down," said Rhys.

"Like the heart you mean?"

"Yeah," said Rhys, "It stops beating, or the kidneys pack up, or something else. If we could keep sticking new bits in, we'd live for a lot longer."

"Its like we're programmed to die isn't it."

"Must be," said Rhys, "Its funny isn't it. We can get new arms and legs fitted, and a new heart, and organ transplants, and just about everything replaced, but we can't get a new brain put in."

"So we'd end up with an everlasting body, and a head full of useless mush, wouldn't we. Ten thousand year old and as nutty as fruit cakes!" I said, "What a joke!"

Rhys thought it was funny too.

"But why do we die anyway?"

"We have to."

"Yeah, but why? Its not logical."

"How do you mean?" said Rhys.

"Well," I said, "Old Mac (that's our science teacher) told us everything works on the survival of the fittest principle. If something's bigger and stronger than something else, it will beat all the small, weak ones. So, if something lives longer, it has a better chance of surviving, so, why don't we live longer?"

"What about sabre tooth tigers?" said Rhys, "They should have survived. They had better teeth than lions."

"And stupid little mice, how come they're still around?"

"And wood lice" added Rhys.

"Sounds like survival of the luckiest to me!" I said. And that was as far as we got, because we just didn't know enough science stuff to talk about it. A few drops of clear water spattered on the concrete and the wind dropped. It was going to rain.

"Did you see the satellite coming in last night?" Rhys asked.

"No, I was watching TV," I said.

"I saw it," said Rhys, "It wasn't much, just a streak of light. It was burning up as it came in."