The (c. 5.3 to 2.6 mya) began warmer than , but was the prelude to today’s ice age, as temperatures steadily declined. An epoch of less than three million years reflects human interest in the recent past. Geologically and climatically, there was little noteworthy about the Pliocene (although the was created then), although two related events made for one of the most interesting evolutionary events yet studied. South America kept moving northward, and the currents that once in the Tethyan heyday were finally closed. The gap between North America and South America began to close about 3.5 mya, and by 2.7 mya the current land bridge had developed. Around three mya, the began, when fauna from each continent could raft or swim to the other side. South America had been isolated for 60 million years and only received the stray migrant, such as rodents and New World monkeys. North America, however, received repeated invasions from Asia and had exchanges with Europe and Greenland. North America also had much more diverse biomes than South America's, even though it had nothing like the Amazon rainforest. The ending of South America’s isolation provided the closest thing to a controlled experiment that paleobiologists would ever have. South America's fauna was devastated, far worse than European and African fauna were when Asia finally connected with them. More than 80% of all South American mammalian families and genera existing before the Oligocene were extinct by the Pleistocene. Proboscideans continued their spectacular success after leaving Africa, and species inhabited the warm, moist Amazonian biome, as well as the Andean mountainous terrain and pampas. The also invaded and thrived as a mixed feeder, grazing or browsing as conditions permitted. In came cats, dogs, camels (which became the ), horses, pigs, rabbits, raccoons, squirrels, deer, bears, tapirs, and others. They displaced virtually all species inhabiting the same niches on the South American side. All large South American predators were driven to extinction, as well as almost all browsers and grazers of the grasslands. The South American animals that migrated northward and survived in North America were almost always those that inhabited niches that no North American animal did, such as monkeys, (which survived because of their claws), and their small cousins (which survived because of their armor), , and (which survived because of their quills). The opossum was nearly eradicated by North American competition but survived and is the only marsupial that made it to North America and exists today. One large-hoofed herbivore survived: the . The (it weighed one metric ton!) survived for a million years after the interchange. , that , also survived and migrated to North America and lasted about a million years before dying out. In general, North American mammals were , which resulted from evolutionary pressures that South America had less of, in its isolation. They were able to outrun and outthink their South American competitors. South American animals made it past South America, but none of them drove any northern indigenous species of note to extinction.
After Africa began colliding with Asia, about 18 mya Asian animals quickly invaded and dominated Africa. The two primary exceptions were , both of which prospered at home in Africa and in Eurasia. Proboscideans did even better; they did not only become prominent in Eurasia, but they also migrated to North America by 16.5 mya. , as soon as they could, and quickly succeeded in all South American biomes, from rainforest to grasslands to mountains. They beat apes to the Western Hemisphere by 16.5 million years. Elephants have and . Their huge size and prehensile trunks, as well as their ability to eat a wide variety of vegetation, let proboscideans flourish everywhere that they possibly could. They even as a force. Until humans arrived, proboscideans were the most intelligent, adaptable, and successful land mammals ever and arguably outperformed the dinosaurs. But after nearly 20 million years of global success, they nearly all went extinct soon after encountering behaviorally modern humans. They went extinct in the Western Hemisphere, and there has long been controversy among scientists whether humans caused it, although the debate is fading as evidence of human agency becomes clearer.
Photo Essay: The Mountain Gorillas of Rwanda - Go …
The anatomy of habilines (members of ) spoke volumes about their lives. They had brains of about 640 ccs, with an estimated range of 600 to 700 ccs, nearly 50% larger than their australopithecine ancestors and nearly twice that of chimps, and the artifacts they left behind denoted advanced cognitive abilities. They stood about 1.5 meters tall (five feet), and weighed around 50 kilograms (120 pounds). With the first appearance of habilines about 2.3 mya, Oldowan culture spread widely in East Africa and also radiated to South Africa. Habiline skeletal adaptations to tree climbing meant that they slept there at night, just as their ancestral line did. Their teeth were large, which meant that they heavily chewed their food. Habiline sites have large rock hammers that they pounded food on, to break bones and crack nuts. Those habiline stone hammers may well have also been used to soften meat, roots, and other foods before eating them. Sleeping in trees meant that habilines were preyed on, mostly by big cats. Today, the leopard is the only regular predator of chimpanzees and gorillas, and at times. But if modern studies of chimpanzees are relevant, our ancestors engaged in warfare for the past several million years, and , so simian intra-species mass killings may have tens of millions of years of heritage. Habilines were not only wary of predators, but also of members of their own species.
Mountain Gorillas - Research Paper by Wsqaanti
Bonobos have an average party size of about 17, and party sizes are consistent. How can they have such large and stable foraging parties while no other chimps can? Because they eat gorilla food. Because gorillas no longer live south of the Congo, the young leaves and herb stems not available to chimps where gorillas live make for pleasant bonobo traveling snacks. Since the biomass concentration of gorillas and chimps is nearly the same where their ranges overlap, it meant that bonobos had twice the food supply that chimps did. Bonobos also evolved to better digest gorilla foods, and larger parties put females on a more equal footing with males. Bonobos, both males and females, did not tolerate the alpha male model of other chimp societies in which male gangs dominated.
More Endangered species Essay Topics
When chimpanzees eat meat, they put large, tough leaves in their mouths. That helps them overachieve as meat eaters, as their teeth and jaws are poorly adapted for chewing meat. Mountain gorillas eat no meat at all. In the wild, great apes spend about half of their day chewing. Chimpanzees are the most carnivorous great ape, and although meat is the greatest treasure in chimpanzee societies, they often stop eating meat after chewing it for an hour or two and revert to fruit and other softer foods if they can get it. Chimpanzees when their staple, fruit, is scarce. Chimps have been seen killing monkeys, eating their organs, and then abandoning the carcasses to find more monkeys to kill. Organ meats and intestines are far easier to chew, and a poor meat chewer like a chimpanzee prefers soft meats. Just as chimpanzees prefer soft meats, predators will eat soft organs first and leave the tougher muscle for later, if they eat it at all. It depends on how plentiful the available flesh is, but the pattern across all predator groups is clear: eat the best, first, and leave the lesser quality foods to the end or let scavengers have them. It will always be a cost/benefit decision. All things being equal, the less time and energy needed to eat something, the sooner it will be eaten. If extra time and effort is needed to procure food, then the nutritional reward (primarily in energy) has to be exceptional to justify it. Evolutionary pressures have made animals into excellent accountants. The human sweet tooth is a relic of humanity’s fruit-eating ape heritage, and the desire for fatty foods reflects an adaptation to prefer that energy-richest of foods. Fat (made of hydrocarbons) is the ultimate energy windfall of all foods.