why dogs don't live as long

Why dogs don't live as long as humans ..I thought this was very sweet:wub:

Being a veterinarian, I had been called to examine a ten-year-old Irish
Wolfhound named Belker. The dog's owners, Ron, his wife, Lisa, and their
little boy, Shane, were all very attached to Belker and they were hoping
for a miracle.

I examined Belker and found he was dying of cancer. I told the family
there were no miracles left for Belker, and offered to perform the
euthanasia procedure for the old dog in their home. As we made
arrangements, Ron and Lisa told me they thought it would be good for the
four-year-old Shane to observe the procedure. They felt as though Shane
might learn something from the experience.

The next day, I felt the familiar catch in my throat as Belker's family
surrounded him. Shane seemed so calm, petting the old dog for the last
time, that I wondered if he understood what was going on. Within a few
minutes, Belker slipped peacefully away. The little boy seemed to accept
Belker's transition without any difficulty or confusion.

We sat together for a while after Belker's death, wondering aloud about
the sad fact that animal lives are shorter than human lives. Shane, who
had been listening quietly, piped up, "I know why."

Startled, we all turned to him. What came out of his mouth next stunned
me. I'd never heard a more comforting explanation.

He said, "People are born so that they can learn how to live a good life
-- like loving everybody all the time and being nice, right?" The
four-year-old continued, "Well, dogs already know how to do that, so
they don't have to stay as long."