It is pretty to think that Barry Bonds wrote the final chapter in baseball's steroid era when he broke Hank Aaron's all-time home-run record Tuesday night.

Actually, it's pretty naïve.

Maybe the most troubling thing about the last few weeks has been the way dialogue about Bonds and beyond echoes what people were saying five, 10, even 20 years ago. There is the same head-in-the-sand posture from Major League Baseball, its players, and much of the media that cover the game, as there was when fans were chanting "Steroids, steroids" at Jose Canseco in 1988 or cheering Mark McGwire and Sammy Sosa a decade later.

We don't know exactly when baseball's steroid era began. The idea that Canseco and the late-1980s Oakland Bash Brothers invented it is simply misguided. It is generally overlooked or forgotten that Pete Rose's bet runners, Tommy Gioiosa and Paul Janszen, were up to their deltoids in steroids - and both had access to the Reds teams Rose managed. That would establish a possible link in the mid-1980s.

If the beginnings of the steroid era are fuzzy, the end will be impossible to see through the haze of dissemination, sleight-of-hand and inadequate testing. The one thing we can be reasonably sure about is that it is not here yet. It probably isn't even close.

The lesson from the last 10 years or so - in baseball and other sports - should be as clear as the Balco Clear: Wherever there is a good chance of getting away with it, there will be cheating in professional sports. And wherever there is a reasonable chance of getting caught, there will be cheating in professional sports.

The recently completed Tour de France is a shocking example. A year after the event's winner tested positive for synthetic testosterone, after many of the top riders were caught or banned or dropped out because of scandals and investigations, the 2007 Tour was again stained by cheating.

If cyclists will cheat under such stringent testing and unblinking, watchful eyes, why wouldn't a major-league pitcher or an NFL linebacker use substances no one is even testing for?

Ethics? A sense of fair play? Sportsmanship? If you can even suggest one of those with a straight face, you haven't been paying close attention.

One of the prevalent, and most disturbing, Bonds angles has been the possibility that a "clean" athlete - presumably Alex Rodriguez - will break the home-run record relatively soon, that there is consolation in the prospect that Bonds won't hold it as long as Babe Ruth or Hank Aaron did.

This angle is uncomfortably similar to the steroids-won't-help-baseball-players mind-set that kept many baseball media types from taking the subject seriously 10 years ago.

Who knows whether A-Rod is truly clean? Who knows if Ryan Howard or Albert Pujols or Prince Fielder or anyone is truly clean? It is an indictment of Major League Baseball, the commissioner's office and the players' union that we can't be certain about any player.

The steroid era won't end until we can.

It is true that baseball finally began seriously cracking down on anabolic steroids and other substances in 2005 - after congressional hearings embarrassed commissioner Bud Selig, a handful of star players, and the game itself. It is also true that a handful of players have been caught and suspended under the new testing policy.

They tend to be little-known, often minor-league players. That tells you either that baseball isn't trying all that hard to catch the big names or that the testing is working only on players who can't afford the really good, really expensive stuff. Or both.

Meanwhile, there is no testing for human growth hormone in baseball or any other major sports league. Apply the lessons of the last few years and you're forced to conclude that the hormone is being used by a significant number of players, and that effective testing will serve only to drive the cheaters on to the next thing.

One of the prime reasons for suspecting Bonds - the dramatic change in his appearance, including the size of his head, late in his career - simply doesn't apply to many of the game's young stars. We have no "Before" pictures of Rodriguez or Pujols. That doesn't prove they're clean, only that they came along after the culture of cheating was well-established and more sophisticated.

It would be a mistake to believe the cloud over baseball disappeared with No. 756. Worse, it's a mistake we've made before.