Paleo Profiles: Megatherium

A Megatherium, from the London Natural History Museum

Visitors to the Natural History Museum in London in the second half of the nineteenth century gasped in awe upon seeing a giant skeleton. Visitors today may do so at the animatronic Tyrannosaurus, the long-necked sauropod Camarasaurus, or perhaps Dippy, the Diplodocus who until recent years dominated the Entrance Hall. However, in the 1800s the guests were not gasping at a dinosaur as they would today - instead they were in awe of a sloth. The Megatherium was one of the largest mammals to ever walk on land; only the largest of mammoths, elephants, and the great Paraceratherium exceeded it in size. 

Discovery and Fossils

Megatherium has been known to science for a long time - long before science officially described dinosaurs. In 1788 on the banks of the Lujan River in Argentina Manuel Torres came across several large bones which were then shipped to Madrid where they were stored in the Museo National de Ciencias Naturales. This coincided with the European Enlightenments which have been seen as one of the intellectual movements which gave rise to present-day science. As a result, anatomists and early biologists were eager to examine newly found bones, and live specimens. Eventually, an anatomist named Georges Cuvier - a French anatomist and biologist who would be considered to be a 'founding father' of palaeontology. Looking at the bones he described them as resembling that of a sloth - originally he even stated that, like sloths, it lived in the trees - except that these bones were from an animal the size of an elephant. His paper in 1796 named this extinct animal Megatherium americanum, 'Giant best from America'. Cuvier continued studying Megatherium eventually changing his mind on the sloth's biology; he argued it really lived a subterranean life using its big arms and claws to dig tunnels. He was half correct; Megatherium could dig but it did not lead a subterranean life.

Georges Cuvier

We have many examples of Megatherium fossils from across South America. It was an incredibly diverse animal having eight different species which occupied all of the continent from Patagonia in the south to Colombia in the north. Close cousins of the Megatherium also dominated the southern US and Central America as well. Normally, palaeontologists have to deal with a few remains and, therefore, have to reconstruct animals from better preserved relatives or logical guesses. The number of complete skeletons we have of Megatherium means that we do not have that issue in this case.  On his voyage with the Beagle Charles Darwin even brought some skeletons back with him in the 1830s. Other genus of ground sloths have even given us fossilised hair and droppings which paints a better picture of what the Megatherium was like in life. 

Biology

The size of the Megatherium from Prehistoric-Wildlife.com

The ground sloths share a basic body shape with their relatives in the trees, except that their bodies have adapted for life on the land instead. The hind legs are short with the lower bones being as thick as the femur; they had short but thick tails; robust bones; a broad pelvis; and a low body - this allowed the Megatherium to eat from the trees while remaining firmly on the ground. A stable lower-body allowed the sloth to raise itself onto two feet to browse from the trees. Its upper body was surprisingly flexible to reach branches; prehensile lips (with a possible prehensile tongue) to choose the best foliage; and strong, muscular jaws to effectively cut through the vegetation. As this animal was feeding it would rear up, using its tail as a tripod to steady itself, and then use its arms and lips to physically feed. The Megatherium's hands were also decked out in five curved claws which could be up to 70-cm (around 2.4-foot) in length. These could be used to tear leaves from the trees or bend branches closer to its mouth - or alternatively be used as a weapon. Megatherium would have walked on all-fours, but from footprints we know that it could spend considerable amounts of time in a bipedal stance. Even when on all-fours it had a unique way of walking; to protect its claws from unnecessary wear it would walk on the sides of its feet. Pictured below is a relative of the sloths - the giant anteater. Like the Megatherium they are heavily reliant on their claws so when they walk in a quadrapedal stance they do so on their knuckles.

A giant anteater walking on its knuckles, from Arkive by Joe Kolowski, Accessed 05/01/2019

Megatherium was in the Order Pilosa which included other giant ground sloths, and today is comprised of modern sloths, anteater, and tamanduas. Expanding it out slightly they also belong to the Superorder Xenarthra which also includes armadillos - the giant armadillo even walks like a ground sloth. The Megatherium differs thanks to its size - the largest were 6 metres long (20 foot) and weighed up to 4 tonnes. Modern elephants are of an equivalent size. A lot of this came from the animal's bones and muscles - it was big to make itself stable. As a result, adult Megatherium had little to fear in regards to predators. However, due to its size, weight being at the lower half of the body, and walking style this made Megatherium a slow animal.

When and Where

An example of the Great Interchange, Wikipedia - the blue originated in the North, the olive the South

One of the reasons why we have so many Megatherium fossils is due to it living quite recently. Megatherium first appeared in the early Pliocene, sometime between 5 and 3 million years ago, or when humanity's first ancestors started becoming bipedal. Megatherium's ancestors evolved during a time of great change. Moving continents lead to the creation of the Isthmus of Panama bridging the gap between North and South America. This severed the link between the Atlantic and warmer waters leading the Atlantic, and also the Arctic and Antarctic, to become much cooler. Two continents now being connected allowed animals to migrate: deer, camelids, and big cats were just some who moved south as sloths, giant terror birds, and hummingbirds were just some who moved north. Hence, we have sloths closely related to Megatherium living in Central and North America. The Eromotherium was so similar to Megatherium that it was once, and sometimes still is, classed as Megatherium. As giant ground sloths existed in woodlands and grasslands this have them a wide area to call home - we have found Megatherium for that reason in nine countries, the most recent being found in the Peruvian Andes. Existing throughout the Ice Age it managed to last until the last few thousand years. We can even carbon date the youngest Megatherium fossils, and the giant sloths went extinct around 8,500 BCE.

Diet

Like existing sloths Megatherium was adapted to eating plants. Their jaws were adapted to slice through thick foliage allowing them to browse from the trees as well as through various grasses and agaves found in America's grasslands. Most of this is not speculation either. Fossilised dung from Megatherium and other ground sloths have shown us their diets - inside the fossilised droppings we find a wide variety of plants, in one up to over 70 different types. However, Richard Fariña and Ernesto Blanco have put forward a controversial theory: Megatherium could be an omnivore. They argued that short triceps meant that Megatherium could move its arms quickly making its claws an effective weapon. They did stress that Megatherium was not a hunter - instead, using its immense size, it would scare predators from their kills to supplement their diets. The BBC documentary Walking with Beasts portrayed it as doing exactly that. This theory has been criticised in recent years. Palaeontologists have pointed out that we likely would have found claw marks from sloths or evidence in dung if meat was such a large part of their diet to be classed as an omnivore. Zoologists have found deer eating baby birds in the wild and hippos even cannibalising one another so it is not too far-fetched for Megatherium to occasionally scavenge. Undoubtedly, the Megatherium would almost entirely be herbivorous.

Habitat

A Megatherium in its habitat in Walking with Beasts

Megatherium lived in the grasslands and woodlands across South America - imagine llaneros herding their cattle today and coming across a giant ground sloth. Their bodies being adapted to an occasional bipedal lifestyle would indicate that woodlands, or the outskirts of woodlands, would be the ideal habitat for a Megatherium. They would live alongside a wide variety of fauna including the lama like Macrauchenia, a giant armadillo (the size of a small car) with a clubbed tail called Doedicurus, the terror birds (two metre tall predator birds), and the Smilodon, better known as the sabre-toothed cat. A fully grown Megatherium would have no fear, other than other sloths, but younger ones would have potential predators. Smaller ground sloths, although still fairly large, in North America have been found to have dug holes. This could be a potential way to clean themselves - dirt baths are particularly effective way to clear fur from ticks - but also a potential place to hide from a predator. They likely had one predator: humans.

Extinction

Megatherium is one of the first animals lost in the Sixth Mass Extinction - the mass extinction caused by humanity. When humanity expanded into Europe, Australasia, and the Americas most of the megafauna went extinct - including the giant sloths. We even have fossil evidence to show that humans did hunt smaller cousins to the Megatherium - cuts and breaks on sloth bones show evidence that humans had used their bodies for resources. It is quite likely that Megatherium could have met the same fate. One theory has suggested that humans accidentally caused a mass extinction as fauna went extinct thanks to disease introduced by domesticated animals. However, humans were not the only reason why the sloth went extinct. From around 12,000 years ago the climate started rapidly changing - which has been suggested why humanity adopted farming - which drastically affected habitats worldwide. Climate change had restricted Megatherium's habitat which started driving the sloth into extinction - human hunters ensured that it did go extinct. Megatherium was joined in extinction by the rest of the ground sloths as well as much of the megafauna of the Americas.

Thank you for reading. The sources I have used are as follows:

-'Megatherium', Prehistoric-Wildlife.com, (Accessed 04.01/2019)

-Jeremy Green and Daniela Kalthoff, 'Xenarthran Dental Microstructure and Dental Microwear Analyses, with New Data for Megatherium americanum (Megatheriidae)', Journal of Mammology, 96:4, (2015), 645-658

-Gideon Mantell, 'The Megatherium', Scientific American, 37:7, (1852), 291

-'Sabre Tooth',Walking with Beasts, (2001), BBC, 13 December

-M. Susana Bargo, 'The ground sloth Megatherium americanum: Skull shape, bite forces, and diet',  Acta Palaeontologica Polonica, 46:2, (2001), 173-192

-Francois Pujos, 'Megatherium celendinense sp. nov. from the Pleistocene of the Peruvian Andes and the phylogenetic relationships of Megatheriines', Palaeontology, 49:2, (2006), 285-306

-Pip Brewer, 'What was Megatherium?', Natural History Museum, (22/11/2018), Accessed 04/01/2019
-Tim Haines and Paul Chambers, The Complete Guide to Prehistoric Life, (London: BBC Books, 2005)

Thank you for reading. For other Paleo Profiles we have a list here. For future blog updates please see our Facebook or catch me on Twitter @LewisTwiby.

World History: The Little Ice Age

Peter Breughel the Elder's Hunters in the Snow

When we think about history we often forget about the climate and environment, but it has been incredibly influential in shaping human history. The last time we looked properly at the climate as a part of World History it was our very first post describing the evolution of humanity; there changing global climate caused grasslands to encroach on forests and forced our ancestors to walk upright, (please see here). Climate has never stopped affecting human history and today I want to focus specifically on a period of climate history named the Little Ice Age, something which lasted from the mid-fifteenth century to the mid-nineteenth century. First coined by Francois E. Matthes in 1939 historians now have taken note of the significance of the Little Ice Age and its impact on our history.

How do we know it happened?

Changing Global Temperature

Quite often historians have been criticized for making statements with the idea 'we weren't there so we can't be certain.' Although at times this is a valid criticism but for the Little Ice Age we do have evidence that it took place. Climatologists and meteorologists have used ice-cores and dendrochronology (looking at tree rings) which show us that from around 1300 the world's climate got much colder, reaching a peak in the seventeenth century, and then getting warmer in the 1800s. Geoffrey Parker in his article Crisis and Catastrophe has shown through a series of graphs how fewer sunspots were seen, temperatures were lower, and increased volcanic activity happened during this time period. Not only that, we have cultural evidence that global temperatures dropped during this time period. Pictured at the top of this post if Peter Breughel the Elder's Hunters in the Snow painted in 1565 depicting hunters walking through thick snow as people ice skate on a frozen ponds. A painting by Abraham Hondius in 1676 depicted hunters chasing a fox on the frozen Thames, and until the mid-nineteenth century carnivals on the frozen Thames were a regular occurrence. We have written records also of severe climate and weather conditions. In 1641 Enomoto Yazaemon wrote that on New Year's Day 'ice lay in the fields one foot deep. From that time, I observed seven snowfalls until the spring.' Chronicler Benedikt Kuen in the 1680s wrote about the glacier Vernagtferner moving south from the Alps:

in 1600. so our ancestors tell us, the big glacier behind Rofen after it had come into the valley according to its habit, broke out on the feast of St James [25 July], did great damage to the fields in the Ezthal, spoilt the roads and streets and carried away all the bridges. In the parish of Langenfeld the water flooded the ground from Rethlstain to Lener Kohlstatt.

In the 1640s governor of the Massachusetts Bay Colony noted in his journal: 

The frost was so great and continual this winter that all the Bay was frozen over, so much and so long, as the like, by the Indians' relation, had not been so these forty years ... To the southward also the frost was as great and the snow as deep, and at Virginia itself the great [Chesapeake] bay was much of it frozen over, and all of their great rivers.

Volcanic eruptions, independent of global climate, added to global cooling periodically. 1816 was described by contemporaries as 'The Year Without a Summer' following the eruption of Mt. Tambora the year prior. We can even use wine harvests to provide evidence for the Little Ice Age; before 1469 wine was actually cultivated in England which ended through colder temperatures.

A Thames Frost Fair

How It was Explained

Today we know that the adverse climate was due to the Little Ice Age, but we have the benefit of hindsight and decades of scientific research on climate. Contemporaries did not have that benefit so looked at ways which they understood the world to explain the floods, hail, and storms. We'll look at two areas of the world and how they understood the causes: Europe and China.

We'll discuss China first. Throughout World History when we've discussed China one phrase has repeatedly cropped up, 'the Mandate of Heaven.' For those who are new to the term the Mandate of Heaven was the idea that the ruling dynasty only ruled thanks to a mandate directly from Heaven. However, if the ruling dynasty was seen as being corrupt or decadent, abusing its citizens, or just generally inept it was believed that the mandate would leave the ruling dynasty. Any new dynasty which ousted the old one could now claim that they have the Mandate of Heaven. Since the fourteenth century the Ming had ruled China and by the seventeenth century Chinese society had changed. Years of relative peace and prosperity had caused a population boom in the countryside putting pressure on the land, a thriving domestic (and a smaller external) trade had caused merchants to become wealthier than farmers, and inflation was rapidly rising through the importation of silver from the Americas and Japan. The floods, hail, storms, and cooler temperatures brought on by the Little Ice Age led to crop failures compounding the issue, and nothing causes a revolt quicker than starving people. To contemporaries it was clear that the Mandate of Heaven had left the Ming and they pointed to the weather as a sign of it. The violent weather was seen as a sign that the Ming were no longer protected by Heaven, and that this was a sign that the Ming should be replaced. In 1644 the Ming were overthrown and their successors, the Shun, were overthrown shortly after by the new Qing Dynasty.

A depiction of a witch burning from England in the 1640s

Europe did not point to their rulers as the cause of bad weather, hail and red suns but instead turned to the Bible. Wolfgang Behringer has linked the Little Ice Age to the spike in witch hunts. From 1560 to 1600 somewhere between 100,000 and 200,000 people were accused of witchcraft where 40,000 to 60,000 were executed. Before Pope Innocence VIII released his papal bull Summis desiderantus affectibus on 5 December 1484 the Church did not link witchcraft to the weather, and Innocence only did this at the request of Dominican friar Heinrich Kramer. Often the sins of the populace were blamed for the weather but smaller political entities were more susceptible to the idea of witches. A very severe thunderstorm hit central Europe on 3 August 1562 during a time of meteorological events which people in the Barony of Illeraichen blamed on witches which forced Count Hans von Rechberg to imprison several women who confessed to witchcraft under torture. Between 1562 and 1565 in Wiesensteig there was an attempt to eradicate 'the evil' in society where 63 women were burnt as witches. A chronicler in the Franconian town of Zeil in 1626 wrote:

Everything froze, something which had not happened as long as one could remember, causing a big rise in prices. […] As a result, pleading and begging began among the rabble, who questioned why the authorities continued to tolerate the witches. […] Thus the prince-bishop punished these crimes

Accusations were heavily gendered. Between 75 and 85 per cent of those accused were women, but in Northern Europe more men were accused than women. However, there were pushbacks against the idea of witches causing the bad weather. As mentioned many in the Church blamed the sins of the people and at times ridiculed the idea of witches. The idea of familiars was mocked with some clergy commenting if Satan really wanted to cause damage; wouldn't he become a dragon instead of a cat? Humanists looked to secular reasons and centers of secularization like Nuremburg and the Swiss and Italian-republics, despite ruling lots of rural land, saw little to no witch burnings. Scholar Albrecht Durer produced woodcuts presenting the subject as a way for people to portray beautiful women naked. Across Europe reaction to the Little Ice Age varied.

The Crisis of the Seventeenth Century

Historians Eric Hobsbawm and Hugh Trevor-Roper argued in the 1950s that the 1600s saw a 'Crisis' where the world was plunged into increased violence. Hobsbawm, a primarily European historian, argued this crisis was part of Europe's transition from feudalism to capitalism, whereas Trevor-Roper linked this to a political crisis where the modern political state started to emerge. The 1600s were a violent time in history: over a million took part in revolts in China, peasant revolts swept over Switzerland and Germany, rebellions hit Russia in 1648 and 1649, a series of revolts in Brazil, the overthrow of the Kongo Kingdom, the brutal collapse of the Ming, the Mughal Civil War, a spike in the amount of people made slaves for the Atlantic Slave Trade, the Fronde in France, a succession war in the Ottoman Empire, the Wars of the Three Kingdoms in the British Isles, and the Thirty Years' War are just some of the violence to strike the world. Geoffrey Parker reopened the debate but spoke of a global crisis, not just a European one. He went on to link this to the Little Ice Age. Although the Little Ice Age did not cause these conflicts and bouts of violence it helped contribute to them. Using the example of China the collapse of the Ming was down to poor harvests and other factors, and the Manchus who succeeded them, (excluding the brief Shun Dynasty), moved south to China as they believed that China would have better harvests than Manchuria. Parker himself can sum this idea best:

How, precisely, can historians link the harsh winters, cool summers, droughts, and floods of the 1640s […] with individual cases of state breakdown such as the revolts of Scotland, Ireland and England against Charles I, or the collapse of Ming rule in China? We must not paint bull’s-eyes around bullet holes and argue that since climatic aberrations seem to be the only factor capable of causing simultaneous upheavals around the globe, therefore those aberrations “must” have caused the upheavals.

Depiction of the Thirty Years' War

The Little Ice Age amplified causes for war and violence throughout the world. A two per cent drop in global temperatures can halve a rice harvest, which happened. This would help explain some of the origins of a revolt but not all of them. Despite rice or grain harvests becoming smaller taxes on land remained the same and often crops were sent to the cities instead of staying in the countryside. When more crops remained in the countryside riots broke out in cities as the price of food, like bread, rose. Furthermore, the various wars which swept the world added to these issues. Soldiers would pillage the countryside for food helping cause famines, and with less food your immune system is weaker so this helped spread disease. War, disease and famine during the Thirty Years' War caused a population decline of up to 40 per cent in the German states and in China the word binghuo (soldier calamity) was coined to describe the pillaging of the country by soldiers. 

Image of the Fronde

Before we conclude I just want to talk about the demographic shift thanks to the Little Ice Age. When people were tired of war, persecution and famine they moved. The 1600s saw the largest surge of colonists to the Americas and, unfortunately with it, slaves from Africa as well. A Chinese diaspora also began in the early 1600s with many settling in areas like Malaysia and the Philippines which would open up these areas for migration in the 1800s. At times when food was in short supply through bad harvests family sizes decreased and in some areas, like northern Europe, they largely remained small. We can see as well the difference in wealth as well. A general trend in Europe was that wealthy families, who could afford food, had larger families whereas less wealthy families had smaller families. There also began a trend of marrying later, and in Renaissance Europe quite often widows did not remarry. However, there were darker sides to this. In the 1680s the Qing passed a decree to prevent widow suicides indicating that it must have been an endemic problem and several European states, like France, passed strict laws against infanticide. Children who died under the age of five were sometimes checked to make sure they died naturally and were not murdered. 

Conclusion

New Orleans after Hurricane Katrina

The Little Ice Age offers a prime example for us to learn from history. As I am writing we are faced with dramatic climate change caused by global warming. During the last hurricane season the United States was hit by several destructive hurricanes - Harvey, Irma and Maria to name just three - most likely as a result of climate change. Alongside these hurricanes we had intense wild fires in California and floods in Chad, India, Nepal and Nigeria. Geoffrey Parker put forward the Little Ice Age as one of the causes of the Crisis of the Seventeenth Century a few years after Hurricane Katrina and was deeply influenced by this. It is widely believed that the reason why the Little Ice Age ended was because of the Industrial Revolution which poured carbon dioxide in unprecedented numbers into the atmosphere causing global temperatures to rise. By looking at how the Little Ice Age affected communities of the past we can find ways to cope with the climate issues which we face today.

The sources I have used are as follows:

-Geoffrey Parker, 'Crisis and Catastrophe: The Global Crisis of the Seventeenth Century Reconsidered,' The American Historical Review, 113:4, (2008), pp. 1053-1079

-Wolfgang Behringer, 'Climate Change and Witch-Hunting: The Impact of the Little Ice Age on Mentalities,' Climate Change, 43:1, (1999), pp. 335-351

-Crash Course World History: The Little Ice Age

-Brian Fagan, The Little Ice Age: How Climate Made History, 1300-1850, (New York: Basic Books, 2000)

-Tom Bristow and Thomas H. Ford, (eds.), A Cultural History of Climate Change, (New York: Routledge, 2016)
-Wolfgang Behringer, A Cultural History of Climate, (London: Wiley, 2009)

-Jean M. Grove, The Little Ice Age, (London: Methuen, 1988)

Thank you for reading. Next time we'll be looking at one of the most significant events in European history which saw its 500th anniversary this October: the Reformation. For future blog updates we have a Facebook or you can get me on Twitter @LewisTwiby.

For other World History posts we have a collection of them here.