Complex sentence: The average life expectancy of a human being in Satya yuga was mentioned as above 4000 years.During Satya Yuga all people engage only in good, sublime deeds.
Split into simpler sentences: The average life expectancy of a human being in Satya yuga was approximately 4000 years. Accordingly on the advent of the Satya yuga all people shall engage assiduously in good, sublime deeds.