The taxonomic order of Cetacea is comprised of around 75 mammalian species that evolved from ungulates over 50 million years ago (Wursig, 1989). Cetaceans encompass marine mammals including whales, dolphins, and porpoises. These distinct species demonstrate millions of years of evolution, having undergone incredible anatomical adaptations that would pave the way to the success of marine mammals. The Ungulates lost hind limbs, gained tails specific for propulsion, developed streamline bodies with modified fatty tissue called blubber for insulation replacing hair. Blubber allows large cetaceans such as whales, to store energy supplies for long migrations away from feeding grounds (Wursig, 1989).
Two suborders, the mysticetes or baleen whales and the odontocetes, toothed whales compose the order Cetacea. These two suborders are descendants of a common ancestral group, the archaeocetes. In baleen whales, long keratinous plates of ectodermal origin hang from their upper jaws replacing teeth entirely. These whales, filter invertebrates and small fish from water in through their large mouths. The larger filtering technique allowed efficiency in capturing and retaining a large amount of prey once (Wursig, 1989). Baleen whales also evolved disproportionately large bodies. This adaptation allowed the mammal to withstand seasonal migrations to areas with surpluses of food and, have the ability to fast for prolonged periods of time while reproducing (Wursig, 1989).
Toothed whales evolved elaborate echolocation. Rapid sequences of high-frequency clicks are transmitted into the environment and the whale listens for the return of the echo analyzing any modification in the sound. This allows the whales to distinguish shapes, sizes, textures and distances of objects in the water. This adaptation allowed odontocetes to expand their habitat and expand to all ocean basins, and many major rivers (Wursig, 1989).
Cetacean anatomy and physiology also changed drastically in order to adapt to sea life. The kidney increased its capacity for ionic concentrations of solutes by compartmentalizing renal units and increasing the total surface area in which ions can be transferred. Cetaceans also have high concentrations of hemoglobin allowing for large amounts of oxygen to be stored. Cetaceans soft body and skeleton also allowed for propulsion in a dense water environment, sustained breath holding, storage of energy and temperature regulation were also important features for success in marine life (Wursig, 1989).
Fossils are studied in order to understand the long history of life. Fossils allow the current environment of the planet, the rich diversity of organisms and the many different habitats in evolutionary and geological context (Liberman and Kaelser, 2010). Fossils are classified as any relic more than 10,000 years old. The original material of the organism has been substituted or infiltrated by a mineral and an imprint is left in the rock. The hard parts of organisms have the greatest chance of being preserved. These parts include teeth, bones, and shells, however, ice or amber can also fossilize and preserve organisms (Dawkins, 2004). When fossils were first discovered, the ages of the fossils mapped were unknown. The Law of superposition was used in order to rank how young or how old the fossil was. The younger strata would lie on top of the older ones unless there were circumstances in which the rock was out of order. These circumstances may include the deposit of rock by a glacier. However, by comparing equivalent rock layers in other parts of the world, these anomalies are corrected. In any one location, it is likely no sedimentary rock or fossils are being laid down. Therefore, paleontologists that study fossils must take into account they must look at different sites around the world in order to uncover fossils (Dawkins, 2004).
In particular strata, there is recognizable rock characteristics and properties that house the same kinds of fossils in different regions of the world. For example, the Devonian rock found in the county of Devon is also found in various parts of the British Isles, Germany, Greenland and North America( Dawkins, 2004). Devonian rock strata are recognizable by the quality of the rock but also by the fossils in which the rock contains. This occurs with other geological periods and eras from the Cambrian to the present Holocene. Relative dating is possible by piecing the fossils in chronological order based on the rock they are found in. However, absolute dating is possible through the physics of radioactivity (Dawkins, 2004).
Absolute dating is a process used to determine the age of fossils and it provides a numerical age or range in contrast to relative dating which places the events in order without any age between them. The primary methods of absolute dating involve radiometric dating, the radioactive decay of isotopes of elements trapped in rocks or minerals. One example of Radiometric dating is Radiocarbon dating. Radiocarbon dating is one of the most widely used of absolute dating. This is used to date organic remains. Carbon 14 is produced by the cosmic radiation entering the atmosphere of Earth. Plants then absorb the carbon 14 and move up the food chain as animals eat the plants and predators eat prey. The half-life of carbon-14 is 5,730 years. After an organism’s death, the carbon-14 uptake stops. Therefore, by measuring the amount of carbon-14 in organic material, scientists can determine the date of death. Other forms of dating such as potassium-argon dating can be used for older fossils over a billion years old (Milton, 2017).
Although fossils are very useful for understanding evolutionary past, the fossil record could be a big gap and the evidence for evolution would be supported (Dawkins, 2004). DNA information is in all living creatures and is handed down for hundreds of millions of generations. The information is duplicated, it acts as a historical record that renews itself with precise accuracy. DNA is comprised of four letters, A, C, T and G. The letters form three letter codons which code for biological amino acids. By comparing the protein or DNA sequences of modern animals, their relative relation can be established. Very close relations, such as humans and chimpanzees have more DNA in common than humans and bacteria (Dawkins, 2004).
The purpose of this study was to analyze given information and conclude whale’s evolutionary ancestors. It was hypothesized whales evolved from land mammals, specifically artiodactyl ungulates. In order to establish this relationship, the Eocene fossil record of Whales was organized in chronological order, the differences in the ear structures of land mammals to early whales to modern whales were observed, and finally, ankle bones of early whales and land mammals were compared.