One of the changes brought about in the 21 century is yhe the extended life expectancy, likewise, there's there has been a lot of accounts and debates as to the cause of this phenomenon. Some may argue that it's because of the way people live, with more comfortable houses and conditions. While it's it is true, I believe a more convincing answer can be found in mainly the advancement of medication and agriculture.
To start with, it's no secret that people long time ago used to get killed by what is considered as a minor symptom from today's standards such as malaria or food poisoning. With the advent of vaccines and a numerous preventative medications, we now can can now deal with those, once considered to be lethal, with ease. One promising evidence can be seen from the epidemic that was swiping swiped across Europe in during the Middle Ages, which killed killing one third of the population. [Also, it's it is widely known that the very cause of killing the death of thousands of natives Americans upon the Europeans first encounter with them is their lack of immune immunity to those diseases brought about by Europeans at that time, which,of course, is treatable easily easily treatable with a help of the development of vaccines.] (문장의 길이가 너무 길어져서 뜻을 이해하는데 어려워 집니다) In our society, we are now heading to the extent where we can cure even cancers and AIDS. More and more people can be saved with our technology of medications, which was never thought of as possible before. [Therefore, the very reason why people live longer is because of the medications curing various kinds of sicknesse and diseases.] (마지막 문장에 나오는 내용이 문단 전체의 내용과 별개 입니다. 단순히 약물의 존재 때문에 더 오래 사는것이 아니라 약물의 '발달' 때문에 더 오래 사는것이 아닌가 싶습니다.)
Moreover, every countries country might have had one or more times in their history when a lot of people died of hunger starvation. For instance, in the early 1950's, there was a time what is called the "tough hill in Korea." from which more than 2 million people died of due to the lack of food. This very phenomenon was caused by failure of that year's crop harvest. Seen from this experience, whether or not a certain time's harvest failure can put a thousands and millions of people's live in jeopardy was common even until recently. After the Industrial Revolution, the demand on of food skyrocketed like at an unprecedented rate, thus the competition(어떤 competition이요?) mounted up. Companies tried to come up with ways to make mass production produce of crops and meat possible,which, gradually, led to the development of some [sorts](sorts가 무엇을 설명하는거죠?). With more food available [with much faster productivity](생략 하시는 편이 나을것 같습니다), more people can be fed, [which is the main source of life in the very first place.](생략)
[Thanks to all the people who tried hard to invest and invent variety of medication and treatment, equal thanks to all those involved in making mass production of food possible. We now can enjoy not only much healthy life but also longer life on account of these people and the result of their hard work.] (문단 전체가 문법적으로 어색합니다. 의도적으로 글에 색을 부여하기 위해서 스타일을 집어 넣으신것 같은데, 오히려 역효과가 일어나고 있습니다.)
-에쎄이를 쓰실때에는 it's, he's, they're 와 같은 표현을 쓰는 것은 좋지 않습니다. it is, he is, they are으로 다 풀어서 쓰시기 바랍니다.
-항상 애매모호함을 없애기 위해 신경 써주세요.