Instructions: The draft literature review below is much like the egg primacy example in Chapter 4. Take a few moments to draft a good revision, then a better revision, of this literature review. As before, all citations and claims are entirely fictitious.
Another Sample Lit Review
Other scholars reject the egg primacy argument in favor of claims that chickens preceded eggs on the evolutionary tree. Webster (1988) argues forcefully in the Journal of Evolutionary Theory Studies (JETS) that chickens could have preceded eggs if the evolution to egg production resulted from a genetic mutation induced by strong and sustained electromagnetic pulses. The most likely source of such pulses, he argues, is “concerted and sustained attacks on Planet Earth [sic] by non-native life forms.” These life forms, he suggests, are “what are most commonly called aliens by the lay public” (385), though he refuses to speculate on their origin or their means of arrival (391). JETS is a highly respected publication with a journal impact factor of 1.7 (source: journal website), so we must take the claim – however ludicrous it seems to me – at least a little bit seriously.
On the other hand, Nicholson (1990) argues in the same journal that electromagnetic pulses are unnecessary. He claims that solar radiation – either during periods of thinned ozone during the Snowball Earth period or from a hole in the ozone layer created by the end-Permian meteorite’s entry into Earth’s atmosphere – could have resulted in similar effects without the “slightly incredible” (Nicholson 1990, 838) assumption of alien or extraterrestrial warfare. Nicholson’s evidence, however, seems mostly correlational and conjectural; he presents no direct evidence proving either of his proposed causal mechanisms.
The JETS issue where Nicholson’s article appears also contains several rebuttals and counterarguments from other researchers. Webster (1990) attempts to rebut Nicholson’s claims, though he presents no new evidence in support of his own thesis aside from an article on the website of a group supporting the search for extraterrestrial life that suggests the Earth once was closer to a pulsar star.
The following article by Watkins and Jin (1990) conducts a thought experiment in which they analyze the chain of events leading from the electromagnetic pulses to the conversion of an existing species to an egg-laying type. While the overall process involves several steps, they believe that the most important is that the electromagnetic pulses would have had to induce multiple simultaneous (or nearly simultaneous) changes in chickens’ DNA, particularly those governing reproduction. They claim that this is unlikely for three reasons. First, electromagnetic pulses are not known to cause genetic mutation; in fact, scientists have demonstrated rather conclusively that electromagnetic exposure, even to pulses, has no discernible effect on DNA mutation rates (1013). Second, these changes would have had to occur both identically and simultaneously across many chickens to produce a transition to egg-laying across the population, even if the transition took several generations. Producing mutations, any particular mutation, and simultaneous mutation are all rare events, so the joint probability of all three is “exceedingly, almost impossibly, low” (1990, 1021). Third, they argue that the genes governing reproductive processes are among the most resistant to mutation because of their central role in species preservation. The net result of all of these rare events is that the probability of mass mutation to a novel reproductive system is virtually nil (Watkins and Jin 1990, 1023).
Other studies adopt a more anthropological approach. Ralph Loren, who is “professor emeritus at Princeton University” (Loren 1976, 25), analyzes the behavior of modern chickens to explain evolution. By studying Javanese Red chickens – the ancestor of all of today’s chicken breeds – Loren hopes to identify reasons why egg laying would be of particular reproductive and evolutionary value to chickens. He concludes that “the evolution of external reproduction techniques such as egg laying” (26) provided improved continuity of the species during a period in Javanese history in which crossing the road became substantially more dangerous. External reproduction, he notes, “allowed for surrogate mothering by other hens in the event of the untimely death of the laying hen” (28-29).
Finally, Hill’s (2002) book builds on the study of Javanese chickens by suggesting that egg formation was an evolutionary strategy to expand the flightless species’ range in an archipelagic region such as Indonesia. Chicken eggs float in salt water, and an egg is a self-contained embryo requiring no outside nourishment. The average temperature of the Indian Ocean in the region of Indonesia is between 72 and 82 degrees Fahrenheit, which would combine with reflected solar rays to provide sufficient warmth for the egg to incubate even without a mother chicken to sit on it. Oceanic currents would sweep eggs to other land masses, where the chicks can hatch and fend for themselves (Hill 2002, 49). Provided that both male- and female- containing eggs are equally likely to disperse and survive, or that a suitable other type of bird that can mate with chickens is available in the new location, the species can thus both perpetuate and spread across the islands and onto the Asian mainland without need for flight (Hill 2002, 282).
Jackman (2004) takes issue with Hill’s (2002) concluding assumptions, arguing that the difference in weights in hen and rooster embryos would make rooster survival of the dispersion process much less likely. He proceeds to demonstrate this with the use of very sophisticated statistical tests, including a “likelihood ratio test” that gives a p value of 0.000 (Jackman 2004, 118). He also emphasizes the values of the “cutpoints,” whose values are 12.803, 19.711, and 26.557 (2004, 120). Jackman thus concludes that Hill’s assumptions are “invalid” (2004, 123) and that his conclusions “should be discarded” (2004, 124).