Final answer:
Life expectancy in pre-flood societies was low due to high risks of injury and infection, with an average age of about 25 years. Agriculture provided some stability, but life remained precarious without modern medicine. Early civilizations faced numerous challenges but began to adapt and improve living conditions slightly.
Step-by-step explanation:
Before the advent of agriculture and modern medicine, life expectancy in the pre-flood or Paleolithic eras was considerably shorter than it is today. People led a nomadic lifestyle that involved hunting and gathering, which exposed them to various hazards such as injuries from hunting and infections from untreated wounds. Without access to medical innovations like antibiotics and surgery, even minor injuries could be fatal. The average age in these primeval populations was typically around 25 years. In addition to personal risks, early human settlements confronted challenges like unpredictable flooding and the necessity of constant labor for agriculture as seen in early civilizations such as Mesopotamia.
With the onset of agriculture and settled village life, there were biological advantages despite the increase in parasitic diseases. Life in small villages created some social hierarchies and protection from external threats as evidenced by the construction of walls around Neolithic villages. Over time, as people settled and developed technologies, life expectancy increased slightly but was still limited by the absence of modern medical care and the heavy burden of disease and hard labor.