The Existential Equation – The Irish Pre-famine Population and the Dilemmas of a 7 billion person world

by Liam Heneghan

The Irish Famine of 1846 killed more the 1,000,000 people, but it killed poor devils only. —Karl Marx, Capital Volume 1 (1867)

Behold the potato chip! It’s the perfect substrate for immersing in delicious oils, an adroit vehicle for conveying toothsome flavors to the mouth. If one eschews the oils and the suspicious flavorings, the potato is almost a complete meal in itself. Mashed along with a little buttermilk it fueled, as is claimed with some hyperbole of course, the construction of a British empire. Viewed with a squint, it is as if the Irishman with spade in hand was the subterraneFamine0001_4an potato tuber’s extended phenotype – another starchy being anxiously grubbing back into the dirt. Hundreds of thousands of potato-fed and buttery Irishmen left for Britain during the 19th Century to find employment as navvies and there they dug ditches, canals, and built a railroad system. And during and after the Great Potato Famine (1845-1849) millions more left for North America and elsewhere.

For me this is personal. Because of the enormous productivity of potato – an acre of potato producing more calories than thrice that of grain – I am now living in the US. I am, if my assessment is correct, the very last of the post-potato-famine migrant from Ireland. As soon as I left (in 1994), the exiles commenced their return, and though migration out of Ireland has begun again it is no longer, it seems to me, the same demographic pattern initiated by the failure of the potato crop.

My principle concern here is not the potato nor the Irishman nor the empire: I am interested in revisiting the demographic implications of events surrounding the Irish Potato Famine; examining the way in which economic and social historians have assessed the population growth running up to the famine before the horrible consequences of the potato failure unfolded. Let me make my main point here: nothing could be seemingly simpler to come to grips with than the pattern of a population growth in the century leading to Irish famine, and the increasing reliance of the poor on a single crop and the subsequent crash of the population after the failure of the crop. And yet despite the beguiling but horrifying simplicity of the pattern almost no aspect of the story is as easy to explain as it may seem. To keep this post to modest length I am discussing only the debates over causes of population growth before the famine here and will post follow up comments on my blog in the coming months about the population disaster that followed the potato failure – another complicated story.

Before assessing the pre-famine population patterns a word or two on the potato itself. The potato (Solanum tuberosum) is an annual herbaceous dicotyledonous plant that produces a carbohydrate- and protein-rich edible tuber (underground storage stem). As an annuals herb, the potato has much in common with several weedy species. The plant is a member of the family Solanaceae and thus is related to several other cultivated plants: tomatoes and peppers, for instance. Indeed, an Irish person outside a pub with a potato chip (or “crisp” as it is called in Ireland) in one hand, and a cigarette in the other is enjoying the dubious benefits of two members of the Solanaceae. Potatoes were first domesticated in highlands of Bolivia and Peru and were introduced into Europe by Spanish explorers in the late sixteenth century. The potato made the return journey to the New World from Europe in 1791 being supposedly introduced to the US from Ireland.

The climatic conditions that make Ireland a slight misery to live in permit potatoes to thrive – cool temperatures, overcast skies and perpetually moist soils are ideal for the crop.

The potato follows rice, wheat, and corn, in supplying calories to the human population. Besides being scrumptious, a potato supplies a good balance of the essential amino acids. They also are a source of B vitamins and vitamin D and C.[1] Potato also contains a host of micronutrients, most of which are found closely below the skin – I encouraged you all to eat your spuds Famine0001_6with their jackets on. If you peel them the skins can be fed to the pig that you might be fattening up to sell for rent (or at least in pre-famine Ireland this would be the recommendation and was the standard practice). The high productivity of potatoes in tiny land-spaces contributed to its rapid adoption as part of the Irish agricultural practice and diet. At a time of rising populations the potato was the perfect crop – the higher the population the greater the dependence on the potato and the potato in turn facilitated a further rise in population. Both species contributed to each other’s success. And the collapse of one lead to the collapse of the other.

There is little in dispute about the proximate cause of the Irish post-famine population decline – the almost exclusive dependence of a relatively vast Irish population on a single crop whose failure resulted in starvation, death, and emigration of the Irish. Beyond these horrifying and indisputable generalizations there is little agreement on other issues associated with the Great Famine. The exact contribution of flawed land policy and landlordism in the run up to the famine, the degree to which the political response contributed to the exacerbating or relief the famine, even, to some extent, the estimates of death (ranging from half a million to well over 1 million), are all still contentiously debated. The rise of the Irish population before the Great Famine, the main concern of this little piece, has also attracted some scholarly attention, and though the pattern seems comparatively straightforward, the theories explaining the demographic situation are also contentious.

So, the population of Ireland in the year 1800 was 3.8 million. The data is not completely reliable, but the patterns are very clear. At the eve of the famine it had risen to incredible 8.1 million! The accompanying graph, based upon the census returns of 1821, ’31 and ’41 illustrates just how rapid this was (I reconstructed these based upon the census returns for Ireland that can be found at Irish growth rates were in fact the highest in Europe at the time, though just before the famine the growth rates seemed to have declined to 0.9% per annum. [2] It was as if the population bow had been drawn to its limits and the arrow of disaster was poised for release. Irish Population 1821-1911

This rapid period of population growth was not just an Irish phenomenon, it had occurred throughout Europe though at comparatively slower rates. To represent such growth mathematically requires little in the way of computational finesse: populations grow when birth rates exceed death rates. Despite the delicious tractability of the basic population model, after all it can be expressed as ∆P=B-D (change in population = births – deaths), the genius of the human is to transform the simple factors B and D into everything that gives our lives meaning. All that’s beautiful and terrifying is embedded in this most existential of equations. Population grows when any combination of events result in birth being more prevalent than death; so even if mortality rates increase as long as more kids are born into the misery, populations continue to grow.

So what was going on it Europe in the 18th and 19th centuries that resulted in rapid population increases? This period of rapid growth, though it was not the first period of growth in human population history, is significant in being the one that marked a beginning of the modern population spurt whose outcome is today’s global population. Between the end of the 18th century when the global population was 1 billion and today the world’s population ballooned to 7 billion. The most plausible hypothesis concerning the origins of this contemporary growth spasm is that during the period mortality rates declined, and though in some cases birth rates also declined mortality rates, crucially, declined at a faster rate that the birth rate decline. This difference between mortality and fertility opened a “gap” between births and deaths and the population as a consequence increased. To be clear, postponing death, which is inarguably happy news, has consequences.

The reduced prevalence of infectious diseases was a main contributor to the decline in mortality. Contributing to the decline in infectious diseases were improved diets, sanitary reform and an altered relation between infectious agents and the human host.[3] Many demographers are adamant that the declining mortality during this period was not related to medical genius. Medical knowledge at the time did not extend to comprehensive knowledge of major infections killers of the day. There is evidence for a spontaneous decline in some of the historical mass killers – scarlet fever, for instance – but this is not enough to explain the sharp decline of mortality.

The evidence of a role for improved nutrition in contributing to mortality decline is solidly founded. The better fed and healthier European of the 19th century derived their good fortune from newly emerged agricultural technologies, ones based upon better conservation of soil fertility and more sophisticated ecological knowledge of crops diversity. The diversification of crops was important – besides averting the sort of disaster awaiting Ireland in the 1840s, new crops in Europe ensured a reliable supply of food year round. The potato was the absolute king of the root crops, but turnips, beets, carrots and parsnips were planted. These roots also provide feed from livestock in the winter, increasing the amount of meat available for consumption or sale. It seems a little obvious to underscore it, but improved food quality and greater availability of calories are crucial to sustaining a population – and even if these factors don’t inexorably lead to population growth, they are necessary for it. More positively, the role of food quality and availability on reduced mortality rates contributes to population growth as long as birth rates are relatively unaffected.

Now, speculation about the factors contributing to the growth of populations during the 18th century were developed primarily through a detailed examination of the records of births and deaths in England and Wales, but do the patterns hold for the remainder of Europe? Peter Razzell, a noted population historian, remarked that the Irish population lagged for almost a century after the potato became a commonplace crop in that country and thus cautions us not to expect the generalizations to hold true outside of Britain. The case that something quite different was going on in Ireland from a population perspective was systematically made by Professor Ken Connell, a professor at Queen’s University Belfast, over 60 years ago. [4] Life in Ireland was so different from Britain that surely it could not be generated by the same demographic mechanisms. Since in Ireland several of the factors that reduced mortality in Britain may not apply, Connell argued that Ireland’s population grew by the only other way populations can – increased fertility. Prior to the 19th Century marriage was postponed until the death of the father by which time “the son was no longer a stripling” – thus later marriages were the norm. As the population grew in Britain, the incentive for Irish farmers to provide food for British market grew, and this along with other more local Irish factors provided an incentive for the further subdivision of land holdings, which did indeed become more prevalent. All of this was fueled by the productivity of the potato! A postage-stamp sized farm worked by a manling, his child-bride, and their growing brood could be sustained by potatoes. Since they were married longer, Irish women were exposed for a longer period to childbirth – though the evidence is equivocal on whether this did in fact translate into higher fertility among Irish women.

From this perspective the potato’s main crop was that of healthy cheap labour, and this inexpensively produced Irish laborer allowed landlords to subdivide their properties and maximize their rents.

Professor Connell’s case for Irish exceptionalism seems less secure these days than it did back when he was writing. Connell had been a pioneer of Irish social and economic history and chaired his department at Queen's for a while. A querulous sort, apparently he did not get along well with his colleagues and was removed from his leadership role. He died on 26 September 1973, aged fifty-six, embroiled in a number of controversies and “exhausted and dispirited”.[5] Michael Drake’s paper, Marriage and Population Growth in Ireland, 1750-1845, published in 1963, challenged the statistical basis of Connell’s account, and though subsequently Connell’s thesis remained frequently cited by other scholars it was often to caution against or at the very least comolicate his conclusion. [6] In 1974 Drake wrote an obituary for Connell who died the year before at age 56 in which he praised him for writing “the first major study of the determinants of population growth in pre-industrial societies to emerge since the 1920s”, and credited him with initiating a much closer scrutiny of this phenomenon. The major criticism he said was that Connell “generalised too widely”. Drake concluded on this sad note: “Certainly in all the years I knew him he budged but little on any issue. Perhaps if he could have done so on those often seemingly trivial non-academic issues which troubled him so much, especially in recent years, he would be with us still.” On a cheerier note Joel Mokyr of Northwestern University (whose office is a few blocks from where I write) and Cormac Ó Gráda from University College Dublin (whose office was a few buildings away from the lab where I worked in the late 1980s) concluded a more recent review of populations with the comment: “Post-famine demographic patterns have fascinated and puzzled researchers too, but it must be said that as yet they have not produced a Connell. As for the period surveyed here, three decades of debate have not exhausted the questions raised by Connell.”

In more recent analysis the point is conceded that despite anecdotal evidence to the contrary the age of marriage in Ireland was not impressively early in Ireland and was closer to the norm for Europe. There is, however, some evidence that marital fertility was greater in Ireland than in Britain. Though there is little hard data to base it upon, the Irish seemed not to have inclined towards the use of any contraceptive strategies even when they knew about them. Charmingly, Irish women of that time were complemented for their chastity and marital fidelity. [7] To add to the growing thicket of factors contributing to the rapid growth of the Irish population before the famine Jona Schellekens, from Hebrew University of Jerusalem, suggested that marital fertility may have been caused by improved nutrition but also by changes in “the pattern of breastfeeding linked with potato cultivation provide a plausible hypothesis.” [8]


Can the Irish Great Famine be used as a microcosm for contemplating the potential fate of the world’s population as it surges past 7 billion in the months ahead? After all, as was true in Ireland before the famine, the world has run up its populations impressively since the early 1800s and will a mere couple of centuries later reach 7 billion this autumn. Are we heading, as many environmental thinkers have implied, for a collapse? Was Ireland's famine a predicable Malthusian disaster as some have claimed – a case of a population outstripping its resources? I leave these as open questions for now as I suspect in the months ahead we will be encouraged to reflect upon them. There is a cottage industry of speculation about the degree to which the Irish situation was a Malthusian disaster (I’ll review some of this on my blog). For now, all I want to say in this: Despite the seeming tractability of population issues (growth = births – deaths), it is pretty clear that dissecting the particulars of any one story – in this instance, the simple pattern of population growth on a small damp island before a major famine – it is rarely possible to fully understand the mechanisms driving the pattern. This is precisely because growth models embed such existential matters; motivations lofty and iniquitous, deliberate and capricious, contribute to the births and deaths of humans. And we are a long way from understanding the human condition, or its reflection in the patterns of our births and deaths.

A final thought: Quite a few years ago I invited some close friends over to watch Jude, Michael Winterbottom’s version of Hardy’s novel Jude the Obscure. I had read the book with enormous relish as a teenager in Dublin and had remembered it for its compelling tale of Jude’s desire to be a classics scholar, thinking it in some ways to reflect my own situation. I urged this tale of scholarly ambition on some dear friends. In my callowness I had forgotten a central scene where Jude’s disturbed son murders Sue’s (Jude’s beloved) two children and then hangs himself. The note he leaves for Jude read, “Done because we are too menny” [sic]. As this horrifying scene unfolded on the TV one of our guests started to quietly sob and after a while her husband was obliged to carry his inconsolable wife off to their car. All I could say in pitiable defense was that I had forgotten.

Not to be too melodramatic, but in the months ahead when the now staggering size of the global population is discussed, and we are again invited to contemplate if we are globally too “menny”, recall that though populations are stabilizing in some regions, they are not in other generally poorer countries, and that the patterns of population growth and decline are only approximately well understood. We tend not to be very good at projecting the numbers out too far into the future. Those who fear that the population bow is being pulled globally tight and that disaster is being drawn from the quiver (and starvation is not the only arrow) should not be mollified by confident-sounding predictions that population stabilization is in our near future – perhaps it is, perhaps it is not, we simply cannot be sure. The only thing that seems sure is that if populations stability is deemed desirable we must, to paraphrase population theorist Joel Cohen, be “ready, willing, and able” to determine our own fertility. An expectation that the existential equation ∆P=B-D will crank out uncomplicated results is historically poorly grounded.

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Photos in this column are by Liam Heneghan

[1] J. Creighton Miller, Jr., H. David Thurston, “Potato, Irish,” in AccessScience, ©McGraw-Hill Companies, 2008,

[2] Joel Mokyr and Cormac Ó Gráda (1984) New Developments in Irish Population History, 1700-1850 The Economic History Review, New Series, Vol. 37, No. 4, pp. 473-488

[3] Thomas McKeown, R. G. Brown and R. G. Record (1972) An Interpretation of the Modern Rise of Population in Europe. Population Studies Vol. 26, No. 345-382.

[4] K. H. Connell (1951) Some Unsettled Problems in English and Irish Population History, 1750-1845 Irish Historical Studies Vol. 7(28): 225-234

[5] C. J. Woods. (2009)”Connell, Kenneth Hugh”. Dictionary of Irish Biography. (Eds.)James Mcguire, James Quinn. Cambridge, United Kingdom:Cambridge University Press.

[6] Michael Drake (1963) Marriage and Population Growth in Ireland, 1750-1845 The Economic History Review Vol. 16, No. 2 (1963), pp. 301-313

[7] See Joel Mokyr and Cormac Ó Gráda for details/

[8] Jona Schellekens (1995) The Role of Marital Fertility in Irish Population History, 1750-1840. The Economic History Review, New Series, Vol. 46, No. 2 (May, 1993), pp. 369-378, p377