QUESTION: 1.Why was life span longer in the beginning of human species, shorter in the Middle Ages,seems to be increasing in the 21stCentury, and expected to be longer in the near future?
2.As an anthropologist, how do account for the origin of human species, decline, and death? Are there some forces behind, if yes, what are the force?
ANSWER: Hi Evaristus,
I don't think that life spans were all that long in prehistory. There may have been some individuals who may have lived a bit longer but life expectancy in prehistory was relatively short. You were an old man if you reached 40. A hunter gatherer or early farmer life style was harsh and brutal. During the so called Middle Ages, living in cities with rampant diseases and squalor, life expectancies were even shorter. Some, again lived longer but may have been able to avoid the diseases that rampaged through the cities of the time like Small Pox, Cholera, Typhus etc... With the advent of modern medicine and antibiotics life expectancies have increased dramatically. We no longer die of Small Pox, Cholera, Measles etc... More of us live in to old age. As modern science and medicine continue to find "cures" for a wide range of diseases, including cancer, our life expectancy will continue to rise.
Man, as with all other species of living organisms, evolved from earlier forms. Homo Sapien Sapien arose from Homo Erectus or perhaps Homo Sapien Neanderthals. We don't have a clear view as yet into our over all evolution. Climate change did have an impact I believe but in what way, I can not say. As for our decline? I'm not sure that we are in decline given our growing population. However, should the climate change abruptly as a result of our changing the environment, there may be a sudden decline in our population. If water resources continue to fail, we will see mass starvation, wars, etc.. Our cities are too densely packed and a new disease could evolve to which we have no immunity and this could kill millions in a matter of weeks or months. Much like the plague did to Middle Ages cities. It is estimated that more than 40% of the worlds population was wiped out by the plague (Black Death).
Ebola could be such a threat as could Marlberg Virus, or something unknown. The "Spanish Flu" or N1H1 virus could be deadly. Or the Earth could be struck by a large asteroid much like what killed off the dinosaurs 65 million years ago and that gave rise to Humans. WE humans are a rather fragile species and have only been around for 500,000 years give or take. The dinosaurs were around for millions of years in comparison. There may be other forces that could lead to the demise of our species that we aren't even aware of. But not to worry, chances are it won't
be in our life times or the life times of our children.
---------- FOLLOW-UP ----------
QUESTION: You made mention of Homo Sapien which arose from Homo Erectus or perhaps Homo Sapien Neanderthals in connection with evolution. Looking at the evolution of human Species, which one is first, Man or Woman? Where did evolution of human Species started?
Evolution is a long slow process that can suddenly jump when the right genetic mutation occurs or when enough small changes occur over time. These changes can be good or bad. For instance there is a genetic mutation called sickle cell anemia. Those who have it can live with malaria more effectively than those with out the mutation. However, when malaria is not endemic to where people live with the mutation, life is hard.
As for which was first, no one knows. We have been looking at the DNA of both the Y chromosome and the mitochondrial DNA ( from the female side), to see if something can be determined, but thus far nothing.
Mans evolution started millions of years ago and survived the asteroid which destroyed the dinosaurs. At the time only primatives mammals were living but they somehow survived the extinction event. These early mammals evolved over time to start the primates which evolved over time to Australopithicus an early bipedal creature, they then evolved further into early Hominids from which we arose. We don't know where the first of our species lived, probably in Africa, and we spread out over the whole of the Earth. This also took time and evolution didn't stop there.
Who came first, man or woman. Probably woman, but this is not known with certainty. Mitochondrial DNA comes from the X chromasome. In the third paragraph above when I speak of "man" it in the generic sense including both men and women. Homo Sapien Sapien only evolved perhaps 500,000 years ago but the fossil record is incomplete.