Don't forget to put on your white lab coat Saturday night because you'll be witnessing fundamental science in action. If you have kids, be sure to sit them down to experience a critical lesson of nature as it unfolds before their eyes.

This petri dish, more appealing than what you would find in biology class, will be the premier venue of the Sweet Science. It's a simple platform surrounded by four burgundy ropes, the very ring used in Madison Square Garden since the days of Jack Dempsey.

A heavyweight group of substantially lesser distinction will climb into that legendary ring Saturday night, when five bouts — four of them televised on pay-per-view — will provide a wonderful case study in Darwinism.

Five winners certainly will continue their careers, while five losers will come one step closer to extinction. It's survival of the fittest, and in every bout the loser will face more significant consequences than the winner will receive honor.

There won't be any legacies fortified, at least not in a positive way.

But the defeats will go a long way in stimulating the heavyweight circle of life, which for the past 20 years has been turning over less frequently than the Cuban government.

For those not familiar with Don King's show, IBF champ Chris Byrd will fight Jameel McCline, WBA champ John Ruiz will face Andrew Golota, and former undisputed champs Evander Holyfield and Hasim Rahman will take on Larry Donald and Kali Meehan, respectively. On the untelevised portion of the card, DaVarryl Williamson will meet ex-champ Oliver McCall.

A tragedy is about the only thing that will make this night historic, but the card does possess a certain level of intrigue.

It should be cathartic. So many fighters on this card, maybe even all of them, have hung around too long. Come Sunday morning, much of the division's dead weight might be buried. Just as trees need to be pruned to facilitate new growth, some heavyweights are in need of getting clipped.

Boxing fans shouldn't be despondent if any of these fighters went away. The division will never move forward as long as we cling to the hope many of these retreads will provide any lasting measure of hope.

Who among us would become despondent if we never saw elderly Holyfield,  uninspiring Byrd, boring Ruiz, underachieving Donald or undistinguished Meehan fight again?

We could do without all of them, actually, but at least Rahman, Golota and McCline are remotely interesting and could remain as such for a few years to come.

The optimal scenario for the well-being of the division would be the following:

* Williamson stops McCall to help drive The Weeping Willow off the scene as quickly as possible.

* Donald treats Holyfield similarly (without viciousness), just to push The Real Deal one step closer to reality.

* Rahman continues his comeback by defeating Meehan in impressive fashion.

* Golota stays on his best behavior and handles Ruiz; otherwise it will be Ruiz-Rahman again, and nobody wants to see that.

* McCline beats Byrd to end another dull championship reign.

* WBC champ Vitali Klitschko crushes Mike Tyson conqueror Danny Williams on Dec. 11 to further establish himself as the Alpha heavyweight, a role that still must be solidified.

* Aliens colonize Earth to create a super-race of athletes that save boxing, at least until they learn how to drive and opt for NASCAR domination instead.

OK, so one of those ideas is pure fantasy: There's no way Holyfield will retire, even if Donald beats him. I should know better than that.

Holyfield, 42, refuses to entertain the notion of retirement. He insists he won't walk away from the sport until he has all three major title belts. He currently has zero, and his match with Donald won't get him one either.

How far gone is Holyfield? Monday will mark his 20-year anniversary of turning pro. He is 2-4-2 in his past eight fights, dating back to 1998. He hasn't fought since James Toney dropped him to his knees with a body punch in October 2003.

“You look at the past fights and you can say that my skills have declined for what you have seen, and I wouldn't be mad with them,” Holyfield said. “I would tell them 'You are absolutely right.' But what has that got to do with the 13th?”

Sounds like Evander should change his nickname to the Real Denial.

“You have to understand that a lot of people that [say I should retire] have never been a winner,” Holyfield said. “I have. They never did. They never completed anything. They never went through that. I came from the ghetto. I always had a rough time and I had to make adjustments. I went through my whole life making adjustments.

Donald clearly knows what he's up against. Perhaps he can be to Holyfield what Glen Johnson was to Roy Jones Jr. — confirmation that it's over.

“Evander is a warrior,” Donald said. “He is a champion. Champions don't die easy. They keep going. You have to take the fight away from a champion. … But in watching the films and whatnot, I don't see myself having any problems with Evander.”

Don't get too confident, Larry. You're no world-beater yourself.

Donald will be 38 years old in January and has a paltry 3-2-1 mark over the past four years. His losses were to Kirk Johnson (back when the Nova Scotian gave half a damn) and Klitschko, but his victories came against pugs James Stanton, Sedrick Fields and Mario Cawley.

Two of the more monotonous heavyweight title reigns in recent memory can come to an end Saturday night if Byrd and Ruiz lose.

Byrd has looked lackluster in his past two bouts and has been lucky to retain his belt. The slick 34-year-old southpaw met Golota in April and escaped with a controversial draw and then somehow won by a comfortable margin on two scorecards against Fres Oquendo in September 2003. His only other bout in the past 2 1/2 years was a unanimous decision over Holyfield.

McCline is 34 years old and won't have many more chances like this — if any. The 6-foot-6 colossus took an impressive streak of wins over Michael Grant, Lance Whitaker and Shannon Briggs and parlayed that into a miserably unsuccessful shot against then-WBO champ Wladimir Klitschko in December 2002.

McCline, who won only two of his first five pro bouts, has climbed back into contention with consecutive victories are over Charles Shufford, Cedric Boswell and Wayne Llewelyn.

“I love this match-up,” Byrd said. “Jameel is the biggest, most athletic guy I have ever fought. I think when the fans first see us in the ring, they will think he will beat me easily. But I know how to fight big guys and by the third or fourth round, it will be a different story.”

Byrd, like Jones, has shown signs that age has caught up to him. He isn't eluding the big punches like he used to, and while that might create a more a more entertaining fight, there's a strong possibility McCline could rock him.

On paper, the Ruiz-Golota match is the most significant because it could thrust the wildly talented and mentally unstable Golota back into the limelight. But the bout could just as easily turn out to be a fantastic dud.

Each fighter loves roughhouse tactics. Golota is infamous for meltdowns of all sorts, but his inexplicably repetitive low blows against Riddick Bowe were what saddled him with the The Foul Pole moniker.

“It's going to be a fight, the low blows and hitting behind the head,” Ruiz said. “You know it's going to be a great fight. I'm looking forward to it. His style against my style is going to be an explosion.

“This is a perfect fight for me. Like you've seen in a lot of other fights, he just ends up quitting. What better opponent to have than someone who is going to end up quitting on me as soon as I put the pressure on?

Ruiz, 32, will use any part of his body — elbow, shoulder, head — to manhandle an opponent. It's hard to say whether he's more frustrating to fight or to watch.

“He's a dirty fighter,” Golota's trainer, Sam Colonna, said. “You have to be careful. He hits behind the head, he hits low. When Andrew does that he gets disqualified. When John Ruiz does it, he finds a way not to get disqualified and win the fight. Against John Ruiz, we are going to be prepared for anything he does.”

Golota will turn 37 in January, and he's the sentimental choice of many fans because his story is one of redemption. Until his draw with Byrd, Golota frittered away every major opportunity he had, twice against Bowe in 1996, folding like origami against Lennox Lewis in 1997, quitting even though he led on the cards in the 10th round after getting knocked down by Grant in 1999, wetting himself against Tyson in 2000. Golota stayed out of the ring for nearly three years before resuming his career last year.

“For me, if I don't win this fight I retire,” Golota said. “I'm getting too old to train this hard for this many weeks for nothing.”

Rahman shares that same attitude. He has been scraping along since 2001, when Lewis exacted revenge with one of the filthiest knockouts a fan can hope for, authoritatively taking back the titles lost when Rahman shocked the world a few months earlier.

“If I don't win this fight, you won't have to hear me say it again, because I won't fight again,” Rahman said. “How about that? Did you hear me say that? I won't put on the gloves again if I don't win this fight.

“I liken my career to a baseball game. I've got two strikes. One more strike and it is over, then I'm out. That means I can't afford to get a third strike so I have to go out and win. Not only do I have to win, I have to win impressively.”

The loss to Lewis began for Rahman a 0-3-1 skid that didn't end until he regrouped with a brand new gameplan early this year. He feasted on a steady diet of cupcakes, doing so in such a way — four victories in a 4 1/2-month stretch — that his confidence has returned.

“They just got me back on a rhythm in terms of keeping my body in shape and taking my body to the next level,” said Rahman, who turned 32 this week. “That's exactly what I did to get to the title in the first place. I had to take those types of fights to work my way up the ladder and do what no other prospect would do. I feel like I am the best prospect in the game, and now I want to be champion. After this fight, I will go on to win the world title.”

Meehan is a bit of a wild card, but Rahman should handle him. The 34-year-old Aussie doesn't even box full-time and doesn't boast a meaningful victory on his 29-2 ledger. This will be only the sixth time he has fought outside of Australia or New Zealand.

He gained a modicum of legitimacy when he fought valiantly in a controversial split-decision loss to lightly regarded WBO champ Lamon Brewster in September. Williams knocked Meehan out in the first round when they met for the British Commonwealth title in 2001.

“This is a true match of two heavyweight fighters,” Meehan said. “Each fighter should be
able to knock the other fighter out because we are trying to knock people out. We are two strong men. I can't stand here and say there is no way in the world Rock can knock me out because I am only human and he is only human, too. But at the same time, I can say I can knock him out.”

As for McCall, should be in trouble against the surging Williamson. McCall is 13-0 with one no-contest since breaking down against Lewis almost eight years ago, but the biggest name on that list is ubiquitous novelty Henry Akinwande.

Despite his streak, McCall isn't exactly sharp. He's 39 years old and has spent much of his recent years behind bars. He summed up his frame of mind last month, when he appeared at a media event the afternoon of Felix Trinidad's comeback triumph over Ricardo Mayorga.

“I'm going to fight until I hit the mat,” McCall said, appearing a bit disoriented. “The day I get knocked out will be the day I retire.

“I'm looking forward to seeing who gonna knock Oliver McCall out! I wanna know who gonna knock me out!”

Me, too.

And I hope it's soon.