Alabama defensive lineman Jonathan Allen, the The Post’s 2012 All-Met Defensive Player of the Year, returns a fumble 30 yards for a touchdown late in the third quarter. (John David Mercer/USA Today Sports)

They’re 290 of the damnedest pounds anybody ever saw, and as they began to move the way 290 pounds seldom do, most of the 101,821 at Bryant-Denny Stadium wreaked another wall of Saturday sound. They, after all, were witnessing the fearsome optical near-illusion of Jonathan Allen, the turning of a big game and a telltale microcosm of another soaring Alabama autumn.

All the 290 pounds belong to Allen, with not a one of them seeming spare on the Alabama senior defensive force who was The Post’s 2012 All-Met Defensive Player of the Year. He has gone from a coveted prep sensation at Stone Bridge High in Ashburn to a pillar of a man who adores his Tuscaloosa, and on Saturday, he went from the Texas A&M 30-yard line to the end zone.

There, the ground sort of shook, but some realities solidified.

For a remarkable 12th time in eight games, No. 1 Alabama had a “NOT,” a non-offensive touchdown. For the second time, Allen had a touchdown. And for the eighth time in eight games, Alabama would have a bruising win, this time in a tangle with No. 6 Texas A&M, in a game that stood at 14-13 to the visitors early in the third quarter, 20-14 to Alabama when Allen scooped up the ball, 26-14 when he finished and 33-14 by the end.

As the third-quarter clock ticked to 23 seconds left, 22, 21, and Allen made his charge up the left sideline, a curious game deflated then and there. The rest felt like filler.

“That was the real turning point in the game. That changed the momentum of this game,” said Alabama Coach Nick Saban, already the winner of four of the past seven national titles.

“You know, you don’t think about it,” said Allen, himself a national champion once already. “It’s all reaction. So we just train ourselves to pick up all loose balls in practice, and it’s good to see happen in the game.”

“He moves pretty good for 290 pounds,” said defensive back Minkah Fitzpatrick. “You really don’t see some people move like he does. He’s really explosive off the ball. He’s physical, too. It’s kind of hard for the offensive line to block him. He makes plays and gets to the quarterback really fast.”

Allen had done that on a sort of “Superman” move for an early sack of Texas A&M quarterback Trevor Knight, who had so tormented the Crimson Tide while playing for Oklahoma in the 2014 Sugar Bowl. That, too, he pooh-poohed, saying, “Just reaction. You don’t have time to think out there.” As Alabama looked frightening in just about every way, even two blasting kickoff-return hits from freshman linebacker Mack Wilson, it cruised out to a 13-0 lead.

When the Aggies (6-1) made things curious, scoring just before halftime and just after halftime, the noise came only from their Corps of Cadets, their sliver of fans in maroon up one corner of the stadium and their stripe of more fans at the very top. Alabama had carried the look of dominance, outgaining Texas A&M 129-25 after one quarter and 303-150 after two, yet it trailed.

Anyone fretting at that moment must have forgotten a central tenet that extends well beyond Tuscaloosa this college football season: Alabama does have that defense.

Saban said the Crimson Tide switched from a “dime” defensive package to a “nickel,” which places a linebacker in the box rather than a safety, and counterbalanced the reality that, Saban said, “Their runners are heavy.” From there, after their third-quarter score on two Knight throws covering 58 yards, the second going 25 yards to Christian Kirk in the back right corner of the end zone, they had five possessions. They ran 30 plays. They gained 52 yards.

Their offensive line began to look more and more inconvenienced.

Then it began to look deluged.

The caliber of 21st century athlete opposing them finds some exemplars before you even get past the letter “A,” in the linebacker Ryan Anderson and in Allen. After freshman quarterback Jalen Hurts benefitted from an ill-considered, third-down roughing-the-passer penalty against Texas A&M’s Shaan Washington and led a 14-play, 77-yard drive for the lead on a four-yard pass to Calvin Ridley, Anderson and Allen collaborated.

On third down and 26 after Alabama held a team meeting around Knight for a sack, Knight handed to Keith Ford, the back who had a decent day with 62 rushing yards. As Anderson approached from the left almost to take the handoff himself, the exchange got all muddled and the ball got all spilled. With no time to think, Allen scooped it up as would a 190-pound person and made off for the end zone.

His fumble return meant Alabama has five fumble-return touchdowns, four interception-return touchdowns and three punt-return touchdowns in this season alone. Two have gone to Allen, and three to Eddie Jackson, the star senior safety who fractured his leg Saturday and is lost for the season.

Even with that bummer, Allen and teammates prepared for an off week set to be loaded with praise. “Not really worried about that,” he said. “We gave up a hundred yards rushing (specifically, 114). If we’re the best defense, we can’t allow that to happen. So there’s a lot of room for us to improve. We gave up a lot of plays.”

Well, technically, not a lot.