Calculation of the European population in the 5th century

The basic rule is that the population in the 5th century AD was some 10% of the modern one. In fact the European population hardly changed over the ages until the 19th century. This figure must be adjusted according to the fertility of the land and the climate. For southern Europe we must increase the figures, for northern Europe we must decrease the figures.

France has today some 65 million inhabitants. In AD 428 the population would be 6.5 million. But as Gaul or France always was a fertile land with a heavenly climate, we must increase this figure, 8 million is more realistic. Denmark has today some 5.5 million inhabitants, 10% = 550 000, but as the climate is cold and wet some 300 000 people is closer to reality, maybe less.

We must take in account a number of criteria:
(1) The staple crops were of Mediterranean origin. This means that the wheat varieties were not yet acclimatized (or selected for) to northern climate conditions. Even today, this acclimatization is not complete. At the time, a bad summer in northern Europe meant a considerable drop in production, if not famine.
(2) Farmers used a system of production spread over 3 years on the same land. The first year the most valuable but also the most demanding crops were planted, like wheat. The second year, less demanding crops were planted, like some vegetables. The third year, the land rested. At the end of the third season, what ever grew on the parcel was burnt. The ashes fertilized the land and the next year exploitation could start all over again. This system meant that 3 times more land was needed to feed the same population. As not all the land was as fertile, we can estimate that 1 family (6 to 10 persons) needed some 30 hectares arable land to feed itself. 10 hectares laid at any given year in waste. 10 hectares gave in theory sufficient crops, given the fact that today, with the help of modern fertilizers and seed varieties, the yield is at least 10 times greater. So, 1 hectare produces today as much as 10 hectares in the 5th century.
(3) Meadows were as much needed. Cattle was very important. It provided a secondary source of food and income, especially when the staple crops failed. Horses were the only mean of transport and the most important source of power. 10 hectares of meadows per family is a conservative estimation. Most of time, it was land that was less suited for growing crops.
(4) Woodland was also very important. Wood was the main building material and was the only mean to warm the farm. Here too, at least 10 hectares of forest seems necessary, although it stood upon the least valuable grounds. It's a common mistake to believe that there were more forests in Britain 2000 years ago than today. The reality was that the farmers had chopped all woods upon fertile and arable land. One cannot eat wood.

All land was exploited up to its maximal sustainability. The idea that vast virgin forest subsisted in western Europe is false. 4000 years of agriculture managed to transform the landscape profoundly [1].

In total, 1 family needed an estimated 50 hectares to subsist. The 50 hectares, a mix of arable land, meadows and woods, is a theoretical average. This means that in some regions the woods would dominate, while in other regions arable land would. Fertile soil meant that less land was needed, let's say some 20 up to 30 hectares. The local climate is also very important.

The United Kingdom has today a surface of 250 000 km2. In hectares: 25 million. Divided by 50 (per family) gives: 500 000 families. In number of persons: between 3 million up to 5 million. The truth is in between: some 4 million is a good estimation. Not all of Britain is suited for farming. The Scottish highlands are much less suited than the southeast of England, or the Salisbury plains. One can estimate that only 1/3 of Britain is really suited for agriculture (arable land and good meadows).

This leads us to the following rule : The European population 2000 years ago was in general some 10% of the modern one. This figure must be corrected per region. In the colder North one can subtract around 20% from the amount, in the warm South one can add 20 %. In Scotland and Scandinavia the actual population figures were considerably lower.
The calculation for Italy = 60 million today = 6 million at the time of Julius Caesar, but given the excellent climate which is well suited for Mediterranean crops, we can add 20% = 7 up to 8 million. Italy always was the most fertile and richest region in the Mediterranean basin. The real power of Rome was derived from superior agricultural output in Italy.

How can we verify those figures? By checking with the size of the professional armies the Romans disposed of. A militia represents between 6% up to 10% of the total population (this population includes of course all women and children - 35% was younger than 20 years). 6% is the figure for the first battle, 10% is reached when the war lasts for a long time (repeated recruitments). A professional army represents 10% of the possible militia (or 0,6% - 1% of the population). Those figures are valid for the whole world and any period. Let's not forget that the occupation of a soldier is very demanding, especially in ancient times [2].
As Italy had an estimated population of 7 million, so the possible professional army, at a rate of 1 % is 70 000 men. Or in legions: 70 000 / 6 000 = 11,67 or 12 legions. But the Romans recruited also outside Italy. Rome's army was in fact bigger (estimated at 120.000 men). The real recruitment percentage was smaller (0,6%) and more recruitment happened outside Italy.
In 48 BC, after the war in Gaul, Julius Caesar had an army of 8 legions or 8*6000= 48 000 men (some speak about 11 legions), although many legions had not been repleted. Several legions like Legio V Alaudae also called Gallica (Southern France) and Legio III Gallica , were entirely recruited amongst populations outside Italy. Many others had a mixed recruitment base, even with south-German (or Austrian) volunteers in the cavalry regiments.
Their training and war experience had made them very skilled. No wonder Caesar had ambitions.

The same calculations can be applied to the Nervian army, a militia. The tribe controlled some 10 000 km2 or 1 000 000 hectares (1/3 of modern Belgium). As the country is flat and fertile, we take 30 hectares per family. Total estimated population: 260 000 people. The militia at a rate of 7 % = 18 200 men. A professional soldier is generally worth 2 militia men. The reason is his superior weaponry, experience and discipline. Most Gauls fought with hunting weapons (cfr. Caesar). Only 1 in 10 had a full war gear. Caesar’s army counted at the moment of the battle of the Sabis (against the Nervians), some 44 000 fully equipped professionals. To be a match for this army, the Nervians needed at least 70 000 men, even taken in account their courage. A numerical superiority of 30% is a minimal requirement, or some 59 000 men. Caesar wrote that a part of the Nervian army had to remain in their homeland to counter the German raiders he had sent. So, an optimistic figure for the Nervian army is some 13 000 men on the banks of the small Sabis river. 2 other tribes assisted them with in total an approximate 6000 men. It becomes clear that the Nervians had little chance to win, even if their army had been entirely professional.
The figures of the Belgian armies Caesar gave us, are clearly exaggerated. According to these numbers, all the (mentioned) Belgian armies counted some 268 000 men in total. Were those figures to be correct, then Belgium had according to Caesar a population (I take 6%) of 4.5 million, that is, more than Britain. Twice as much as the Belgian army in 1914.

How big was Rome?

 

How much inhabitants had Rome itself during the first century AD, the age of greatest power? Rome was without a doubt the biggest city of Europe. Some historians claim that Rome had some 1 million inhabitants at the height of its power. Other historians lower this figure to a more modest 500 000 inhabitants. But how to calculate that?

First method: In 1800 the average percentage of city-dwellers in Western Europe was 10% of the total population. This figure is well attested. During the Roman Empire I can estimate this percentage at 5% average. The land had to feed the cities, so the more food the land was able to produce, the more city-dwellers were possible. The yield of the land in AD 50 was probably half of the yield in 1800 as the total European population at that moment also was double the figure of AD 50. Example: France under Napoleon had 20 million inhabitants. The reason is a much better agricultural technology in 1800. Therefore: 5% in AD 50.

Italy had during the first century an estimated population of 7 million. The country was the richest and therefore the most populated one of the Mediterranean region. Italy was the power engine of the Empire. The estimated total city population at 5% = 350 000. Pompeii had an estimated population of 10 000. There were at least 12 cities with this number of inhabitants in Italy (=120 000). Some cities like Mediolano (Milan) had probably more inhabitants :± 20 000 [3]. So: 150 000 citizens in the important cities. 350 000 - 150 000 = 200 000 left for Rome. But there were also a lot of smaller cities with something like 5000 inhabitants. In fact, Italy has countless villages. Let's say: 30 = 150 000 total lived in the villages. 200 000 - 150 000 = 50 000 left for Rome (estimated error margin: 20%). But we know that Italy was not able to feed Rome. Grain had to come from Egypt for instance. It was mainly the Mediterranean region which fed Rome during the first century AD.
At its greatest extend the Roman Empire counted some 45 - 50 million inhabitants. North of the Pyrenees lived an estimated 16 million people (Gaul: 8 million +Britain: 4 million +, the Germano-Romans (from Belgium to Austria): 4 million = 16). Before the Roman conquest of those regions, the Empire had some 45-16 = 20 up to 23 million inhabitants. We must subtract Italy itself: 20-7 = 13 or 14 million. 14 million at 5% = 700 000 city inhabitants in the regions outside Italy.
If we add 100 000 inhabitants to Rome (50 000 + 100 000), then those 100 000 represented 14% of the total of all cities under the rule of the Roman republic except Italy (100 000 people of 700 000 = 13%).
If we add 200 000 then it's 28%, or almost a third of the total city population around the Mediterranean Sea, except Italy. Then the yield surplus must have been greater than 5%, at least some 7,5% - which is unlikely given the rather dry climate. Only fertile Egypt was capable of such a thing, but not every single year. As Egypt had some 5 million inhabitants, (3000 000 hectare at some 1,7 persons per hectare), the calculation is: 7,5% of 5 million= 375 000. To able to feed the 100 000 citizens extra in Rome meant that almost one third of the Egyptian surplus was destined for Rome. When Marcus Antonius halted the shipping of grain to Rome, the food situation in Rome rapidly deteriorated.
In theory, other regions could have supplied Rome too, but none were as fertile as Egypt. North Africa could at best feed some 40 000 extra Roman inhabitants. What becomes very clear is that Rome never could have more than 250 000 inhabitants. Given the fact that harvests were not always optimal in Egypt and North Africa, I can add 120 000 inhabitants to the initial 50 000 [4].
Conclusion of the first calculation method:
Total estimated population of Rome during the 1st century was about 170 000. The error margin is a sketchy 20%.

A second method to estimate the number of inhabitants is to calculate the surface of Rome and to compare it with a medieval city. This medieval city is the rich city of Bruges. The assumption is that building technology was similar, as was the density of the population. Medieval Bruges had an attested 40 000 - 45 000 inhabitants. Its inner surface is some 430 hectares. The Aurelian city walls of Rome were build in AD 271. The total area within the walls is some 1370 hectares. Rome had thus an area 1370/430= 3,18 times bigger than Bruges. Its population can therefore be estimated at 45 000 * 3,18 = 145 000. Again, an error margin of 20% has to be considered. Given the fact that Rome had, in contrast to Bruges, apartment buildings, we can estimate that this figure corresponds with the previous calculation.

At the time of Julius Caesar, 50 BC, Rome was had say 80 000 - 90 000 inhabitants. The area within the republican walls (until 40 BC) is also known and at least half the size of the city in AD 271.

Consider the historic statistical average that the number of professional soldiers represent something between 0.5% up to 1.5% of the total population. For belligerent Rome I'm prepared to go up to 5 % (almost the size of a militia). This means that Rome itself was capable of delivering only one single legion (=5000 legionnaires) at best! As the total Roman army during the age of Caesar had an estimated 120 000 soldiers, then we can only conclude that the Romans recruited the bulk of their soldiers outside Rome itself. At least 90% of the Roman soldiers were therefore NOT from the city itself but other Italians, south Gaul, Spaniards, etc.

It is also a common mistake to believe that the Roman senators originated from the city itself. Most senators came from other regions, but the idea was that they could rule the city. Ruling the city meant ruling the Empire. This was the Roman system: the incorporation of foreigners into the center of power. That's one very important reason why the Empire lasted so long. The Roman army was based upon the same system, 95% of the legionnaires were not recruited in Roma city.

Check: When the Empire fell, Rome had an estimated population of 50 000 - 60 000. The city needed no longer to import grain from Egypt.

 

Britain

 

Britain could feed in theory some 200 000 city inhabitants. Considering the not always ideal climate, it must have been closer to 160 000. This represents 32 cities with 5000 inhabitants. Some cities were bigger. London, Caerleon, and a few others had closer to 10 000 inhabitants. Maybe 5 or 6 cities had more than 5000 inhabitants, leaving only 20 cities with less than 5000 inhabitants. And what about the many villages? In reality Britain had more 'cities', which makes the average size of a British town smaller. Compare : in 1821 the population of Sheffield had reached 31 314 inhabitants. Today it's close to 530 000.