Why is human life decreasing from generation to generation?

I argue that human life is decreasing from generation to generation. In my first digit years of age before forty years, I used to observe many people living from eighty up to hundred years. I had also been told by my parent that two to three generations before this generation, people were used to live even longer life up to fifty years.

Currently, although life expectancy vary depending on various factors such as race, life style location, wealth, culture, etc, it is rare that the average age of man exceed eighty years. Why is it?

Evolution may have its own impact to make man delicate, week and non resistant fastening her/his death but the main reason is technology. Environmental pollution, global warming, deforestation, etc, are factors brought about by technology contributing for a shorten life. Fertilizers, vehicles as transport, industrial food products, etc, are another factors reducing human life.

In short, although technologies such as medication, pharmaceuticals, etc, increase human life, its negative impact upon human life outweighs its positive impact.