Magnitude of Great Lisbon Earthquake may have been lower than previous estimates

The magnitude of the Great Lisbon Earthquake event, a historic and devastating earthquake and tsunami that struck Portugal on All Saints' Day in 1755, may not be as high as previously estimated.

In his study published in the Bulletin of the Seismological Society of America, Joao F. B. D. Fonseca at the Universidade de Lisboa used macroseismic data -- contemporaneous reports of shaking and damage -- from Portugal, Spain and Morocco to calculate the earthquake's magnitude at 7.7. Previous estimates placed the earthquake at magnitude 8.5 to 9.0.
Fonseca's analysis also locates the epicenter of the 1755 earthquake offshore of the southwestern Iberian Peninsula, and suggests the rupture was a complicated one that may have involved faulting onshore as well. This re-evaluation could have implications for the seismic hazard map of the region, he said.
The current maps are based on the assumption that most of the region's crustal deformation is contained in large offshore earthquakes, without a significant onshore component. "While the current official map assigns the highest level of hazard to the south of Portugal, gradually diminishing toward the north, the interpretation now put forward concentrates the hazard in the Greater Lisbon area," said Fonseca.
The 1755 Lisbon earthquake and tsunami event, along with the fires it caused that burned for hours in the city, is considered one of the deadliest earthquake events in history, leading to the deaths of about 12,000 people. The devastation had a significant impact on Portugal's economy and its political power within Europe, and its philosophical and theological implications were widely discussed by Enlightenment scholars from Voltaire to Immanuel Kant.

Early humans revealed to have engineered optimized stone tools at Olduvai Gorge

University of Kent

Early Stone Age populations living between 1.8 - 1.2 million years ago engineered their stone tools in complex ways to make optimised cutting tools, according to a new study by University of Kent and UCL.
The research, published in the Journal of Royal Society Interface, shows that Palaeolithic hominins selected different raw materials for different stone tools based on how sharp, durable and efficient those materials were. They made these decisions in conjunction with information about the length of time the tools would be used for and the force with which they could be applied. This reveals previously unseen complexity in the design and production of stone tools during this period.
The research was led by Dr Alastair Key, from Kent's School of Anthropology and Conservation, and is based on evidence from mechanical testing of the raw materials and artefacts found at Olduvai Gorge in Tanzania -- one of the world's most important sites for human origins research.
Dr Key collaborated with Dr Tomos Proffitt, from UCL Institute of Archaeology, and Professor Ignacio de la Torre of the CSIC-Centro de Ciencias Humanas y Sociales in Madrid, for the study.
Their research, which employed experimental methods more commonly used in modern engineering research, shows that hominins preferentially selected quartzite, the sharpest but least durable stone type at Olduvai for flake tools; a technology thought to have been used for expedient, short-lived cutting activities.
Chert, which was identified as being highly durable and nearly as sharp as quartzite, was only available to hominins for a short 200,000 year period. Whenever it was available, chert was favoured for a variety of stone tool types due to its ability to maximise cutting performance over extended tool-use durations. Other stone types, including highly durable lavas, were available at Olduvai, however their use varied according to factors such as how long a tool was intended to be used for, a tools potential to create high cutting forces, and the distance hominins had to travel to raw material sources.
The study reveals a level of complexity and flexibility in stone tool production previously unseen at this time. Earlier research had demonstrated Early Stone Age populations in Kenya to select highly durable stone types for tools, but this is the first time cutting edge sharpness has been able to be considered. By selecting the material best suited to specific functional needs, hominins optimised the performance of their tools and ensured a tools efficiency and 'ease-of-use' was maximised.
Dr Key said: 'Why Olduvai populations preferentially chose one raw material over another has puzzled archaeologists for more than 60 years. This has been made all the more intriguing given that some stone types, including lavas and quartzite, were always available.
'What we've been able to demonstrate is that our ancestors were making quite complex decisions about which raw materials to use, and were doing so in a way that produced tools optimised for specific circumstances. Although we knew that later hominin species, including our own, were capable of such decisions, it's amazing to think that populations 1.8 - 1.2 million years ago were also doing so.'
Dr Proffitt added: 'Early hominins during the Oldowan were probably using stone flakes for a variety of tasks. Mostly for butchering animals whilst scavenging, but also probably for cutting various plants and possibly even shaping wood. A durable cutting edge would have been an important factor when using these tools.
'There are many modern analytical techniques used in material sciences and engineering that can be used to interrogate the archaeological record, and may provide new insights into the mechanical properties of such tools and artefacts. By understanding the way that these tools work and their functional limits it allows archaeologists to build up a greater understanding of the capabilities of our earliest ancestors at the dawn of technology.'
The team now hopes that researchers at other archaeological sites will want to apply similar mechanical tests and techniques to help understand the behaviour of Stone Age populations.

Over-hunting walruses contributed to the collapse of Norse Greenland

IMAGE: Church ruins from Norse Greenland's Eastern Settlement. view more 

Credit: James H. Barrett

The mysterious disappearance of Greenland's Norse colonies sometime in the 15th century may have been down to the overexploitation of walrus populations for their tusks, according to a study of medieval artefacts from across Europe.
Founded by Erik the Red around 985AD after his exile from Iceland (or so the Sagas tell us), Norse communities in Greenland thrived for centuries - even gaining a bishop - before vanishing in the 1400s, leaving only ruins.
Latest research from the universities of Cambridge, Oslo and Trondheim has found that, for hundreds of years, almost all ivory traded across Europe came from walruses hunted in seas only accessible via Norse settlements in south-western Greenland.
Walrus ivory was a valuable medieval commodity, used to carve luxury items such as ornate crucifixes or pieces for games like chess and Viking favourite hnefatafl. The famous Lewis chessmen are made of walrus tusk.
However, the study also indicates that, as time wore on, the ivory came from smaller animals, often female; with genetic and archaeological evidence suggesting they were sourced from ever farther north - meaning longer and more treacherous hunting voyages for less reward.
Increasingly globalised trade saw elephant ivory flood European markets in the 13th century, and fashions changed. There is little evidence of walrus ivory imports to mainland Europe after 1400.
Dr James H. Barrett, from the University of Cambridge's Department of Archaeology, argues that the Norse abandonment of Greenland may have been precipitated by a "perfect storm" of depleted resources and volatile prices, exacerbated by climate change.
"Norse Greenlanders needed to trade with Europe for iron and timber, and had mainly walrus products to export in exchange," said Barrett, lead author of the study published in Quaternary Science Reviews.
"We suspect that decreasing values of walrus ivory in Europe meant more and more tusks were harvested to keep the Greenland colonies economically viable."
"Mass hunting can end the use of traditional haul-out sites by walruses. Our findings suggest that Norse hunters were forced to venture deeper into the Arctic Circle for increasingly meagre ivory harvests. This would have exacerbated the decline of walrus populations, and consequently those sustained by the walrus trade."
Other theories for collapse of the colonies have included climate change - the "Little Ice Age", a sustained period of lower temperatures, began in the 14th century - as well as unsustainable farming methods and even the Black Death.
"An overreliance on walrus ivory was not the only factor in Norse Greenland's demise. However, if both the population and price of walrus started to tumble, it must have badly undermined the resilience of the settlements," says co-author Bastiaan Star of the University of Oslo. "Our study suggests the writing was on the wall."
Analysis using carved artefacts would risk damage, so researchers examined pieces of "rostrum": the walrus skull and snout to which tusks remained attached during shipment, creating a protective "package" that got broken up in the ivory workshops of medieval trading centres such as Dublin, Trondheim and Bergen.
In total, the team studied 67 rostra taken from sites across Europe, dating between the 11th and 15th century. Ancient DNA (25 samples) and stable isotopes (31 samples) extracted from samples of bone, as well as tusk socket size, provided clues to the animals' sex and origins.
The stable isotope analysis was conducted by Cambridge's Dorothy Garrod Laboratory for Isotopic Analysis, and the DNA analysis by Oslo's Department of Biosciences.
The researchers also studied traces of "manufacturing techniques" - changing styles of butchery and skull preparation - to help place the walrus remains in history.
While impossible to determine exact provenance, the researchers detected a shift in European walrus finds around the 13th century to walruses from an evolutionary branch most prevalent in the waters around Baffin Bay.
These animals must have been hunted by sailing northwest up the Greenland coast, and more recent specimens were smaller and often female. "If the original hunting grounds of the Greenland Norse, around Disko Bay, were overexploited, they may have journeyed as far north as Smith Sound to find sufficient herds of walrus," said Barrett.
Norse artefacts have previously been found among the remains of 13th and 14th century Inuit settlements in this most northern of regions. One former Inuit camp on an islet off Ellesmere Island contained the rivets of a Norse boat - quite possibly a hunting trip that never returned.
"Ancestors of the Inuit occupied northern Greenland during the time of the Norse colonies. They probably encountered and traded with the Norse," said Barrett. "That pieces of a Norse boat were found so far north hints of the risks these hunters might have ended up taking in their quest for ivory."
Barrett points out that the Inuit of the region favoured female walruses when hunting, so the prevalence of females in Greenland's later exports could imply a growing Norse reliance on Inuit supply.
He says that hunting season for the Norse would have been short, as seas were choked with ice for much of the year. "The brief window of summer would have barely been sufficient for rowing the many hundreds of miles north and back."
The legend of Erik the Red itself may mask what Barrett calls "ecological globalisation": the chasing of natural resources as supply dwindles. Recent research revealed that Greenland might have been settled only after Icelandic walruses were hunted to exhaustion.
Ultimately, having been highly prized for centuries, the marbled appearance of walrus ivory fell out of favour as West African trade routes opened up, and the homogenous finish of elephant ivory became de rigueur in the 13th century.
One account suggest that in the 1120s, Norse Greenlanders used walrus ivory to secure their own bishopric from the King of Norway. By 1282, however, the Pope requests his Greenland tithes be converted from walrus tusk into silver or gold.
"Despite a significant drop in value, the rostra evidence implies that exploitation of walruses may have even increased during the thirteen and fourteenth centuries," said Barrett.
"As the Greenlanders chased depleted walrus populations ever northwards for less and less return in trade, there must have come a point where it was unsustainable. We believe this 'resource curse' undermined the resilience of the Greenland colonies."

Ancient Potter's Secret 'Piggy Bank' Uncovered in 1,200-Year-Old Ceramics Kiln in Israel

1,200 year old hoard of gold coins found in Israel Antiquities Authority excavations at Yavneh

“Hanukka Gelt” was found last week during archaeological excavations in Yavneh during excavations conducted by the Israel Antiquities Authority (IAA) prior to the development of a new neighborhood at the behest of the Israel Lands Authority. The archaeologists were surprised to discover a broken clay juglet containing gold coins dating to the Early Islamic period. The excavations revealed an ancient industrial area which was active for several hundred years, and the archaeologists suggest that the shiny treasure may have been a potter’s personal “piggy bank”.

“I was in the middle of cataloging a large number of artifacts we found during the excavations when all of a sudden I heard shouts of joy” said Liat Nadav-Ziv, co-director alongside Dr. Elie Haddad of the excavation on behalf of the IAA. “I ran towards the shouting and saw Marc Molkondov, a veteran archaeologist of the IAA approaching me excitedly. We quickly followed him to the field where we were surprised at the sight of the treasure. This is without a doubt a unique and exciting find especially during the Hanukkah holiday”.

Liat Nadav-Ziv and Marc Molkondov with the hoard. Photo: Amihai Tamir, courtesy of the Israel Antiquities Authority

Inspection of the Yavneh gold coins conducted by Dr. Robert Kool, an expert on ancient coins at the IAA, dates the coins to the early Abbasid Period (9th century CE). Among the coins, is a gold Dinar from the reign of the Caliph Haroun A-Rashid (786-809 CE), on whom the popular story “Arabian Nights” also known as “One Thousand and One Nights” was based. “The hoard also includes coins that are rarely found in Israel” says Dr. Kool. “These are gold dinars issued by the Aghlabid dynasty that ruled in North Africa, in the region of modern Tunisia, on behalf of the Abbasid Caliphate centered in Bagdad…Without a doubt this is a wonderful Hanukkah present for us” concludes Dr. Kool. 

The Hoard. Photo: Liat Nadav-Ziv, Courtesy of the Israel Antiquities Authority.

The large-scale excavation, carried out southeast of Tell Yavneh, revealed an unusually large amount of pottery kilns that was active at the end of the Byzantine and beginning of the Early Islamic period (7th– 9th centuries CE). The kilns were for commercial production of store-jars, cooking pots and bowls. The gold hoard was found inside a small juglet, near the entrance to one of the kilns and according to the archaeologists could have been the potter’s personal savings.

In a different area of the site, the remains of a large industrial installation were revealed dating to the Persian period (4th– 5th centuries BCE) and used for the production of wine. According to Dr. Haddad of the IAA “initial analysis of the contents of the installation revealed ancient grape pips (seeds). The size and number of vats found at the site indicated that wine was produced on a commercial scale, well beyond the local needs of Yavneh’s ancient inhabitants.”

The 7 gold coins were found in a small broken jar near a pottery kiln, and may have been a potter's personal piggy bank.

(Image: © Liat Nadav-Ziv, Israel Antiquities Authority)

As Hanukkah ended last week, archaeologists in central Israel discovered a hidden trove of 1,200-year-old coins near an ancient pottery studio in the city of Yavne, between Jerusalem and the Mediterranean Sea. In a news release, researchers from the Israeli Antiquities Authority (IAA) likened the stash of seven gold pieces to "Hanukkah gelt" (those foil-covered chocolate coins that bless Jewish parents with eight nights of stains to clean up), though the coins date to the ninth century, when Israel was under Islamic rule.
According to Robert Kool, a coin expert with the IAA, one of the pieces reportedly dates to the reign of Caliph Haroun A-Rashid (A.D. 786-809), who later became a central character in the folk story collection "One Thousand and One Nights."

"The hoard also includes coins that are rarely found in Israel," Kool said in a statement. These include gold coins issued by Islamic rulers in North Africa (in modern-day Tunisia), Kool said.

Photo Credit: Liat Nadav-Ziv, Israel Antiquities Authority

A closer look at the coins. (Image credit: Liat Nadav-Ziv, Israel Antiquities Authority)

Archaeologists found the coins in a small broken jug near the entrance to one of many ancient pottery kilns in Yavne, which appears to have been a hub of commercial pottery production from the seventh to the ninth centuries. Ceramic pots were versatile vessels used for storage, food preparation and dining, but the broken pot that contained the coins may have been a potter's personal "piggy bank," the team said.
The kiln was uncovered during a large-scale excavation of Yavne, prior to the construction of a new neighborhood there. Other sections of the dig have revealed significantly older buildings, including a wine-making facility dating to the Persian period (fourth to fifth century B.C.). The facility included way more wine vats than would have been needed to satisfy the local population, the archaeologists wrote, which means Yavne was likely a booming center of wine production — and therefore would have probably been a fun place to celebrate Hanukkah, after all.

Findings Point to Site of Jerusalem’s Millennia-Old Marketplace on Pilgrimage Road

Photo Credit: Ari Levi, Antiquities Authorities

Helene Machline, Israel Antiquities Authority Archaeologist, with the table portion.

The top of a rare 2000-year-old measuring table used for liquid items such as wine and olive oil has been discovered in what appears to have been a major town square along the Pilgrimage Road in Jerusalem. The discovery was made during excavations conducted by the Israel Antiquities Authority in the City of David National Park.

The top part of the measuring table / Ari Levi, Israel Antiquities Authorities

In addition to the measuring table, tens of stone measuring weights were also discovered in the same vicinity. These all support the theory that this was the location of the main city square and market on route to the Temple during the Second Temple Period, in what was historically known as Jerusalem’s lower city. It appears that the market served as the focal point of trade and commerce. Researchers suggest that this area housed the offices of the Agoranomos, the official in the cities of ancient Greece and Byzantine Empire that controlled the order of the marketplace (agora).

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According to Prof. Ronny Reich, who is currently researching the recent discovery, “we see two of the deep cavities that remained in a portion of the ‘standard of volumes’ table uncovered in the City of David, each with a drain at its bottom. The drain at the bottom could be plugged with a finger, filled with a liquid of some type, and once the finger was removed, the liquid could be drained into a container, using the measurement table as a uniform guideline to determining the volume of the container. This way, traders could calibrate their measuring instruments using a uniform standard.”

The bottom part of the measuring table / Ari Levi, Israel Antiquities Authorities

Reich adds that “this is a rare find. Other stone artifacts were very popular in Jerusalem during the Second Temple, however, so far, excavations in Jerusalem have only uncovered two similar tables that were used for measuring volume – one in the 1970s excavations in the Jewish Quarter, and another in the Shu’afat excavations, in northern Jerusalem.”
According to archaeologist Ari Levi of the IAA, one of the directors of the excavations of the Pilgrimage Road, “the Pilgrimage Road excavations in the City of David have also revealed a great number of stone scale-weights measuring different values. These weights are of the type which was commonly used in Jerusalem. The fact that there were city-specific weights at the site indicates the unique features of the economy and trade in Jerusalem during the Second Temple period, possibly due to the influence of the Temple itself.”
The Stone scale-weights have a flat, round shape, and they are made in different sizes, representing different masses. According to Reich, more than 90% of all stone weights of this type, totaling several hundreds, were found in archaeological excavations in early Jerusalem, dating back to the Second Temple period, and they represent a unique Jerusalem phenomenon.

The Pilgrimage Road at the City of David / Kobi Harati, City of David archive

IAA researchers Nahshon Szanton, Moran Hagbi and Meidad Shor, who directed the excavations along the Pilgrimage Road, uncovered a large, open, paved area dating back some 2000 years, along the street leading up to the Second Temple. They suggest that it served as the main square of the lower city, where trade activity would have taken place in this part of the city.
According to Ari Levi, “the volume standard table we’ve found, as well as the stone weights discovered nearby, support the theory that this was the site of vast trade activity, and perhaps this may indicate the existence of a market.”

Early modern humans cooked starchy food in South Africa, 170,000 years ago

The discovery also points to food being shared and the use of wooden digging sticks to extract the plants from the ground

University of the Witwatersrand

IMAGE: Hypoxis angustifolia growth habit. view more 

Credit: Prof. Lyn Wadley/Wits University

"The inhabitants of the Border Cave in the Lebombo Mountains on the Kwazulu-Natal/eSwatini border were cooking starchy plants 170 thousand years ago," says Professor Lyn Wadley, a scientist from the Wits Evolutionary Studies Institute at the University of the Witwatersrand, South Africa (Wits ESI). "This discovery is much older than earlier reports for cooking similar plants and it provides a fascinating insight into the behavioural practices of early modern humans in southern Africa. It also implies that they shared food and used wooden sticks to extract plants from the ground."
"It is extraordinary that such fragile plant remains have survived for so long," says Dr Christine Sievers, a scientist from the University of the Witwatersrand, who completed the archaeobotanical work with Wadley. The underground food plants were uncovered during excavations at Border Cave in the Lebombo Mountains (on the border of KwaZulu-Natal Province, South Africa, and eSwatini [formerly Swaziland]), where the team has been digging since 2015. During the excavation, Wadley and Sievers recognised the small, charred cylinders as rhizomes. All appear to belong to the same species, and 55 charred, whole rhizomes were identified as Hypoxis, commonly called the Yellow Star flower. "The most likely of the species growing in KwaZulu-Natal today is the slender-leafed Hypoxis angustifolia that is favoured as food," adds Sievers. "It has small rhizomes with white flesh that is more palatable than the bitter, orange flesh of rhizomes from the better known medicinal Hypoxis species (incorrectly called African Potato)."
The Border Cave plant identifications were made on the size and shape of the rhizomes and on the vascular structure examined under a scanning electron microscope. Modern Hypoxis rhizomes and their ancient counterparts have similar cellular structures and the same inclusions of microscopic crystal bundles, called raphides. The features are still recognisable even in the charred specimens. Over a four-year period, Wadley and Sievers made a collection of modern rhizomes and geophytes from the Lebombo area. "We compared the botanical features of the modern geophytes and the ancient charred specimens, in order to identify them," explains Sievers.
Hypoxis rhizomes are nutritious and carbohydrate-rich with an energy value of approximately 500 KJ/100g. While they are edible raw, the rhizomes are fibrous and have high fracture toughness until they are cooked. The rhizomes are rich in starch and would have been an ideal staple plant food. "Cooking the fibre-rich rhizomes would have made them easier to peel and to digest so more of them could be consumed and the nutritional benefits would be greater," says Wadley.
Wooden digging sticks used to extract the plants from the ground "The discovery also implies the use of wooden digging sticks to extract the rhizomes from the ground. One of these tools was found at Border Cave and is directly dated at circa 40,000 years ago," says co-author of the paper and co-director of the excavation, Professor Francesco d'Errico, (Centre National de la Recherche Scientifique (CNRS), Université de Bordeaux, France and University of Bergen, Norway). Dr Lucinda Backwell (Instituto Superior de Estudios Sociales, ISES-CONICET, Tucumán, Argentina) also co-authored the paper and was a co-director of the excavation.
The plants were cooked and shared The Hypoxis rhizomes were mostly recovered from fireplaces and ash dumps rather than from surrounding sediment. "The Border Cave inhabitants would have dug Hypoxis rhizomes from the hillside near the cave, and carried them back to the cave to cook them in the ashes of fireplaces," says Wadley. "The fact that they were brought back to the cave rather than cooked in the field suggests that food was shared at the home base. This suggests that the rhizomes were roasted in ashes and that, in the process, some were lost. While the evidence for cooking is circumstantial, it is nonetheless compelling."
Discoveries at Border Cave This new discovery adds to the long list of important finds at Border Cave. The site has been repeatedly excavated since Raymond Dart first worked there in 1934. Amongst earlier discoveries were the burial of a baby with a Conus seashell at 74,000 years ago, a variety of bone tools, an ancient counting device, ostrich eggshell beads, resin, and poison that may once have been used on hunting weapons.
The Border Cave Heritage Site Border Cave is a heritage site with a small site museum. The cave and museum are open to the public, though bookings are essential [Olga Vilane (+27) (0) 72 180 4332]. Wadley and her colleagues hope that the Border Cave discovery will emphasise the importance of the site as an irreplaceable cultural resource for South Africa and the rest of the world.
About Hypoxis angustifolia
Hypoxis angustifolia is evergreen, so it has visibility year-round, unlike the more common deciduous Hypoxis species. It thrives in a variety of modern habitats and is thus likely to have had wide distribution in the past as it does today. It occurs in sub-Saharan Africa, south Sudan, some Indian Ocean islands, and as far afield as Yemen. Its presence in Yemen may imply even wider distribution of this Hypoxis plant during previous humid conditions. Hypoxis angustifolia rhizomes grow in clumps so many can be harvested at once. "All of the rhizome's attributes imply that it could have provided a reliable, familiar food source for early humans trekking within Africa, or even out of Africa," said Lyn Wadley. Hunter-gatherers tend to be highly mobile so the wide distribution of a potential staple plant food would have ensured food security.

Time-to-death of Roman emperors followed distinct pattern

Roman emperors faced a high risk of violent death in their first year of rule, but the risk slowly declined over the next seven years, according to an article published in the open access journal Palgrave Communications. When statistically modelled, the length of time from the beginning of their reign until their death followed a set pattern, similar to that seen in reliability engineering, interdisciplinary research by Dr Joseph Saleh, an Aerospace Engineer from the Georgia Institute of Technology, US suggests.
Historical records show that of 69 rulers of the unified Roman Empire, 43 (62%) suffered violent deaths either by assassination, suicide or during combat. Historical accounts typically examine each death as a single, random event alongside individual contributing factors such as allegiances and wealth. It is not known whether there were any common, underlying patterns to how long each emperor's reign lasted before they died.
By applying statistical methods frequently used to test the reliability of components in engineering, Dr Joseph Saleh modelled the typical length of time between the beginning of an emperor's reign and their subsequent death. The author found parallels between the seemingly random failures of components in engineering and the seemingly random deaths of emperors.
Dr Saleh said: "In engineering, the reliability of a component or process is defined as the probability that it is still operational at a given time. The time it takes for a component or process to fail is referred to as its time-to-failure and this shows similarities to the time-to-violent-death of Roman emperors."
Dr Saleh found that Roman emperors faced a high risk of violent death during their first year of reign, a pattern also seen when engineering components fail early, often as a result of a failure to function as intended or, in the case of an emperor, meet the demands of their role. The risk of death stabilised by the eighth year but increased again after 12 years of rule, a pattern similar to the failure of components because of fatigue, corrosion or wear-out. When data points were aligned on a graph, the failure rate of Roman emperors displayed a bathtub-like curve, a model widely seen with mechanical and electrical components.
Dr Saleh said: "It's interesting that a seemingly random process as unconventional and perilous as the violent death of a Roman emperor--over a four-century period and across a vastly changed world--appears to have a systematic structure remarkably well captured by a statistical model widely used in engineering. Although they may appear as random events when taken singularly, these results indicate that there may have been underlying processes governing the length of each rule until death."
Data was obtained from the De Imperatoribus Romanis, a peer-reviewed online encyclopedia of Roman emperors. The author cautions that the limitations of the data should be acknowledged, as sources of ancient history are often inconsistent and the exact causes of death may differ between accounts. Further studies could explore why emperors repeatedly met a violent end and whether other historical events may be analysed in this way.