause a secular inheritable change in a population.” If there is no secular change, then there can’t have been both differential survival and inheritable variation, so don’t expect to find any contradictory evidence. Indeed I can not remember any hint of contrary evidence in Origin.
What I say more or less is, “Nature will restrict the fertility of a large population because otherwise speciation effects will eventually drive a species to or close to extinction.” Show me a human population of ten thousand or more that survives random mating without recruiting for fifteen generations and I will be delighted; unless something I hadn’t thought of is going on, this would be a massive blow to my theory.
I do not intentionally ignore contrary data. But until now I had made no systematic evidence to collect it. But my friend’s implied advice seems good, and I now have such a notebook. Here are the explanations for two recent entries.
There is an article (Andre Lawler Uncovering Civilization’s Roots SCIENCE vol. 335 no. 6070 February 17, 2012 page 790) that describes recent archeology in Mesopotamia. It appears that a couple of the earliest regimes in that part of the world lasted longer than the data I used to chart their survival indicated. It also appears that they were not really highly developed urbanized societies with a privileged ruling class. So they should probably not be in the data set at all. This might shift a couple of points on my graph, but not by a lot. So the bottom line remains the same, but at least a part of the data is in question. I had always regarded that data with some suspicion. I didn’t get it from a professional source but from a souvenir wall chart. But having used it once, I was loathe to look around for a more respectable source, since I could then be accused of shopping for data that met my preconceptions. I shall not make any change for now, awaiting the day when a new timeline is complete and generally accepted.
Another article (Martin Medina-Elizaide and Eeico J. Rohling Collapse of Classic Maya Civilization Related to Modest Reduction in Precipitation SCIENCE vol. 335 no. 6021 February 24, 2012 page 956) described careful work sorting out just what the climate was doing during the decline of the ancient Mayans. There have been those who have shouted that it was only climate change that brought them down and those who said no, climate change had nothing to do with it.
Of course I took an interest. The Classical Maya also represent civilizations that I use as evidence. The current article says the climate change was real but modest and only one factor in an otherwise complex social change.
I’m good with that. There had been at least three phases, each marked by the kind of abrupt and durable change that makes me think that there was a population crisis with a new elite taking over. The fact that they were unable to put things back together after the last collapse may indeed be in part due to more difficult times, less rain, but that does not contradict evidence from earlier changes.
Of course climate change is trendy. There is an article (Felica A. Smith Some Like it Hot SCIENCE vol. 335 no. 6021 February 24, 2012 page 926 and Ross Secord et al. Evolution of the Earliest Horses Driven by Climate Change in the Paleocene-Eocene Thermal Maximum on page 959 of the same issue) describing horses getting smaller as things warmed up, just as one would expect. I would not be surprised to return a few centuries hence and discover that it was believed that our own civilization had been taken down by climate change. (All right, I would be totally surprised, but surprised by the return, not by what I found.) Any expert in the field would naturally look at our own literature and say, “Aha. They talk about climate change a lot, so that must have been the problem.” It would be sort of like looking at the fall of Rome and saying, “Cotemporary sources blamed it on moral degeneration, so that must be it,” even though in both cases I would hold demographics to be the driving cause.
So work on the Mayan is ongoing and of course what I have put together must be considered work in progress. But science is always work in progress so the company is not too bad.
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