My wife and I had been quibbling all day, due to the stifling heat and humidity of the sea level jungle in which we had been camping. We took the road toward Mexico City, hoping that higher elevation would gain us some relief from the tropical heat.

On a switchback road several thousand feet above sea level, my dear wife announced the need to use the convenience, and lurched toward the rear of the van. I suggested that she wait until I could pull over, but she was resolute in her determination to attend to matters promptly.

From the back, I heard her irritable voice say, "Why's this sodding potty rocking?" I pondered, and realized that the potty was under pressure! It had been last used at sea level, and we had gained significant elevation. The bottom of the potty was bowed with pressure, causing the rocking. And, to my good wife's impending grief and mortification, the potty was nearly full.

A beat too late, I called back, "Honey don't flush..."

I was interrupted by a mighty "WHOOSH" and a slurpy noise.

Then silence. Then a horrible stench, and the unhappy sounds of my dear bride cursing like a Liverpool longshoreman. In the rear view mirror, I saw that the interior of the van was dripping with brown fluid. Since she had to face the potty to flush it, and since she hadn't put the lid down, my hapless wife had taken the full blast from the pressurized holding tank. She looked like Al Jolson in blackface.

Convulsed with laughter which was the proximate cause of our subsequent marital decline, I pulled over. My soon-to-be-ex lady marched down the highway cursing and dripping. When I recovered my composure, I cleaned the van and picked up my luckless hitch-hiking wife. Our conversation was limited over the next few days, and never regained it's former gaiety and charm.

That pressurized potty took us out of the gene pool.