Six months after my oldest son was born, right around the time he first consumed a meal that wasn’t of the liquid variety, I experienced The Smell.

The stink belied his angelic, cherubic face, and I couldn’t believe my 17-pound bundle of sweetness could emit such a pungent, acrid and slightly putrid odor. Solid food transformed the mild scent of breastfed baby poo into the straightforward funk we all associate with poop, and Blake’s fruit-filled infant breakfast of champions was now leaving behind turds that rivaled those of any full-grown adult.

Solid-food poop made it much easier to detect when he needed a diaper change, but most times, the scent was more subtle.

“Do you smell something?” my husband asked me once.

“I think so,” I said. “Let me check.”

Without thinking, I hoisted my son upward, pressed my nose to his diapered bottom and took a sniff. P. U. The kid was rank. Time for a diaper change.

At the time, I had no idea that my action connected me to generations of mothers who, for millions of years, had done the exact same thing to confirm their little ones had soiled themselves. Well, maybe not millions of years — cave mothers likely had no doubt that little Oog and Moog were stinky since little more than a loincloth likely covered their bums. The practice of baby butt sniffing likely began in this more recent era of well-constructed diapers, which make it a bit more difficult to know exactly when a child has done a No. 2.

I started paying more attention to this particular interaction among other parents, and saw multiple moms at the playground scoop up their little ones and sniff their butts. A mildly bewildered expression appeared on the babies’ faces, and I enjoyed guessing what they were thinking.

“Mom, what the heck? Not in front of my friends!”

Really mom, is all that necessary?” 

“I bet you wouldn’t like it if I sniffed your butt in public!”

It’s not just moms sniffing their own children’s behinds. When we traveled north to visit grandma and grandpa, my son scampered around their living room without a care, eager to investigate a new world of shiny, breakable objects in a non-baby-proofed space.

He stopped for just a minute, grunted, and started running again. I didn’t notice, but my mother did. She promptly picked him up, sniffed his butt, wrinkled her nose and grinned. She declared that he indeed needed to be changed.

She was another baby butt sniffer! Had she done that with me? With my brother?

“Of course,” my mom said. “It just comes naturally.”

A mother doesn’t have to be related to a child to do the butt sniff. One new mom brought her young one to a meeting, and another mom whose children were now in their late 20s volunteered to hold the infant. Since her progeny had yet to bring any grandchildren into the fold, she said she was happy for any opportunity to hold a baby again.

The little girl, 13 pounds of sugar, spice and adorable brown chipmunk cheeks, emitted a tiny groan. The veteran mom gently pressed her nose to the baby’s bottom.

“Looks like she’s given me a present,” the woman said sweetly.

I was amazed at how she seemed so at ease smelling an unrelated child’s bum. And, none of the other women blinked an eye.

It must be a mom thing, because my husband refuses to follow my example. He’ll tell me he smells something foul in the air, likely from our son, but won’t ever do a definitive butt whiff.

“That’s just weird,” he’s said, grimacing at the thought.

Instead, he’ll take off the baby’s clothes and prepare to change the diaper only to discover that what he thought was poop was merely a fart. Five whole minutes – a valuable chunk of time in those early parenting days – down the drain because of his downright refusal to just pick the baby up and sniff already.

My husband still won’t perform the sniff test, but he has conceded to my special powers in this arena. If we smell an odor in the air, he asks me to confirm. If I recoil abruptly after a little lift and sniff, we know it’s time for a diaper change. If I linger, taking a few extra sniffs to make sure my diagnosis is accurate, our son is probably fine.

The smell was probably just a fart. Maybe the baby wasn’t even the source of the fart. Maybe we all just smelled some rotten food lingering in the air and needed to take out the garbage that’s been sitting in our kitchen a bit too long.

Now 3 years old, Blake runs to the potty – most times – when he needs to go, sparing me from the need to sniff. I didn’t lose my touch though — his brother arrived in late 2015, and my out-of-this world olfactory senses are being put to the test again.

He and other malodorous babies in my vicinity better watch out – they might find me lifting them up and inhaling their smelly little cheeks.