Prehistoric Life During the Miocene Epoch

Prehistoric Life During the Miocene Epoch The Miocene epoch marks the stretch of geologic time when prehistoric life (with some notable exceptions in South America and Australia) substantially resembled the flora and fauna of recent history, due in part to the long-term cooling of the earths climate. The Miocene was the first epoch of the Neogene period (23-2.5 million years ago), followed by the much shorter Pliocene epoch (5-2.6 million years ago); both the Neogene and Miocene are themselves subdivisions of the Cenozoic Era (65 million years ago to the present). Climate and Geography As during the preceding Eocene and Oligocene epochs, the Miocene epoch witnessed a continuing cooling trend in the earths climate, as global weather and temperature conditions approached their modern patterns. All of the continents had long since separated, though the Mediterranean Sea remained dry for millions of years (effectively joining Africa and Eurasia) and South America was still completely cut off from North America. The most significant geographic event of the Miocene epoch was the slow collision of the Indian subcontinent with the underside of Eurasia, causing the gradual formation of the Himalayan mountain range. Terrestrial Life During the Miocene Epoch Mammals. There were a few notable trends in mammalian evolution during the Miocene epoch. The prehistoric horses of North America took advantage of the spread of open grasslands and began to evolve toward their modern form; transitional genera included Hypohippus, Merychippus and Hipparion (oddly enough, Miohippus, the Miocene horse, actually lived during the Oligocene epoch!) At the same time, various animal groups - including prehistoric dogs, camels, and deer - became well-established, to the point that a time traveler to the Miocene epoch, encountering a proto-canine like Tomarctus, would immediately recognize what type of mammal she was dealing with. Perhaps most significantly, from the perspective of modern humans, the Miocene epoch was the golden age of apes and hominids. These prehistoric primates mostly lived in Africa and Eurasia, and included such important transitional genera as Gigantopithecus, Dryopithecus, and Sivapithecus. Unfortunately, apes and hominids (which walked with a more upright posture) were so thick on the ground during the Miocene epoch that paleontologists have yet to sort out their exact evolutionary relationships, both to each other and to modern Homo sapiens. Birds. Some truly enormous flying birds lived during the Miocene epoch, including the South American Argentavis (which had a wingspan of 25 feet and may have weighed as much as 200 pounds); the slightly smaller (only 75 pounds!) Pelagornis, which had a worldwide distribution; and the 50-pound, sea-going Osteodontornis of North America and Eurasia. All of the other modern bird families had pretty much been established by this time, although various genera were a bit larger than you might expect (penguins being the most notable examples). Reptiles. Although snakes, turtles, and lizards continued to diversify, the Miocene epoch was most notable for its gigantic crocodiles, which were nearly as impressive as the plus-sized genera of the Cretaceous period. Among the most important examples were Purussaurus, a South American caiman, Quinkana, an Australian crocodile, and the Indian Rhamphosuchus, which may have weighed as much as two or three tons. Marine Life During the Miocene Epoch Pinnipeds (the mammalian family that includes seals and walruses) first came into prominence at the end of the Oligocene epoch, and prehistoric genera like Potamotherium and Enaliarctos went on to colonize the rivers of the Miocene. Prehistoric whales - including the gigantic, carnivorous sperm whale ancestor Leviathan and the sleek, gray cetacean Cetotherium - could be found in oceans worldwide, alongside enormous prehistoric sharks like the 50-ton Megalodon. The oceans of the Miocene epoch were also home to one of the first identified forebears of modern dolphins, Eurhinodelphis. Plant Life During the Miocene Epoch As mentioned above, grasses continued to run wild during the Miocene epoch, especially in North America, clearing the way for the evolution of fleet-footed horses and deer, as well as more stolid, cud-chewing ruminants. The appearance of new, tougher grasses toward the later Miocene may have been responsible for the sudden disappearance of many megafauna mammals, which were unable to extract sufficient nutrition from their favorite menu item.

The U.S. Militarys Space Operations

The U.S. Militarys Space Operations People love a good military conspiracy theory, including the one that the Air Force has its very own space shuttle. It all sounds very James Bond, but the truth is that the military actually never had a secret space shuttle.  Instead, it used NASAs space shuttle fleet until 2011. Then it built and flew its own mini-shuttle drone and continues to test it on long missions. However, while there may be great interest within the military for a space force, theres just not one out there. There is a space command at the U.S. Air Force, mainly interested in working through issues of armed forces using space resources. However, there arent phalanxes of soldiers up there, just a lot of interest in what military use of space might eventually become. The U.S. Military in Space The  theories about the military use of space stem largely from the fact that the U.S. Department of Defense flew secret missions on the shuttles when NASA was still using them to get to space. Interestingly, when NASAs fleet was being developed, there were plans to make  additional copies exclusively for military purposes. That affected the specifications of the shuttle design, such as the length of its glide path, so that the vehicle could accommodate military and top-secret missions. There was also a shuttle launch facility built in California, at Vandenberg Air Force Base. This complex, called SLC-6 (Slick Six), was supposed to be used to put shuttle missions into polar orbits. However, after the Challenger exploded  in 1986, the complex was put into caretaker status and was never used for a shuttle launch. The facilities were mothballed until the military decided to retool the base for satellite launches. It was used to support Athena launches until 2006 when Delta IV rockets began to lift off from the site.   Use of the Shuttle Fleet for Military Operations Ultimately, the military decided that having dedicated shuttlecraft for the military was unnecessary. Given the amount of technical support, staff, and facilities required to run such a program, it made more sense to use other resources to launch payloads into space. In addition, more sophisticated spy satellites were developed to accomplish reconnaissance missions. Without its own fleet of shuttles, the military relied on NASAs vehicles to meet its needs for access to space. In fact, the space shuttle Discovery was planned to be available to the military as its exclusive shuttle, with civilian use as it was available. It was even going to be launched from the militarys Vandenbergs SLC-6 launch complex. Ultimately the plan was scrapped following the Challenger disaster. In recent years, the space shuttle fleet has been retired and new spacecraft are being designed to take humans to space.   For years, the military used whatever shuttle was available at the time of need, and military payloads were launched from the usual launchpad at Kennedy Space Center. The last shuttle flight strictly for military use was carried out in 1992 (STS-53). The subsequent military cargo was taken up by shuttles as a secondary part of their missions. Today,  with the increasingly reliable use of rockets via NASA and SpaceX (for example), the military has much more cost-effective access to space.   Meet the X-37B Mini-shuttle Drone While the military hasnt had a need for a conventional manned orbiting vehicle, some situations could call for a shuttle-type craft.  However, these craft will be quite different from the current stable of orbiters- perhaps not in look, but definitely in function. The X-37 shuttle  is a good example of where the military is going with a shuttle-type spacecraft. It  was originally designed as a potential replacement for the current shuttle fleet. It had its first successful flight in 2010, launched from atop a rocket. The  craft carries no crew, its missions are secret, and it is entirely robotic. This mini-shuttle has flown several long-term missions, most likely performing reconnaissance flights and specific types of experiments.   Clearly, the military is interested in the ability to place objects into orbit as well as have reusable spy craft; the expansion of projects like the X-37 thus seems entirely possible and very likely will continue into the foreseeable future. The U.S. Air Force space command, with bases and units around the globe, is the front line for space-based missions, and also focuses on cyberspace capabilities for the country, as needed.   Could There Ever Be a Space Force? Occasionally politicians float  the idea of a space force. What that force would be or how it would be trained are still very large unknowns. There are few facilities to get soldiers ready for the rigors of fighting in space. As well, theres been no talk by veterans of such training, and expenditures for such places would eventually show up in budgets. However, if there was to be a space force, massive changes to military structures would be needed. As mentioned, training would have to ramp up on a scale so far unknown to any military on the planet. Thats not to say one couldnt be created in the future, but there isnt one now.   Edited and updated by Carolyn Collins Petersen.