Greetings, megabyte, and welcome to UM.
I echo the sentiments of others who have commented and must stress the fact that human lifespans are hardly static. In the Bronze Age, when the Sumerians, Akkadians, Egyptians, and others were honing the their creation myths, the average lifespan was approximately 35 years. Approximately thirty percent of all children died before their fifth year of life; 20% of all pregnancies ended in spontaneous miscarriage.
Today, on the other hand, the average lifespan (in the West, at least) is around 76 years. Further, the average human is significantly taller than his ancestor of some 3,000 years ago. Whereas most Westerners get married in their twenties and have children in their twenties or early thirties, in the Bronze Age a bride could be as young as twelve or thirteen years of age and her husband only a few years older. When you were eighteen years old and "middle-aged," you started a family by what we modern folks would consider to be extremely young--still kids, really.
A multiplicity of factors determine lifespan, and it's all well understood through scientific principles. Aliens are not needed. The most obvious factors are good nutrition and modern medicine. The absence of something so basic as vaccinations is one main reason the infant mortality rate in the ancient world was so universally high. And something many people don't realize is that one of the greatest inventions in all of human history was the capability to produce clean, safe drinking water; that alone lengthened average lifespans.
When trying to tackle these subjects in the course of one's studies, the critical factor is the quality of sources to which one turns. While there is an abundance of high-quality and reliable research material that is available to everyone, I cannot agree enough with something TheSearcher mentioned in the second post of this discussion: sources like
Ancient Aliens are not to be trusted. I've seen numerous episodes of this program, myself. TheSearcher said that when you watch this program, you must take it's information with "a big bag of salt." I might extend this analogy and suggest there is not a bag of salt in this world that's large enough. The information dispensed on
Ancient Aliens is so lacking in substance and scientific evaluation that, in my opinion, it has no research value whatsoever. In other words, you won't learn a single thing that's pertinent to real-world historical facts.
Finally, on the subject of aliens, I am not the least shy about stating my own opinion. I am absolutely certain that aliens had
nothing whatsoever to do with the developments of ancient cultures around the world. Indeed, these ancient societies did not need the assistance of aliens. This is the sort of thing of which TV shows like
Ancient Aliens are so unforgivably guilty: at the same time that they dispense oodles of intellectual flotsam, they rob ancient societies of the great things ancient peoples achieved. Give credit where credit is due.