Fossil remains can be in the form of bones, found either in skeletons or separately; footprints in rock; impressions of skin, also in rock; and eggs. Most of the dinosaur specimens that have been collected are in museums. But at Dinosaur National Monument, near Vernal, Utah, a museum has been built around rocks holding dinosaur bones. (Weishampel, p.1)
The disappearance of the dinosaurs is in some ways a great mystery. During the time the dinosaurs lived, many new kinds developed and other older kinds died out. Not all kinds died out at once, but by the end of the Cretaceous period, the last of the dinosaurs had disappeared. Scientists have proposed several theories to explain the disappearance of the dinosaurs. There are two main theories of Dinosaur extinction as follows:
In 1980 the asteroid theory was proposed by Luis and Walter Alvarez. This theory is based on the discovery of unusually high concentrations of the rare metal iridium at rock levels close to the level of the last dinosaur remains. Iridium is more common in meteorites than in rocks found in the earth's crust.
According to this theory, a large asteroid crashed into the earth about the time the dinosaurs disappeared. The force of the collision caused a huge cloud of dust to circle the earth. The dust blocked the sun's light for as long as five years. This killed many plants, and without food, the dinosaurs died too.
High concentrations of the rare-e...
Alvarez's theory was further bolstered when, in 1990, geologists discovered a possible site for an extinction-level impact, a 200 km wide crater in southern Mexico. (Ron, p. 277-279)
2. Male Domination Theory
Miller et al. who were experts in the field of chemical engineering presented this theory and concluded that main reason of dinosaur extinction was the exceeded birth rate of males as a result of some specific climatic variation. It was a condition where under the gender of the brood was an outcome of temperature. This theory does not raise any criticism against other theories of dinosaur extinction. They don't oppose the idea that the stroke of meteorite upon the planet and its responding impacts in the long run to kill dinosaurs, but further elaborate it. They elucidate that among mammals like human beings and other creatures gender is genetically determined in an equal ratio. Whereas, in some cold blooded animals like fish and reptiles, sex determination is based on condition of temperature. If these conditions remain ideal, the male/female ratio can be 1:1. However, changing conditions of temperature may cause a slant towards either of the two genders. Consequently, a slant is towards males may direct a turn down in overall population. They further explain that this mechanism of gender classification is being even presently observed among the crocodiles which are basically alike dinosaurs in terms of both biology and physiology. Thus the idea of dinosaur this way is strengthened.
In order to demonstrate the impacts of gender ratio on overall population, the theorists utilized the idea of the "Evolution of Y Chromosome" in mankind and linked it with mathematical techniques. Moreover, even better representation is being proposed toward the