How long mammals been on earth

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How long have toucans been on Earth? What mammal has been on earth the longest? How long have volcanoes been around? How long have snails been on Earth? How long have beetles been on earth? How long have Cicadas been on earth? Has the earth ever been hit with a asteroid and where? How long has chickens been on earth? They also have four limbs and special pentadactyl ends to these limbs i.

Reptiles, amphibians and even birds — as well as the awe inspiring dinosaurs — are all built around this same simple plan. Before this there were fish, which had the backbone and the skull — but not the pentadactyl limbs. Fish are pretty ancient. They first appeared around million years ago. Nobody lived on land then, only in the seas. By about million years ago, the insects and plants had been dominating the land for around 50 million years, so there was plenty of food for adventurous fish to eat.

If only they could live and move around on the dry, horrible land…. Eventually, some fish transformed their fins into legs and in time they also developed lungs.

Legs for moving and lungs for breathing. The invasion of the land had begun. About 10 million years later, reptiles started to differentiate become different from amphibians and diversity was well underway. Various groups evolved out of these early reptiles including crocodiles, dinosaurs and birds. But most importantly to us, a strange group of animals called the Mammal-like Reptiles. The Mammal-like Reptiles, or Therapsids, first appeared about million years ago — near the beginning of the Permian which is well before the dinosaurs.

They evolved quickly and many different groups arose. They were very successful until about the end of the Permian, about million years ago. Then something catastrophic affected the earth and nearly all of the species then living died out.

New species evolved rapidly to fill this empty habitat. This is another example of convergent evolution. New forms of wildlife continued to arrive in South America even after the continent was cut off from North America. They included primates which gave rise to the New World monkeys, including howler monkey, marmosets, capuchins, woolly monkeys and spider monkeys; and rodents which evolved into a number of families, several of which are found nowhere else in the world.

These include the capybara, the agouti, the coypu, the cavy Guinea pig and the chinchilla. In South America there is a greater variety of rodents than anywhere else in the world. The Invasion of South America. In the upper Pliocene, 3 million years ago, the isthmus of Panama reappeared as a result of changes in the earth's crust.

This was a disaster for many of the animals that had evolved in isolation in South America. South America was invaded by deer, camels, raccoons, tapirs, horses, mastodons, bears, peccaries, rabbits, shrews, cats, dogs, weasels and rodents. For some reason these animals were able to displace many of the South American species, driving many of them to extinction.

Some of the new arrivals e. Others were very successful, for example the camel family which has given rise to the vicunas, guanacos, alpacas and llamas. The camels as well as the horses subsequently became extinct in North America where they originated.

Another group of uniquely South American mammals, the edentates sloths, armadillos and anteaters , survived the competition with the invaders and are still abundant in South America.

The armadillos, like their primitive ancestors, are armor-plated mammals in which the armor plating is composed of separate shields and hinged bands. But the related species of one extinct group, the glyptodonts, had a single-piece carapace similar to that of tortoises. These glyptodonts, some of which were as big as a Volkswagen and armored like a tank, survived up until quite recent times and may have been hunted by primitive Indian tribes; piles of glyptodont bones have been found alongside various human artifacts.

A few of the animals that had evolved in South America migrated in the reverse direction, becoming established in North as well as South America: the anteater, porcupine, opossum and armadillo. South America provides a spectacular example of how evolution can take off in novel directions when a region is isolated for a long enough period of time.

It also provides a dramatic lesson in how apparently well adapted species can often be driven to extinction when exotic species those coming from outside are introduced. The mammalian fauna of Australia also evolved in isolation since the early Cenozoic Eocene , but in this case the isolation remained complete.

For unknown reasons, Australia was apparently originally populated entirely by marsupials rather than placental mammals. Today the native mammalian fauna of Australia is made up of marsupials of many different kinds, that occupy ecological niches similar to those occupied by placental mammals in other parts of the world.

Evolution produced marsupial mice, a marsupial mole, and, most impressive, a marsupial wolf almost extinct and a marsupial lion extinct , all of which bear striking resemblances to the corresponding placental forms. Other Australian marsupials occupy the same ecological niches as certain placental mammals in other continents, but are rather different in appearance. For example the wallabies and kangaroos occupy the niche of browsing and grazing mammals which is occupied by the ungulates hoofed mammals in other parts of the world.

The Koala, a tree-climbing, slow-moving herbivore, occupies the same niche as the tree sloths of South America. The Koala is now being considered for Endangered Species listing in this country; its population has plummeted because of destruction of eucalyptus forests in Australia. Around Christmas over fires, most deliberately set, burned 1. Thousands of koalas were lost out of less than , remaining. Australia did produce some giant forms such as giant kangaroos, which are now extinct.

The Pleistocene is the time when humans evolved in the old world. The first hominids i. These called Australopithecus lived in Africa. They had a protruding jaw, prominent eyebrow ridges and a small braincase.

They walked upright. They made sophisticated stone hand-axes with sharp edges, possibly made spear points, and probably used fire. They spread over Africa and Asia and survived until about , years ago. The first fossils that are classified in the modern species Homo sapiens date from about , years ago Nat. By the end of the Cretaceous, flowering plants had become dominant, providing food for burgeoning populations of insects, which in turn became another high-quality food source for the mammals, along with fruits and berries.

New kinds of forests appeared, offering novel habitats for what would become tree-dwelling mammals -- primates, which first appeared about 50 million years ago, and eventually, some 45 million years later, upright-walking hominids, including us. The astonishing diversity of mammalian species today stems in part from the continuing breakup of the continents that began some million years ago and sent different landmasses moving apart. Australia and South America were isolated from other continents during much of the Tertiary, and marsupial mammals thrived and diversified there, while placental mammals took over similar roles on the other continents.

The story of the mammals is only one example of adaptive radiation, a process that has happened again and again, at scales both large and small, in evolutionary history. The Rise of Mammals:. Although they came into their own only after the extinction of the dinosaurs some 65 million years ago, mammals had maintained a low-profile existence for some million years before that. Web Activities.