Malaria and Rome: A History of Malaria in Ancient Italy (33 page)

164

Demography of malaria

P. falciparum
does among children in tropical Africa today. The deviation in the English marsh parishes from the model pattern started at age 10, not 20, as in Grosseto, and steadily increased from the age of 30 onwards. Coale and Demeny Model West Level 6

gives a very good fit to English data up to the age of 20. However, Table 7 shows that this comparison is unsatisfactory from age 20

onwards.

Table 7. Number of people aged 20+ who die between ages x and y Interval

Marsh

West 6

West 2

West 1

parishes

20–9

18.3

14.1

19.1

20.7

20–39

36.8

28.8

37.7

40.4

20–49

58.6

44.1

53.5

56.7

20–59

75.9

61.2

69.9

73.0

20–69

87.4

80.3

87.0

89.1

Table 7 shows that from age 20 onwards the mortality rates predicted by Model West Level 6 are far too low. The attested rates of attrition are roughly consistent with Levels 1 and 2, with a life expectancy at birth of between 20 and 22.5, rather than 32.5 as in Level 6. In so far as the Coale–Demeny models are of any relevance at all, the English data indicate a drop from Level 6 mortality in the first ten years of life to a lower level from ages 10 to 20, followed by a sharp drop down to Level 1 or 2 from age 20 onwards.

Consequently life expectancy at birth in the English marsh parishes was probably rather lower than 33, the figure suggested by Level 6.

This would not be surprising in view of the exceedingly high crude death rates for the marsh parishes, up to 80 per 1,000. Nevertheless a more important conclusion, for the purposes of this chapter, is that when all the obvious environmental differences between the English marshlands and western central Italy are considered, the mortality patterns produced by
P. vivax
in England and the combination of
P. falciparum
and
P. vivax
in western central Italy were remarkably similar. Both were characterized by very excessive age-specific adult mortality relative to the prevailing levels of infant mortality.

Similarly Tognotti described deviations in the age-structure of mortality on Sardinia, which had some of the most intense malaria in the western Mediterranean. In Sardinia infant mortality in the Demography of malaria

165

first year of life was actually below the average of all the various regions of Italy (including regions where malaria did not occur at all).¹⁴³ In fact, infants in the first few months of life seem to be less severely affected by malaria than older infants. A variety of possible explanations have been offered for this phenomenon.¹⁴⁴ One possibility is that infants sleeping alongside their mothers have a much smaller surface area than their mothers, and move around more even when asleep, and so are less likely to attract mosquito bites.

Infants may also be carrying antimalarial antibodies derived from their mothers in the first few weeks after birth, although this may simply indicate a high transmission rate of malaria and have little effect on infections. Malarial parasites grow much more slowly in erythrocytes with foetal haemoglobin than in cells with the adult form of haemoglobin. Another possible explanation, noted in Chapter 5. 3 above, is that human breast milk contains an extremely low concentration of para-aminobenzoic acid, a chemical required by malaria parasites. These factors probably all interacted to reduce mortality and morbidity from malaria in very young infants on Sardinia. Nevertheless after the first year of life on Sardinia, the risk of mortality increased progressively until in the 10–15 age-group (normally the healthiest segment of any human population) mortality was higher in Sardinia than in any other part of Italy. The mortality regime as a whole of the human population of Sardinia was worse than that of any other region of Italy. The situation on Sardinia was fundamentally the same as in Grosseto and the English marshlands, namely that infant mortality was not a reliable guide to mortality levels in older age-groups. Human populations which are severely affected by either
P. falciparum
or P. vivax or both under the transmission rates and seasonality typical of temperate to subtropical climates exhibit distinctive and much more severe adult-mortality patterns which distinguish them from populations unaffected by any species of malaria. Demographic regimes in history characterized by excess adult mortality relative to infant mortality can also be produced by causes of death other than malaria. The recently published family reconstitution studies of English parishes have shown that until the eighteenth century the English population
as a whole
had adult mortality levels higher ¹⁴³ Tognotti (1996: 81–2 n. 11).

¹⁴⁴ Brabin
et al
. (1990); Riley
et al
. (2001) surveyed the possibilities.

166

Demography of malaria

than those predicted by the Coale–Demeny model life-tables for the prevailing levels of infant mortality:

Viewed in terms of the Princeton North or West model life-tables adult mortality was far too high relative to rates in infancy and childhood in the seventeenth century. If the only information available were the adult rates, and one were to extrapolate from them to estimates of expectation of life as a whole, using the Princeton tables, the result would be a radical underestimate of expectation of life at birth.¹⁴⁵

Nevertheless it must be remembered that mortality as a whole was lower in non-marsh parishes in England than in the marsh parishes ravaged by
P. vivax
. Malaria was the most powerful cause of these atypical patterns—atypical by modern, but not necessarily by pre-modern, standards. In the pre-modern world infectious diseases were vastly more important than they are today. The Coale–Demeny life-tables, which assume that decreasing levels of life expectancy at birth can be explained above all in terms of increasing levels of infant mortality, fail to pay enough attention to additional adult mortality caused by infectious diseases in historical populations. Similar patterns of excess adult mortality relative to infant mortality have also been observed in the historical demography of India. It has been suggested that tuberculosis was the most important cause of the atypicality in India, but malaria (especially P. vivax) has been very important historically in many parts of India.

Learmonth noted the striking correlations in Bengal until recently between, first, areas with intense malaria and areas with static or decreasing populations, and, secondly, districts with little or no malaria and districts with growing human populations. Malaria undoubtedly interacted with tuberculosis in India.¹⁴⁶ These atypical mortality patterns have had a wide geographical spread in recent times: England, Italy, India, and East Asia. It is a reasonable ¹⁴⁵ Wrigley
et al
. (1997: 349, cf. 261–3, 284–5).

¹⁴⁶ Mari Bhat (1989) on Indian demography, and Learmonth (1988: esp. 5–7, 206–7) on malaria in India. Even if the Sanskrit texts mentioned in Chapter 3 above do not definitely associate malaria with mosquitoes, other Sanskrit texts do describe malaria itself (a demon called
takmán
frequently found on lowlying land) very clearly, differentiating quotidian, tertian and quartan fevers: Zysk (1985: 34–44); Raina (1991: 1–4). Hirsch (1883: 204–7) described the distribution of malaria in India in the nineteenth century, and Klein (1972) its devastating effects in Bengal. Mari Bhat (1989: 110–11) also suggested, using the Barclay data, that the age-structure of mortality of traditional Chinese populations diverged from the model life-tables even more than that of Indian populations did, extending the patterns under discussion here even further.

Demography of malaria

167

hypothesis that they also have a long history. The balance of probability is that human populations that were affected by malaria in Latium and Tuscany in antiquity also shared these atypical patterns with high infant mortality but even higher adult mortality.

Modern quantitative knowledge of the extreme effects of malaria on human demography indicates that Toscanelli was right to suggest in 1927 that the spread of malaria from
c
.300  onwards did play a major role in the decline of the southern and coastal Etruscan cities, in exactly the same way that malaria led to the depopulation of the Pontine Marshes. From a methodological viewpoint, the conclusions reached here suggest that it is a mistake for ancient historians to assume that the model life-tables necessarily encompass the entire range of possibilities as far as the demography of human populations in antiquity is concerned.¹⁴⁷ It is now time to investigate the operation of some of the general principles which have been discussed so far in detail at the local level in the various environments of western central Italy. Let us start with the most notorious focus in Latium, the Pontine Marshes.

¹⁴⁷ The fact that extrapolations from data for adult mortality in historical populations often yield underestimates of life expectancy at birth is relevant not only to Roman demography, but also to the demography of classical Athens. Although this cannot be explored in detail here, it is worth noting in passing that the ratio between the ephebes and the arbitra-tors in Athens in the fourth century  (a measure of adult mortality), which has often been used to yield very low estimates of life expectancy at birth following comparisons with model life tables, probably underestimates
e0
, in the light of the present discussion. This provides further support for the view advocated by Sallares (1991: 113–14) that life expectancy
at birth in classical Athens has been underestimated. If infant and juvenile age-groups were in fact healthier in classical Athens than is generally supposed by historians, this helps to explain many important problems of Greek history; for example, how the Athenian citizen population was apparently able to recover very rapidly from repeated military catastrophes (as well as the ‘plague of Athens’ in 430 ) during the period of the fifth-century empire (cf. Sallares (1991: 95–9) ).

6

The Pontine Marshes

The Pontine Marshes have attracted little attention in modern historiography. The most comprehensive twentieth-century accounts of their ancient history were written by Bianchini, a rare book which attracted little attention owing to its publication at the beginning of the Second World War, and Hofmann, a very long Pauly-Wissowa article described by Brunt as ‘remarkable for its ready acceptance of annalistic details and lack of scientific data’.¹ Early modern descriptions of the region are very important.² In fact, virtually all the historical questions considered by twentieth-century historians had already been debated by writers in the eighteenth century. In the year 1800 Nicola Maria Nicolai published a very substantial work on the Pontine region consisting of four books.

The first two of these books provide an extremely detailed survey of the literary and documentary evidence for the history of the Pontine Marshes from antiquity onwards, as a prelude to a description of the bonifications of Pope Pius VI in the last two books. In view of the scarcity of twentieth-century literature on the subject, it is still well worth reading Nicolai’s books today. The main contribution of modern research has come from archaeology rather than history. Field surveys by Dutch and Italian archaeologists have recently added important new data. Collari described the history of bonification attempts in the Pontine Marshes.³

It is difficult to imagine now what the Pontine Marshes were like before Mussolini’s bonifications. Some parts of the marshes were permanently submerged, while other areas dried out in the summer each year. There were flooded forests in winter. In the early modern period, maize was planted in June and harvested in November in some parts of the Pontine Marshes which were submerged under water in winter.⁴ It was these seasonal, open marshes ¹ Bianchini (1939); Hofmann (1956); Brunt (1987: 349 n. 6).

²
e.g.
De Tournon (1831: i. 112–39, 319–21, ii. 213–37); Hare (1884: ii. 245–63).

³ Voorips
et al
. (1991); Attema (1993); Collari (1949).

⁴ De Felice (1965: 55–7, 108). D’Erme
et al
. (1984) shows numerous photographs of early modern paintings of the Pontine region.

Pontine Marshes

169

Veii

M O N T I

Tivoli

S I M B RU I N I

er Tiber

Riv

Bonifica di

Rome

Osteria dell’Osa

M O N T I P R E N E S T I N I

Maccarese

Praeneste

Ponte

Isola

Galena

Lago

Frascati

M O N T I E R N I C I

Sacra

Albano

C O L L I

Ostia

A L B A N I

Alatri

Castel Fusano

Albano

Nemi

Rocca

Massima

Velletri

Cori

M O

Frosinone

N T

Ardea

Norba

I

Cisterna

L

Ninfa

Norma

E PIN

T

Sermoneta

I

y

Po

Sezze

r

n

Latina

t

Amaseno

i

r

n e

Priverno

h

Anzio

M

Pontinia

e

a

M O N T I

Sonnino

r

AU S O N I

Astura

n

s h

N

e

i

s

Fondi

S E LVA D I

a

C I R C E O

n

Sabaudia