In general， people are living longer now. Discuss the causes of this phenomenon.
论点： 没有结论，不可知，但是有各种说法
1. 个人因素： 饮食，环境，医疗， 体育锻炼
2. 家庭因素： 遗传的争议
3. 社会因素： 整体生活水平和医疗水平，社会的价值和美学体系
4. 未知的神秘两难： 人必死，人要生
Human life spanorlongevity has been presumably claimed to be longer than it was. Nevertheless， no verified statistics are available to support this assumption. Although many theories have been put forward to shed lights on the mystery of human aging， debility， and death， the correlation between longevity and a factorora series of factors is yet spurious.
In the ancient times， human life span was deemed to be determined by unknown force， whose name varied from religion to religion and from culture to culture. In ancient China， it was considered to be totally doomedorpredestined. The force was called Tian Ming. Tian means the heaven， similar to the Father in Heaven in Christian religion， while Ming implies fate. Hellenistic culture and Egyptian civilization have similar counterparts but in different versions.
In the modern time， nevertheless， science and technology have not only dominated human material world but also exerted tremendous influences on mentalorspiritual world， eroding the primitive faith and beliefs about human life and longevity. But scientists have never reached a conclusive agreement about the determinant of human life span. Some scientists attempt to reveal this millennium myth by conducting research on the process of aging. They assume that human life span is genetically determined. That is to say human genes contain a program that determines the life span. Nevertheless， the correlation between gene and life span remains to be a myth. In this case， what the scientists have undertaken is nothing but to create more myths because they first have to understand what gene is and then they must unambiguously explain what the program is and who creates the program in gene. Alas!
Some scholars even argue that the modern medicine and advanced medical care programs， together with healthier foods and scientific eating habits， have contributed to the assumed longer human life span. They， however， have failed to see that in many cases it was just these modern medicineormedical care programs that account for why people today have more lethalorpestilential diseases such as the highly contagious respiratory illness appeared in 2002 called SARS . The use of antibiotics is also believed to be the direct cause of some new virus such as the corona virus in the SARS case.
As to the foods， it is hard to believe that they are healthier. In fact many crops， vegetables， fruits， and animals have been formidably polluted in the process of growing by pesticides， herbicides， and chemical fertilizers. Therefore， it is arbitrary to say that healthier foods help people live longer. In addition， the prevailing eating habitsorlife styles might be scientific because they are heavily influencedoraffected by scientists and their cheap products. But it is invalid to claim that scientific life style naturally leads to longer life span. Neither convincing scientific theories nor empirical evidence show that foods and the way people eat contribute to the extension of human life span.
To summarize， no verified evidence demonstrates that human life span today is longer than it was， in statistic sense， since it is impossible to compare the life span of an individual to hisorher otherwise life span. Moreover， the factors contributing to human life spanorlongevity are too complex to know yet.