Why Are We Not Immortal? Poem by Paul Hartal

He examined her with keen interest.
There was a short spell before he posed the question:
"So, do you believe that your DNA is the same as mine? "

"No", she said.

"I am surprised to hear this", he said.

"Why? " she asked. "Nature abhors uniformity.
But the main thing is that, unlike mainstream biology,
I believe that the DNA in every organism
is different. Actually, the full DNA sequence
in the cells undergoes changes in time.
Thus, the chromosomes become shorter and shorter
with each duplication process.
This leads to the eventual death of every individual.
The so called Hayflick limit is relevant here.
It was in 1961 that Leonard Hayflick
and Paul Moorhead discovered
that normal human cells can divide
only about 50 times in order to renew themselves."

"But life transcends human cell life", he objected.

"Still, the Hayflick limit appears to be
a comprehensive law", she said.
"Take, for instance, mice.These small rodents,
with an average life span of three years,
have a limit of 15 cell divisions;
whereas for Galapagos tortoise, which can live
for 175 years, the boundary is 110 divisions.
Of course, the tortoise lives longer
than mice and man, but it still dies.
Now, the key to what happens in all these cases
and elsewhere involves the telomere,
the end part of the chromosome
with its repeating DNA code
sequences. For in each cell division the telomere
looses a segment from the chromosome's edge,
until the Hayflick limit is exhausted and
cell replication comes to an end."

"Even so, I still think you oversimplify
the problem", he said. "And so,
the question of immortality remains
an unsolved biological enigma
and a puzzling mystery of life."