Bad lands and swollen glands

Despite concerns about new and emergent diseases, most of us live safely cocooned from the biological realities faced by our ancestors. One of the tasks of historians, demographers and epidemiologists is to recreate that savage world for us, giving us a glimpse of the untold slaughter carried out by disease organisms through the centuries.

Susan Scott and Christopher Duncan examine in exhaustive detail many of the pressures that were responsible for this winnowing-out of our ancestors. They concentrate on parish registers and other historical records in England, focusing on the two and a half centuries from about 1550 to the beginning of the 19th century. Much can be gleaned from these records, but the book leaves larger questions unexplored.

The text mainly examines birth and death records in Penrith and its surrounding communities in the north of England. Until the arrival of the railways, these towns and villages were isolated - "inaccessible to travellers andI regarded with repulsion by outsiders". Agriculture was primitive, with astonishingly low yields, so it is unsurprising that disease and malnutrition were rife, and birth rates in Penrith were much lower than in other areas.

The plague (or what was suspected to be the plague) hit Penrith in 1554 and 1598, and its impact was felt for a century and a half afterwards. Plague might have been the trigger of population fluctuations, but it is possible that it spread when the population reached its carrying capacity - an effect of fluctuation rather than a cause. But the authors fail to explore such distinctions in detail.

They find that many other fluctuations in births and deaths had at least some correlation with a grim litany of now half-forgotten diseases - smallpox, scarlet fever, whooping cough. The fluctuations vary from one disease to another, perhaps reflecting their underlying biology. There is no doubt that some of the illnesses, particularly smallpox, had clear periodic impacts on the afflicted populations, but I suspect that many of the fluctuations seen in the less lethal diseases are a product of statistical noise. Unrecorded, and therefore unexamined, were the diarrhoeal diseases that probably accounted for most infant deaths and pneumonia that carried off young and old.

The book provides a valuable analysis of the impact of economics on the populations in England. Particularly striking is the fact that mortality rose and birth rates fell at Penrith when wool and grain prices were low, while the reverse seems to have been true for the market town of York. What was tough on the farmers, it seems, was good for the middlemen.

Scott and Duncan offer a fascinating glimpse of the impact of disease on our ancestors that will be of interest to demographers and epidemiologists. But it would have been far more interesting for the general reader if the numerous graphs and charts had been supplemented by more of the human story.

Christopher Wills is professor of biology, University of California, San Diego.