Prehistoric Life During the Pliocene Epoch

Prehistoric Life During the Pliocene Epoch By the standards of deep time, the Pliocene epoch was relatively recent, commencing only five million years or so before the start of the modern historical record, 10,000 years ago. During the Pliocene, prehistoric life around the globe continued to adapt to the prevailing climatic cooling trend, with some notable local extinctions and disappearances. The Pliocene was the second epoch of the Neogene Period (23-2.6 million years ago), the first being the Miocene (23-5 million years ago); all of these periods and epochs were themselves part of the Cenozoic Era (65 million years ago to the present). Climate and Geography During the Pliocene epoch, the earth continued its cooling trend from previous epochs, with tropical conditions holding at the equator (as they do today) and more pronounced seasonal changes at higher and lower latitudes; still, average global temperatures were 7 or 8 degrees (Fahrenheit) higher than they are today. The major geographic developments were the reappearance of the Alaskan land bridge between Eurasia and North America, after millions of years of submersion, and the formation of the Central American Isthmus joining North and South America. Not only did these developments allow an interchange of fauna between three of the earths continents, but they had a profound effect on ocean currents, as the relatively cool Atlantic ocean was cut off from the much warmer Pacific. Terrestrial Life During the Pliocene Epoch Mammals. During large chunks of the Pliocene epoch, Eurasia, North America, and South America were all connected by narrow land bridges- and it wasnt all that difficult for animals to migrate between Africa and Eurasia, either. This wreaked havoc on mammalian ecosystems, which were invaded by migrating species, resulting in increased competition, displacement, and even outright extinction. For example, ancestral camels (like the huge Titanotylopus) migrated from North America to Asia, while the fossils of giant prehistoric bears like Agriotherium have been discovered in Eurasia, North America, and Africa. Apes and hominids were mostly restricted to Africa (where they originated), though there were scattered communities in Eurasia and North America. The most dramatic evolutionary event of the Pliocene epoch was the appearance of a land bridge between North and South America. Previously, South America had been much like modern Australia, a giant, isolated continent populated by a variety of strange mammals, including giant marsupials. Confusingly, some animals had already succeeded in traversing these two continents, before the Pliocene epoch, by the arduously slow process of accidental  island-hopping; thats how Megalonyx, the Giant Ground Sloth, wound up in North America. The ultimate winners in this Great American Interchange were the mammals of North America, which either wiped out or greatly diminished their southern relatives. The late Pliocene epoch was also when some familiar megafauna mammals appeared on the scene, including the Woolly Mammoth in Eurasia and North America, Smilodon (the Saber-Toothed Tiger) in North and South America, and Megatherium (the Giant Sloth) and Glyptodon (a gigantic, armored armadillo) in South America. These plus-sized beasts persisted into the ensuing Pleistocene epoch, when they went extinct due to climate change and competition with (combined with hunting by) modern humans. Birds. The Pliocene epoch marked the swan song of the phorusrhacids, or terror birds, as well as the other large, flightless, predatory birds of South America, which resembled meat-eating dinosaurs that had gone extinct tens of millions of years earlier (and count as an example of convergent evolution.) One of the last surviving terror birds, the 300-pound Titanis, actually managed to traverse the Central American isthmus and populate southeastern North America; however, this didnt save it from going extinct by the start of the Pleistocene epoch. Reptiles. Crocodiles, snakes, lizards, and turtles all occupied an evolutionary backseat during the Pliocene epoch (as they did during much of the Cenozoic Era). The most important developments were the disappearance of alligators and crocodiles from Europe (which had now become much too cool to support these reptiles  cold-blooded lifestyles), and the appearance of some truly gigantic turtles, such as the aptly named Stupendemys of South America. Marine Life During the Pliocene Epoch As during the preceding Miocene, the seas of the Pliocene epoch were dominated by the biggest shark that ever lived,  the 50-ton Megalodon. Whales continued their evolutionary progress, approximating the forms familiar in modern times, and pinnipeds (seals, walruses, and sea otters) flourished in various parts of the globe. An interesting side note: the marine reptiles of the Mesozoic Era known as  pliosaurs  were once thought to date from the Pliocene epoch, hence their misleading name, Greek for Pliocene lizards. Plant Life During the Pliocene Epoch There werent any wild bursts of innovation in Pliocene plant life; rather, this epoch continued the trends seen during the preceding Oligocene and Miocene epochs: the gradual confinement of jungles and rain forests to equatorial regions, while vast deciduous forests and grasslands dominated higher northern latitudes, especially in North America and Eurasia.

Zheng Hes Treasure Ships of the Ming Dynasty

Zheng Hes Treasure Ships of the Ming Dynasty Between 1405 and 1433, Ming China under the rule of Zhu Di, sent out enormous armadas of ships into the Indian Ocean commanded by the eunuch admiral Zheng He. The flagship and other largest treasure junks dwarfed European ships of that century; even  Christopher Columbuss flagship, the Santa Maria, was between 1/4 and 1/5 the size of Zheng Hes. Drastically changing the face of Indian Ocean trade and power, these fleets embarked on seven epic voyages under Zheng Hes guidance, resulting in a rapid expansion of Ming Chinas control in the region, but also of their struggle to maintain it in years to come due to the financial burden of such endeavors. Sizes According to Ming Chinese Measurements All of the measurements in the remaining Ming Chinese records of the Treasure Fleet are in a unit called zhang, which is made up of ten chi or Chinese feet. Although the exact length of a zhang and chi has varied over time, the Ming chi was probably about 12.2 inches (31.1 centimeters) according to Edward Dreyer. For ease of comparison, the measurements below are given in English feet. One English foot is equivalent to 30.48 centimeters. Incredibly, the largest ships in the fleet (called baoshan, or treasure ships) were likely between 440 and 538 feet long by 210 feet wide. The 4-decked baoshan had an estimated displacement of 20-30,000 tons, roughly 1/3 to 1/2 the displacement of modern American aircraft carriers. Each had nine masts on its deck, rigged with square sails that could be adjusted in series to maximize efficiency in different wind conditions. The Yongle Emperor ordered the construction of an amazing 62 or 63 such ships for Zheng Hes first voyage, in 1405. Extant records show that another 48 were ordered in 1408, plus 41 more in 1419, along with 185 smaller ships throughout that time. Zheng Hes Smaller Ships Along with dozens of baoshan, each armada included hundreds of smaller ships. The eight-masted ships, called machuan or horse ships, were about 2/3 the size of the baoshan  measuring approximately 340 feet by 138 feet. As indicated by the name, the machuan carried horses along with timber for repairs and tribute goods. Seven-masted liangchuan or grain ships carried rice and other food for the crew and soldiers in the fleet. Liangchuan was about 257 feet by 115 feet in size. The next ships in descending order of size were the zuochuan, or troopships, at 220 by 84 feet with each transport ship having six masts. Finally, the small, five-masted warships or zhanchuan, each about 165 feet long, were designed to be maneuverable in battle. Though tiny compared with the baochuan, the zhanchuan were more than twice as long as Christopher Columbuss flagship, the Santa Maria. The Treasure Fleets Crew Why did Zheng He need so many huge ships? One reason, of course, was shock and awe. The sight of these enormous ships appearing on the horizon one by one must have been truly incredible for the people all along the Indian Oceans rim and would have enhanced Ming Chinas prestige immeasurably. The other reason was that Zheng He traveled with an estimated 27,000 to 28,000 sailors, marines, translators and other crew members. Along with their horses, rice, drinking water, and trade goods, that number of people required a staggering amount of room aboard the ship. In addition, they had to make space for the emissaries, tribute goods and wild animals that went back to China.