Evolution of Dolphins
Joseph Castaneda
Miami High School
Abstract Over 50 million years ago, the creature that we know as the dolphin today was a land based animal. It would venture into the sea, or water to eat. Over time though the evolutionary process would see to it that this once land based creature would become a part of the water, evolving in such a way that it would never again see the land. Along the way there have been numerous changes that have taken place to the animals physiological make-up as well as its mental capacities. It is almost magical the way this process has taken place, the way an animal can change and adapt to ensure its ultimate survival. In this paper I 'll be exploring both how and why this process has taken place, as well as other factors related to this amazing creature.
Dolphins are marine mammals that are closely related to whales and porpoises. They vary in size from 1.2 meters (Maui 's dolphin), up to 9.5 meters (the orca or killer whale); part of the largest family in the Cetacean order, the Delphinidae , dolphins have evolved relatively recently, about ten million years ago, during the Miocene. There has been a trend within mammalian evolution towards colonization of land, however in some instances this trend has been reversed; there are three large orders of mammals that have separately re-adapted to marine life, the Cetacea (whales, dolphins and porpoises), the Pinnipedia (seals, sea lions and walruses), and the Sirenia (dugongs, sea cows and manatees). This “re-adaptation” is most extreme in the cetaceans which have evolved a totally fish-like form, masking their true mammalian ancestry (Coffey, 1977). The evolution of cetaceans is so well documented, and is considered one of the best examples of macroevolution, as documented by fossils (Thewissen &Williams, 2002), that is has become known as the Rosetta stone to evolution itself. The most primitive ancestor of cetaceans in fact looked
Miami High School
Abstract Over 50 million years ago, the creature that we know as the dolphin today was a land based animal. It would venture into the sea, or water to eat. Over time though the evolutionary process would see to it that this once land based creature would become a part of the water, evolving in such a way that it would never again see the land. Along the way there have been numerous changes that have taken place to the animals physiological make-up as well as its mental capacities. It is almost magical the way this process has taken place, the way an animal can change and adapt to ensure its ultimate survival. In this paper I 'll be exploring both how and why this process has taken place, as well as other factors related to this amazing creature.
Dolphins are marine mammals that are closely related to whales and porpoises. They vary in size from 1.2 meters (Maui 's dolphin), up to 9.5 meters (the orca or killer whale); part of the largest family in the Cetacean order, the Delphinidae , dolphins have evolved relatively recently, about ten million years ago, during the Miocene. There has been a trend within mammalian evolution towards colonization of land, however in some instances this trend has been reversed; there are three large orders of mammals that have separately re-adapted to marine life, the Cetacea (whales, dolphins and porpoises), the Pinnipedia (seals, sea lions and walruses), and the Sirenia (dugongs, sea cows and manatees). This “re-adaptation” is most extreme in the cetaceans which have evolved a totally fish-like form, masking their true mammalian ancestry (Coffey, 1977). The evolution of cetaceans is so well documented, and is considered one of the best examples of macroevolution, as documented by fossils (Thewissen &Williams, 2002), that is has become known as the Rosetta stone to evolution itself. The most primitive ancestor of cetaceans in fact looked
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