How do scientists believe the Iceman died?

Which statement best summarizes this excerpt from leo tolstoy's the death of ivan ilyich? and in imagination he began to recall the best moments of his pleasant life. but strange to say none of those best moments of his pleasant life now seemed at all what they had then seemed—none of them except the first recollections of childhood. there, in childhood, there had been something really pleasant with which it would be possible to live if it could return. but the child who had experienced that happiness existed no longer, it was like a reminiscence of somebody else.

In poem daffodils-how do we know that the yellow daffodils has a long lasting effect on the speaker.

What is the reasoning in this argument?