ancestors evolved

Scientists have pinpointed the moment in time our earliest ancestors evolved to be warm-blooded, and it happened much later and far more quickly than the researchers expected. An artist's illustration of a mammal ancestor breathing out hot air on a cold night, a hint that it is warm-blooded. © Provided by Live Science An artist's illustration of a mammal ancestor breathing out hot air on a cold night, a hint that it is warm-blooded. The discovery, made by studying the minuscule tubes of the inner ear, places the evolution of mammalian warm-bloodedness at around 233 million years ago — 19 million years later than scientists previously thought. These semicircular canals are filled with a viscous fluid, called endolymph, that tickles tiny hairs lining the canals as the fluid sloshes around. These hairs transmit messages to the brain, giving it instructions for how to keep the body balanced. Like some fluids, the honey-like endolymph gets runnier the hotter it is, requiring the semicircular canals to change their shape so the fluid can still do its job. In ectothermic, or cold-blooded, animals, this ear fluid is colder and thus behaves more like molasses and needs wider spaces in which to flow. But for endothermic, or warm-blooded, animals, the fluid is more watery and small spaces suffice. Enter Your Date Of Birth To Calculate Your Life Insurance Cost Ad QuoteSearch Enter Your Date Of Birth To Calculate Your Life Insurance Cost Related: Ancient toothless 'eel' is your earliest known ancestor This temperature-based property makes tiny, semicircular canals a perfect place to spot the moment when ancient mammals' cold blood turned hot, researchers wrote in a paper published July 20 in the journal Nature. "Until now, semicircular canals were generally used to predict locomotion of fossil organisms," study co-lead author Romain David, an evolutionary anthropologist at the Natural History Museum in London, said in a statement. "However, by carefully looking at their biomechanics, we figured that we could also use them to infer body temperatures. "This is because, like honey, the fluid contained inside semicircular canals gets less viscous [syrupy] when temperature increases, impacting function," David explained. "Hence, during the transition to endothermy, morphological adaptations were required to keep optimal performances, and we could track them in mammal ancestors." To discover the time of this evolutionary change, researchers measured three inner ear canal samples from 341 animals — 243 living species and 64 extinct species — spanning the animal kingdom. The analysis revealed that the 54 extinct mammals included in the study developed the narrow inner ear canal structures suitable for warm-blooded animals 233 million years ago. Before this study, scientists thought mammals inherited warm-bloodedness from the cynodonts — a group of scaly, rat-like lizards that gave rise to all living mammals — that were thought to have evolved warm-bloodedness around the time of their first appearance 252 million years ago. However, the new findings suggest that mammals diverged from their early ancestors more markedly than expected. And this drastic change happened surprisingly fast. Heat-friendly ear canals didn't just appear later in the fossil record than the scientists expected. It happened far more rapidly, too — popping up around the same time the earliest mammals began evolving whiskers, fur and specialized backbones. "Contrary to current scientific thinking, our paper surprisingly demonstrates that the acquisition of endothermy seem[s] to have occurred very quickly in geological terms, in less than a million years," study co-lead author Ricardo Araújo, a geologist at the University of Lisbon in Portugal, said in the statement. "It was not a gradual, slow process over tens of millions of years as previously thought, but maybe was attained quickly when triggered by novel mammal-like metabolic pathways and origin of fur." Follow-up studies will need to confirm the findings via other means, but the researchers said they are excited that their work will help to answer one of the longest-standing questions about the evolution of mammals. "The origin of mammalian endothermy is one of the great unsolved mysteries of paleontology," study senior author Kenneth Angielczyk, the Field Museum's MacArthur curator of paleomammalogy, said in the statement. "Many different approaches have been used to try to predict when it first evolved, but they have often given vague or conflicting results. We think our method shows real promise because it has been validated using a very large number of modern species, and it suggests that endothermy evolved at a time when many other features of the mammalian body plan were also falling into place."

 

Mining in Roman Britain

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Mining was one of the most prosperous activities in Roman Britain. Britain was rich in resources such as copper, gold, iron, lead, salt, silver, and tin, materials in high demand in the Roman Empire. The Romans started panning and puddling for gold. The abundance of mineral resources in the British Isles was probably one of the reasons for the Roman conquest of Britain. They were able to use advanced technology to find, develop and extract valuable minerals on a scale unequaled until the Middle ages.

Contents

• 1Lead mining
• 2Silver extraction
• 3Gold mining
• 4Iron mining
• 5Coal
• 6Working conditions
• 7See also
• 8Notes
• 9References
• 10Further reading
• 11External links

Lead mining[edit]

Roman lead mines at Charterhouse, Somerset

Lead ingots from Roman Britain on display at the Wells and Mendip Museum

Lead was essential to the smooth running of the Roman Empire.^[1] It was used for piping for aqueducts and plumbing, pewter, coffins, and gutters for villas, as well as a source of the silver that sometimes occurred in the same mineral deposits. Fifty-two sheets of Mendip lead still line the great bath at Bath which is a few miles from Charterhouse (see below).

The largest Roman lead mines were located in or near the Rio Tinto (river) in southern Hispania.^[2][3] In Britannia the largest sources were at Mendip, South West England and especially at Charterhouse. In A.D. 49, six years after the invasion and conquest of Britain, the Romans had the lead mines of Mendip and those of Derbyshire, Shropshire, Yorkshire and Wales running at full shift. By A.D.70, Britain had surpassed Hispania as the leading lead-producing province. The Spanish soon lodged a complaint with the Emperor Vespasian, who in turn put limits on the amount of lead being produced in Britain. However British lead production continued to increase and ingots (or pigs) of lead have been found datable to the late second - early third century.^[4] Research has found that British lead (i.e. Somerset lead) was used in Pompeii - the town destroyed in the eruption of Vesuvius in A.D.79.

Silver extraction[edit]

The most important use of lead was the extraction of silver. Lead and silver were often found together in the form of galena, an abundant lead ore. The Roman economy was based on silver, as the majority of higher value coins were minted from the precious metal.

The process of extraction, cupellation, was fairly simple. First, the ore was smelted until the lead, which contained the silver, separated from the rock. The lead was removed, and further heated up to 1100° Celsius using hand bellows. At this point, the silver was separated from the lead (the lead, in the form of litharge, was either blown off the molten surface or absorbed into bone ash crucibles; the litharge was re-smelted to recover the lead), and was put into moulds which, when cooled, would form ingots that were to be sent all over the Roman Empire for minting.^[1][5]

When inflation took hold in the third century A.D. and official coins began to be minted made of bronze with a silver wash, two counterfeit mints appeared in Somerset - one on the Polden Hills just south of the Mendips, and the other at Whitchurch, Bristol to the north. These mints, using Mendip silver, produced coins which were superior in silver content to those issued by the official Empire mints. Samples of these coins and of their moulds can be seen in the Museum of Somerset in Taunton Castle.

Gold mining[edit]

Development of Dolaucothi Gold Mines

The aqueducts at Dolaucothi

Britain's gold mines were located in Wales at Dolaucothi. The Romans discovered the Dolaucothi vein soon after their invasion, and they used hydraulic mining methods to prospect the hillsides before discovering rich veins of gold-bearing quartzite. The remains of several aqueducts and water tanks above the mine are still visible today. The tanks were used to hold water for hushing during prospecting for veins, and involved releasing a wave of water to scour the ground and remove overburden, and expose the bedrock. If a vein was found, then it would be attacked using fire-setting, a method which involved building a fire against the rock. When the hot rock was quenched with water, it could be broken up easily, and the barren debris swept away using another wave of water. The technique produced numerous opencasts which are still visible in the hills above Pumsaint or Luentinum today. A fort, settlement and bath-house were set up nearby in the Cothi Valley. The methods were probably used elsewhere for lead and tin mining, and indeed, were used widely before explosives made them redundant. Hydraulic mining is however, still used for the extraction of alluvial tin.

Long drainage adits were dug into one of the hills at Dolaucothi, after opencast mining methods were no longer effective. Once the ore was removed, it would be crushed by heavy hammers, probably automated by a water wheel until reduced to a fine dust. Then, the dust would be washed in a stream of water where the rocks and other debris would be removed, the gold dust and flakes collected, and smelted into ingots. The ingots would be sent all across the Roman world, where they would be minted or put into vaults.^[1]

Iron mining[edit]

There were many iron mines in Roman Britain. The index to the Ordnance Survey Map of Roman Britain lists 33 iron mines: 67% of these are in the Weald and 15% in the Forest of Dean. Because iron ores were widespread and iron was relatively cheap, the location of iron mines was often determined by the availability of wood, which Britain had in abundance, to make charcoal smelting fuel. Great amounts of iron were needed for the Roman war machine, and Britain was the perfect place to fill that need.^[6]

Many underground mines were constructed by the Romans. Once the raw ore was removed from the mine, it would be crushed, then washed. The less dense rock would wash away, leaving behind the iron oxide, which would then be smelted using the bloomery method. The iron was heated up to 1500 °C using charcoal. The remaining slag was removed and generally dumped.^[6]

After being smelted, the iron was sent to forges, where it was reheated, and formed into weapons or other useful items.

Coal[edit]

For both domestic and industrial use, coal provided a considerable proportion of the fuel required for warmth, metal-working (coal was not suitable for the smelting of iron, but was more efficient than charcoal at the forging stage)^[7] and the production of bricks, tiles and pottery. This is demonstrated by archaeological evidence from sites as far apart as Bath, Somerset (the temple of Sulis and household hypocausts), military encampments along Hadrian's wall (where outcrop coal was worked near the outlying fortlet at Moresby), forts of the Antonine Wall, Carmel lead mines in north Wales and tile kilns at Holt, Clwyd. Excavations at the inland port of Heronbridge on the River Dee show that there was an established distribution network in place. Coal from the East Midlands coalfields was carried along the Car Dyke for use in forges to the north of Duroliponte (Cambridge) and for drying grain from this rich cereal-growing region.^{[8][9] [10][11]} Extraction was not limited to open-cast exploitation of outcrops near the surface: shafts were dug and coal was hewn from horizontal galleries following the coal seams.^[12]

Working conditions[edit]

Fire-setting underground from De Re Metallica

Drainage wheel from Rio Tinto mines

Some miners may have been slaves, but skilled artisans were needed for building aqueducts and leats as well as the machinery needed to dewater mines and to crush and separate the ore from barren rock. Reverse overshot water-wheels were used to lift water, and sequences of such wheels have been found in the Spanish mines. A large section of a wheel from Rio Tinto can be seen in the British Museum, and a smaller fragment of a wheel found at Dolaucothi shows they used similar methods in Britain.

The working conditions were poor, especially when using fire-setting under ground, an ancient mining method used before explosives became common. It involved building a fire against a hard rock face, then quenching the hot rock with water, so that the thermal shock cracked the rock and allowed the minerals to be extracted. The method is described by Diodorus Siculus when he discussed the gold mines of Ancient Egypt in the first century BC, and at a much later date by Georg Agricola in his De Re Metallica of the 16th century. Every attempt was made to ventilate the deep mines, by driving many long adits for example, so as to ensure adequate air circulation. The same adits also served to drain the workings.

See also[edit]

• Derbyshire lead mining history
• Dolaucothi
• Metal mining in Wales
• Naturalis Historia
• Pliny the Elder
• Roman Britain
• Roman engineering
• Roman technology
• Roman metallurgy

Notes[edit]

1. ^ Jump up to:^a b c The Romans in Britain: mining Archived July 20, 2010, at the Wayback Machine
2. ^ http://cat.inist.fr/?aModele=afficheN&cpsidt=2099549 Lead from Carthaginian and Roman Spanish mines isotopically identified in Greenland ice dated from 600 B.C. to 300 A.D. ROSMAN K. J. R.; CHISHOLM W.; HONG S.; CANDELONE J.-P.; BOUTRON C. F.
3. ^ World Ecological Degradation, page 88. Sing C. Chew. Rowman Altamira, 2001. ISBN 0-7591-0031-4, ISBN 978-0-7591-0031-2https://books.google.com/books?id=GM5WOHR55wYC
4. ^ Roman Britain: Industrial layer map Archived September 27, 2006, at the Wayback Machine
5. ^ North, F.J. (1962). "Mining for metals in Wales" (PDF). National Museum of Wales. Retrieved 22 August 2020.
6. ^ Jump up to:^a b Croydon Caving Club Archived November 27, 2006, at the Wayback Machine
7. ^ Sim, David (1 June 2012). "Overview of the technical aspects of iron making". The Roman Iron Industry in Britain. Stroud, UK: The History Press. ISBN 9780752468655.
8. ^ Forbes, R.J. (1958). Studies in ancient Technology. VI. Leiden, Netherlands: Brill. p. 27. OCLC 848445642.
9. ^ Clark, J. G. D. (October 1949). "Report on Excavations on the Cambridgeshire Car Dyke, 1947". The Antiquaries Journal. 29 (3–4): 145–163. doi:10.1017/S0003581500017261.
10. ^ Salway, Peter (2001). A history of Roman Britain. The Society of Antiquaries of London. p. 457. ISBN 9780192801388.
11. ^ Dearne, Martin J.; Branigan, Keith (September 1995). "The Use of Coal in Roman Britain". The Antiquaries Journal. 75: 71–105. doi:10.1017/S000358150007298X.
12. ^ R. G. Collingwood; Nowell Myres (1936). Roman Britain and the English settlements (1990 ed.). New York: Biblo and Tannen. p. 231. ISBN 9780819611604.

References