One old soldier in some country, who fought in the World War Second told me that his country was military nation、and most young men of his country passed away for entry into war. Where I live, in Japan, during war, children were told that their lives continued until around 20 years old for war, because population in the country were reducing for the number of death for war. However, if I had the chance to mention reasons why people are living longer now, I would say that progress of medicine and improvement of provision of food contribute to it.
   My primary reason is that progress of medicine prevents people from becoming serious diseases or death. One example of this is that in the past, there were not enough treatment and medicine for many diseases unlike modern medical circumstances. Quite a few people are going to die for diseases such as pneumonia: but modern medicine is capable of treating such a disease with modern treatment. However, I do not think that reduction of number of war or armed conflict contribute to human's longivity mainly. Surely World War Second broke out in last century, but in long history of mankind, worldwide war such as World War Scond rarely broke out: that is, reduction of population is temporary and partial.
 Another reason is that improvement of provision of food keeps health of people. For example, in old days, when there were not enough food for people, some passed away for inanition. The number of death for inanition is many, so that eating food is said to be even treatment for diseases those days. However, at the present day, when enough foods are provided for us, few people suffers from inanition except for economically poor countries such as countries in Aflica. The reduction of war, on the contrary, contribute to human's longevity only partly. For instance, during hostility between some country, they are not willing to trade; food which should be imported might not become avairable for economic sanction. However, the circumstance continues only during hostility, so that I scarcely think that reduction of war have influence on human's longevity.
 Therefore, I think that medicine and food are the most important for our longevity. As I see it, healty elements such as progress of medicine and improvement of provision of food are involved in why people are living longer.