Grasslands thrived after the dinosaur era.
Dinosaurs were the dominant species on Earth until about 65 million years ago. At this time, a mass extinction occurred across the planet. It is believed a large mass impacted Earth, causing half of all living things to die. Many kinds of new organisms appeared after this event. The ones that took center stage were mammals. Before the dinosaur extinction, mammals were mainly small, nocturnal creatures, but afterward, these animals came out of the shadows and began to diversify.
Grasses
One kind of plant that thrived after the dinosaur era was grass. Grasses diversified on Earth about 54 million years ago. Today, more than 10,000 species of grass thrive on Earth. These plants quickly spread, forming savannas and prairies. No one is sure why grasslands begin to thrive, but scientists do know that Earth's climate had changed. Some think that, after the extinction event, Earth had drier weather. Others believe that Earth's carbon dioxide levels fell. Regardless, grass evolved by converting sunlight and nutrients in a more efficient manner. The explosion of grasses like wheat, rice and millet as well as forage grasses helped other mammals evolve after the dinosaur era.
The Age of Mammals
Without dinosaurs, there was a huge niche available for life. Mammals took over after the dinosaur era. Early relatives of primates, carnivores and herbivores appeared in the Paleocene era 65 million years ago. The first large mammal in this time period was the size of a pony and was called Pantolambda. After the Paleocene era came the Eocene era, beginning 55 million years ago. During this time period, herbivores diversified. First, odd-toed herbivores --- forerunners to horses --- appeared. After that came even-toed herbivores, forerunners to camels. Late-comers on the scene in Earth's long history finally appeared. The first apes evolved in the Miocene epoch, about 23 million years ago.
Whales
Ten million years after the dinosaurs, during the Eocene era, a land carnivore returned to the ocean. This carnivore was similar to the wolf, and its remains are found in modern day Pakistan. This animal had legs and spent some time on land, but was a forerunner of the modern-day whale. Fast forward 15 million years, and a fully aquatic whale called the Basilosaurus was on the scene. It still had small hind legs, though it could not walk. This ancient whale is now extinct. Current whales include toothed and baleen whales.
Homo Sapiens
Bipedal human ancestors appeared on Earth about 3 million years ago. The famous fossil "Lucy" is one of modern human's most recent ancestors, and was found in modern-day Ethiopia. Man is one of the most adaptable living organisms to ever evolve on Earth. Homo sapiens or modern humans are extremely new when compared with other living things on Earth. They evolved in Africa 200,000 years ago, and were hunters and gatherers. The skeletons of our direct ancestors were a much lighter build than the skeletons of other indirect ancestors. The first homo sapiens had large brains, small jaws and smaller teeth than any ancestor before.
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