In an imaginary planetary system, the central star has the same mass as our sun, but is much brighter so that only a planet twice the distance between the earth and the sun can support life. Assuming biological evolution (including ageing process etc.) on that planet similar to ours, what would be the average life-span of "human" on that planet in terms of its natural year? The average life span of a human on the earth may be taken to be 70 years.