100 YEARS AGO

What mutation is in biology, conversion is in psychology, and revolution in sociology. It may be said that to assume such parallels is merely to beg the question, but I think that the apparent parallelism cannot be without significance... If the supposed analogy is a valid one, it appears to follow that mutability is due to the same general causes as ordinary variability (just as change of opinion and reform are due to the same general causes as conversion and revolution), but that there is this difference — mutability represents an explosion of energy, as it were, in a given direction, and therefore differs from ordinary variation somewhat as the firing of a gun differs from the explosion of a loose heap of powder... [T]he chance of mutations succeeding from the first is comparatively remote, though such a thing is quite possible; but since they are the result of general causes, the sort of changes the mutations exhibit are likely to come about in due course, just as the sort of changes represented by a revolution are likely to prevail ultimately, though the revolution itself may appear to fail.

T. D. A. Cockerell

From Nature 16 February 1905.

50 YEARS AGO

Amazon Head-Hunters. By Lewis Cotlow. The author of this book is a New York insurance broker whose hobby is travelling in lands inhabited by primitive races... Between 1940 and 1949 he made several expeditions to the north-west of the South American continent... These are the areas inhabited by the Choco, Colorado and Yagua Indians, and include also the very isolated country of the Jivaro Indians, who are especially known for their custom of drying and shrinking the heads of their enemies... Mr. Cotlow was able to become very friendly with several of their chiefs, and they informed him of the number of heads which they had taken during their lives. He brings out forcibly the fact that the relatives of a man slain in battle are in honour bound to kill his killer and to shrink his decapitated head. The relatives of this victim must retaliate in the same manner, so that inter-community warfare is almost continuous. The author describes fully the method of shrinking a head. Unfortunately, he did not actually see it carried out, since at the time of the raid he was stricken with dysentery.

From Nature 19 February 1955.