Could anyone please kindly go over my essay and check if I have any stylistic/ grammar/ logic issues.??
As English is my second language, I think I may not be clear in my writing.,, but it is really hard for me to know how i can improve my writing style...

Any help/ comment would be greatly appreciated!

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<Prompt>
The following appeared as part of a letter to the editor of a scientific journal.

"A recent study of eighteen rhesus monkeys provides clues as to the effects of birth order on an individual's levels of stimulation. The study showed that in stimulating situations (such as an encounter with an unfamiliar monkey), firstborn infant monkeys produce up to twice as much of the hormone cortisol, which primes the body for increased activity levels, as do their younger siblings. Firstborn humans also produce relatively high levels of cortisol in stimulating situations (such as the return of a parent after an absence). The study also found that during pregnancy, first-time mother monkeys had higher levels of cortisol than did those who had had several offspring."

Write a response in which you discuss one or more alternative explanations that could rival the proposed explanation and explain how your explanation(s) can plausibly account for the facts presented in the argument.

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The author argues that individual’s birth order determines the levels of stimulation, based on the studies involving monkeys and humans. While the argument may seem plausible at first, it is rife with generalization, vagueness and assumptions, and thus lacks support to be sound enough; the mentioned study might not have representative samples, the conclusion is based on heterogenous subjects and situations, and the study may not have been controlled.

Firstly, the samples of the studies might not be representative of the population. In any studies, sample size and sample constitution can significantly influence the outcome. However, in his statement, the author falsely presumes that the sample size is large enough and the samples are representative of the population. Specifically, the study involving infant monkeys involved only eighteen subjects, a sample size much far from being sufficient.
Furthermore, sample sizes related to the infant humans and pregnant mothers are not even provided in the article, which further weakens the argument. In a similar line of reasoning, the author does not specify on what kind of monkeys were used as samples in the study, to preclude possibility of a biased sampling. What if the sample monkeys were constituted from those older than 1 years old? The results can vary greatly depending on the sample composition, and the samples might not be representative of the whole.

Secondly, the study wrongly draws a single conclusion, based on heterogenous species and situations without any justification. Although humans and primates share many common genetic traits, they are not an identical species. Thus, biological responses to stimuli can also vary greatly. To use human infants’ case as a supporting evidence, the author should have mentioned how the biological responses of humans relate to those of monkeys. However, in this case, drawing a single generalized conclusion based on the evidence of monkeys and humans does not seem adequate and only confounds his assertion. Furthermore, the stimulated situations monkeys and humans were faced with were very different; monkeys were encountered with an unfamiliar monkey and humans were faced with the return of a parent after an absence. Although one can concede vagueness of the situations is justified, it is not justified to draw a simple generalization based on the study with such heterogenous conditions and components.

Lastly, even if above points happened to play in the author's favor, the argument still depends on a presumption that the study is well controlled. The author does not specify on the situation and subjects, which leaves room for the possibility that the study may not be controlled. For example, if the first-born monkeys had been older than second-born when observed, and there had been few older monkeys in the community who can help them, they would have felt a much stronger responsibility to protect his group and thus would have exhibited higher stress and higher cortisol level, while younger ones feel protected. However, it is not certain as to whether second-born monkeys will experience the same amount of stress once they reach the same age and are then put in the exactly same situation as the first-born without such protection.

In conclusion, in its current form, the claim seems to lack support, and further concrete evidences pertaining to the authors assumptions on sample size and characteristics, heterogenous subjects and situations, and whether control of the study would have to be provided to determine the validity of the claim.