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information.
    From this scatter, one could arrange many different sequences of fossils from older to younger, and suggest that this sequence might represent a probable evolutionary sequence between apelike ancestor and modern humanity. However, given the evidence at hand, you could link up more or less any sequence of fossils from this scatter and make other assertions of equal validity—without divine grace, who would know which was more likely to be correct?

    Figure 5
    In figure 6 I show three of the very large number of possible trajectories between ancestor (left) and human (right). All use the same scatter of fossils, but the trajectories are different from one another.
    The first is closest to the “truth,” but we could never “know” this. The three plots would, I think, have something in common and that’s this: the fossils used as links in the chain would, when arranged in the order the arranger assumes to be correct, show a progressive increase in those features assumed (retrospectively) to be characteristic of humans—more erect posture, larger brain, and so on. At no point would there be a reversal, such that a descendant would be more stooped than an ancestor, or have a smaller brain. Not that such things are not possible—the case of the Hobbit shows that they are—but because the assumption of progress is so ingrained that it would not occur to most people that there might be any other course besides onward and upward.
    Perhaps the most important thing to take away from this chapter is that new discoveries challenge our idea of progress—that matters are subject to a continual improvement, the refinement of each stage building on that of the one before in seamless progression. What the conceit of progress tends to ignore is the idea of loss—that many experiments in life were made that subsequently went extinct, and so are left out of the canonical tale of improvement.
    More than this, the idea of progress tends to be based on criteria that we decide after the fact according to our prejudices, and which need not be the most important or relevant ones. Because we seem to have larger brains and a more erect gait than earlier essays in the human condition, we always assume that the evolution of humanity is a story that must be told in terms of progressive increases in brain size and stature. This reasoning, however, is circular. We have larger brains than our presumed ancestors, so evolution must be couched in termsof brain size, so the discovery of creatures living in the past that had smaller brains will naturally confirm our prejudices. For all we know, our picture of human evolution might be better told in terms of, say, changes in the number of kinds of bacteria that live in our small intestines. After all, your body probably contains around ten times as many bacterial cells as human ones. 30

    Figure 6
    To really get a grip on why evolutionary arguments about human exceptionalism are wrong, you need to have a good understanding of what evolution is—and what it is
not
.
    The next chapters offer a handy cut-out-and-keep guide to evolution by natural selection. You might be surprised to learn that evolution by natural selection is far less—and far more—than you thought it was. After that I’ll discuss the concept of loss in more detail, showing how the stories on which we base our fragile suppositions about human exceptionalism are based on very little evidence at all.

2 :
All about Evolution
    The word “evolution” is probably one of the most abused words in any argument about science. To some, it is a rallying cry to rationality. To others, it’s a term of abuse, the term “evolutionist” hardly less derogatory than “abortionist.” There can be few other words that get so much mileage while remaining so poorly understood. “When
I
use a word,” said Humpty Dumpty in Lewis Carroll’s
Through the Looking-Glass
, “it means just what I choose it to mean—neither more nor less.”