I don't spend a lot of time in the back seat of our Toyota SUV. Usually, I'm in the driver's seat, the daddy position.

But on a recent trip to a Knoxville-area family reunion, I found myself sharing the back seat with my 6-year-old son and a hyper puppy.

Our mixed-breed pup, Boise, decided the three-hour car trip would be a good time to go wild. This is the same dog who leaps at the TV when the animated shrimp start talking in the movie "Shark's Tale."

So to keep Boise from jumping onto the steering wheel and sending us careening down an embankment, my wife and I took turns holding him in our laps.

This gave me some uninterrupted time with my younger son, who is a chatterbox.

Late Saturday, we settled in to the last leg of our drive, having just stopped at a Walmart, where I had to step between our sons. The little one had grabbed a star fruit in the produce department and exhorted his 11-year-old brother to, "Go long!" (Among the things not covered in the Daddy Handbook is how to break up a football game at Walmart while the loss-prevention staff watches you on split-screen televisions.)

Later in the car, I looked over at my younger son in the back seat and he smiled.

"So, do you think any alligators will attack our house, Daddy?" he asked me nonchalantly.

"No, son, I don't think we have anything to worry about in that department," I said. "And anyway, we have a trusty dog and a steak knife to protect us."

"I killed an alligator with my bare hands once," he said, lifting his eyebrows and kicking his legs.

"You did?" I said, playing along.

"Yep, it was when I lived in a cabin by the ocean," he said. "It was before you knew me."

"OK," I said, "I wasn't aware you had a life before I knew you."

Trapped by his imagination, he paused for a second to think of his next line of questions.

"What states are below Tennessee?" he asked.

"Well, if you mean directly below Chattanooga, that would be Georgia," I explained. "Also, Alabama and Mississippi are technically 'under' Tennessee on the map."

"So, if I dig in the back yard long enough, will I get to Georgia?" he asked.

"No," I said. "Georgia is not 'under' the ground. It's below Tennessee on a map."

"So, if I dig, where will I come out," he said.

"Oh, I don't know, maybe China?" I said.

"I've noticed a lot more Chinese people around these days," he said.

"What do you mean?" I asked.

"I've just seen a lot more Chinese people walking around our city."

He paused for a minute to look at some cows out the window.

What an odd age, I thought. So much vocabulary and so little context.

These are the moments that I try to freeze in my memory, knowing that one day I may be the child again and he may be the adult groping to add context to our conversations. I feel a wave of melancholy, which often ripples through your emotions when you're an older dad with very young children.

But it soon passes, replaced with the knowledge that, in this instant - in the precious present - life is good.

"I love my Daddy, and I think he loves me," my son says sweetly, waiting for my reply.

"Your Daddy loves you a million miles," I said.

"And I love you infinity times infinity," he said.

Until I had a family, it didn't occur to me that love can actually fill up infinity. Now, I have no doubt.

Contact Mark Kennedy at mkennedy@timesfreepress.com or 423-757-6645. Follow him on Twitter @TFPCOLUMNIST. Subscribe to his Facebook updates at www.facebook.com/mkennedycolumnist.