The Disappearance of Dinosaurs
The question of the disappearance of dinosaurs forms an interesting toping of discussion. Because of this, several theories have been formulated on how dinosaurs disappeared from the face of the earth and the implications of their disappearance. From theories on climatic changes to those of sudden impacts, the exact reason behind the extinction is still to be fully explained. The question thus remains to be answered. In order to find a comprehensive way of building up the solution to this question, the present research aims at finding out the theories that explain the disappearance of dinosaurs. Through a review of literature, it will be possible to understand various theories and to find how relevant they are to answering the question of what caused the disappearance of dinosaurs. While answering the research question may not help to fully comprehend the phenomenon behind the disappearance of dinosaurs, it may,provide differing viewpoints to the subject. The ability to compare different viewpoints will enable the reader to build an understanding of the underlying concept. Moreover, the study will contribute to the academic arena through the provision of comparative rather than suggestive information. While most of other studies on this subject have focused on providing information explaining how dinosaurs disappeared, the present study compares the already suggested theories.
Several theories have been suggested to have caused the disappearance of dinosaurs. In a literature review carried out by Russel (1979), the occurrence of terrestrial reptiles such as dinosaurs was correlated to the availability of high rainfall amounts and abundance of plant growth. From this correlation, it can be deduced that dinosaurs could exist more where there are such conditions and that the absence of such conditions could stifle the proliferation of such wildlife. According to the study by Russel, extinction of dinosaurs was accompanied by changes in the lithology of the land. This is further explained through the exemplification of deep ocean circulation changes which are suggested to have caused fluctuation as in the composition of the basinal carbonates. From the work by this author, the conclusion drawn is that the disappearance of dinosaurs could have been the result of lithological changes steered by compositional changes in deep-ocean conditions. This theory is comparable to that suggested by Krassilov in which vegetation changes are blamed for the disappearance of dinosaurs (1981). According to Krassilov, dinosaur communities were replaced due to vegetation changes, particularly the forestation which occurred at the end of the crustaceous time. The localities of dinosaur were in most cases situated in warm and warm temperate areas while only a few of them were found in the temperate areas due to the climate conditions therein.
While the two authors and many others propose climate and vegetation changes as the causes of dinosaur extinction, it cannot be exactly agreed that these were the actual causes of the same. This is based on the argument of Buffetaut (2004) who claims that long term changes in the climate especially in climatic cooling as well as other suggested vegetation change theories cannot be blamed for the extinction of dinosaurs. From the opinion of Buffetaut and based upon a review of relevant literature, a study of the remains of dinosaurs and the locations in which they were found compared to the times in which those remains were found shows that dinosaurs were capable of adapting to various climatic and vegetation conditions hence could not be made extinct by changes in such aspects. From the work of Sereno (1999), the extinction of dinosaurs can only be understood through an understanding of the evolution process which the reptiles underwent. As an explanation of this, Sereno suggests that geological evidence if followed, there are patterns of relationships that follow the breakup of the land masses. This implies that it may actually be this break up that resulted in the extinction of the dinosaurs rather than changes in land use and vegetation cover. The differentiation of the dinosaurs prior to their extinction is also said to result from changes in earth structure. Sereno concludes by asserting that the biography of the dinosaurs can be modeled by the extinction of regions as well as the intercontinental dispersal. To oppose the claim that contrary to the theories that climate and vegetation changes resulted in dinosaur extinction, Sheehan et al (1991) suggested that the extinction could only be understood through a study of the patterns of ecological diversity over a 3 year period. According to Sheehan et all, all evidence points towards the occurrence of an abrupt extinction event which could have been caused by abrupt activities such as an asteroid impact. This is also the theory postulated by the authors about the disappearance of the dinosaurs with claims that that extinction has nothing to do with gradual evolution or environmental impact.
The question for the research study was: What are the major theories explaining the disappearance of dinosaurs? From the review of various literatures provided it can be said that the theories explaining the disappearance of dinosaurs can be classified into two major segments. The first set of theories suggests the influence of climate related factors such as cooling conditions and vegetationchanges towards the evolution and subsequent extinction of dinosaurs. On the other hand, the second set of theories opposes the idea that environmental conditions could have led to the extinction of dinosaurs and that the extinction is more likely to have occurred through sudden events such as separation of land masses and meteorite impacts. The theories postulated by the authors of the reviewed materials contribute immensely to the present study in various ways.
First, the theories postulated by Russel (1979) and Krassilov (1981), have the function of giving the idea that dinosaurs were made extinct as a result of climatic changes and vegetation changes respectively. These two theories enable the disappearance of the dinosaurs to be considered as subject of study in connection with cross- temporal vegetation changes. From this point of view, it is also possible to consider changes in the climatic conditionswhich occurred over the years and to study the anatomy of physiology of the dinosaurs. It is believed that from this perspective, studies carried out in later years focused on relating the two aspects, something which did not exactly provide the required results. The consideration of dinosaurs as being capable of adapting to environmental conditionsclearly shows that the latter studies focused on finding the connection between dinosaurs and their environments. An understanding that dinosaur remains were found in regions of varied climatic conditions clearly shows that they were capable of adapting to the same. While the change in climatic conditions proves to be slightly off in explaining the disappearance of dinosaurs that of vegetation changes appears to be slightly convincing. However, a connection can still be made between the two. Dinosaurs may be adaptable to climatic conditions such as extreme cooling. However, if the plants they fed on were unable to survive in those extreme conditions, they could have probably died as a result of hunger rather than the coldness. Either way, the extinction could still be tied to the aspect of vegetation as well as to that of climatic changes.
On the other hand, the theories advanced by Sheehan et al (1991) and Sereno (1999) and which is supported by Buffetaut (2004) link the disappearance of dinosaurs to changes in the earth structure. These theories may be convincing but it is difficult to comprehend exactly how this occurred. For instance, it proves challenging to merely believe that dinosaurs could have been made extinct through a sudden event such as a meteorite impact (Sheehan et al., 1991). The reason why this is challenging is because for one, there were many other life forms prior to the events that led to the extinction of the dinosaurs. Most of those life forms are still in existence even after having gone through those factors mentioned by the impact theory. Secondly, in case there was such an event like a sudden impact that is claimed to have led to the extinction of dinosaurs, it could not have ended the lives of all dinosaurs at once since most of the research shows that the population of dinosaurs was spread across several geographical locations. The rationality of the possibility that a single impact could have led to the extinction of dinosaurs is thus questionable. Similarly, the idea that the separation of land masses could also have led to the extinction of dinosaurs as postulated by Sereno (1991) is also unbelievable. For instance, if the land masses separated, the dinosaurs could have been transferred to other locations or separated from each other rather than made completely extinct on a single event.
While the theories advanced aim at explaining the extinction of dinosaurs, their accomplishment in this regard is thus considered minimal. However, when it comes to the present study and the focus on the research question, the theories postulated by these authors are highly relevant as they provide the desired information. To effectively answer the question of what caused the disappearance of the dinosaurs, each of the obtained theories is limited in its own way. It is thus necessary to focus not only on the already postulated theories but on aspects far beyond the already available information.
The theories explaining the disappearance of dinosaurs have been effectively highlighted herein. Some of them such as the effects of adverse cooling climate as suggested by Russel (1979), the effects of vegetation changes given by Kassilov (1981), separation of the Pangaea (Sereno, 1999) and sudden impacts as postulated by Sheehan et al (1991) all contributed to the discussion above. From the results obtained, each of these theories, despite being relevant to the present research, is limited in its own way. Understanding what exactly caused the disappearance of dinosaurs thus requires greater analysis of the prevailing facts, a subject that cannot be explored within the scope of the present study. In conclusion, it would be necessary to dig deeper into available literature, to compare theories as well as to comprehend the underlying facts rather than merely speculating on them.
Buffetaut, E. (2004). ‘Polar Dinosaurs and the Question of Dinosaur Extinction: A Brief Review.’ Paleogeography, Paleoclimatology Palaeoecology, 214, 3, 225-231.
Krassilov, V.A. (1981). ‘Changes of Mesozoic Vegetation and the Extinction of Dinosaurs.’Paleogeography, Paleoclimatology Palaeoecology, 34, 207-224.
Russel, D.A. (1979). ‘The Enigma of the Extinction of the Dinosaurs.’Annual Review of Earth and Planetary Sciences, 7, 163-189.
Sereno, P. (1999). ‘The Evolution of Dinosaurs.’Science, 284.
Sheehan, P., Fastovsky, D., Hoffmann, R. and Gabriel, D. (1991). ‘Sudden Extinction of the Dinosaurs: Latest Cretaceous, Upper Great Plains, U.S.A. Science.’ Science, 254, 5033, 835 – 839.