If this odd little decade has a credo, it is probably "Lighten up." That is precisely the kind of advice provocatively ignored by "Thirtysomething," the earnest and earthy new ABC drama series about two baby-boomers and their baby, premiering at 10 tonight on Channel 7.

The series, from the talented team of Edward Zwick (writer-producer) and Marshall Herskovitz (writer-director), attempts to deal on a straightforward and intimate level with the joys and woes of first-time parenthood and modern marriage. It struggles to prove there is such a thing as yuppie angst.

There is also such a thing as network nervousness, and, reportedly, the superserious tone of the first show will be softened (lightened up?) in future installments, on orders from ABC executives who fear the show will be perceived as a downer by the very audience, young adults, it aims to please.

As Hope and Michael, the fitfully happy couple who say "thirty-something" when asked their ages, Mel Harris and Ken Olin have attractive rough edges and a palpable connubial chemistry. The NBC series "A Year in the Life" aspires to the same level of domestic realism, but it seems slicker and glossier than "Thirtysomething," and therefore less believable.

However, both Hope and Michael are afflicted with a condition that could turn them into major irritants: They are able to articulate, sometimes at length, every emotion and anxiety they feel. And they feel plenty. Not a thought goes unspoken in this house, and as a result, a certain nagging whininess sets in.

You may occasionally wish they would both find themselves at a loss for words.

When in doubt, though, director Herskovitz can always cut to the baby, one of the cutest babies ever in a TV series. Cute as she is, one also appreciates -- especially if one has been in similar straits -- the trials and disruptions home life can bring.

The couple worry that the baby will never get into a day-care program, much less a decent college. The husband balks at spending $278 for a stroller. The wife wonders (aloud, of course) when their sex life will resume. Both feel like zombies after a night in which they got two hours and 45 minutes' sleep.

And in probably the most credible sequence, the wife interviews a series of baby sitters and rejects them all as unqualified -- including one who is obviously completely qualified but also has the gorgeous glow of a particularly healthy pompon girl.

Hubby is having enough trouble controlling his roving eye at work, where a preponderance of pulchritude subverts the innocence of a lunchtime stroll. Fidelity begins to seem as lofty a goal as world peace, and no more attainable. Meanwhile, in his young advertising business, the husband tries to hold true to long-held values in an environment that encourages compromise.

This conflict is radically uninteresting.

Back at home, just when all seems a shambles, the baby smiles. "Do all kids radiate light," asks Hope, "or is it just her?" Frequently enough to be satisfying, "Thirtysomething" plunks the proverbial responsive chord.

The child affects virtually all aspects of the young couple's lives, including Hope's friendship with Ellyn (Polly Draper), who knew her long before her wedding and who has a hard time adjusting. The tension and jealousy are nicely developed, though some viewers may wonder if Ellyn's interest in her friend is purely platonic.

What the couple needs is some quiet time. So does the viewer. Perhaps it was thought that as much detail as possible should be packed into the pilot, but it's almost exhausting. However it unfolds over the coming weeks, "Thirtysomething" is off to a promising, if excessively talkative, start.

'Jake and The Fat Man'

As a television crime-fighter, District Attorney J.L. McCabe is head and shoulders above the competition. But his head and shoulders are not the first things you notice about him. J.L. is "the Fat Man" in "Jake and the Fat Man," the new CBS drama series premiering with a two-hour episode at 8 tonight on Channel 9.

Pay no attention to the one-hour "Jake and the Fat Man" episode that the network awkwardly scheduled and aired Saturday night. CBS is in its decline and its programmers are dotty. The pilot that airs tonight is really the premiere, and it's an audacious departure from crime show formula.

That's mainly because of the irascible incorrigibility of the hero. Television has been home to many a "gruff but lovable" cuss, but McCabe in his disheveled cantankerousness has real dimension -- at least as played by the burly and corpulent William Conrad, tearing into the role like Henry VIII demolishing a pheasant.

An impudent note is sounded with Conrad's early appearance as McCabe in court -- asleep. He wakes up in time to win a conviction with a hokey burst of hambone theatrics. Love at first snore! And it only gets better; McCabe lives in a wonderfully homey dump, has a slovenly bulldog who's even jowlier than he is, and often repairs to a bar where the beautiful Anne Francis croons balmy ballads warmingly.

As for crime-solving, most of the legwork is handled by Joe Penny, as Jake, a slickster in sharkskin who's not nearly as amusing as Conrad's McCabe. The murder case on the premiere is better than usual in this kind of show, though, and the program opens with an audacious bedroom scene involving clandestine lovers and a gun kept on a closet shelf.

Douglas Stefen Borghi wrote the crackerjack script, which Ron Satlof adroitly directed. The executive producers are Dean Hargrove and Fred Silverman -- the same team whose "Matlock" series, on NBC, is as mediocre as "Fat Man" is fresh.

One of the producers' gambits was nixed by CBS censors. In the original premiere, McCabe spouted a string of (presumably) four-letter words that were masked on the sound track with bleep sounds. CBS got scared and bleeped the bleeps, replacing them with alternate footage using milder strong language.

A CBS spokesman said yesterday the bleep noises had to go because censors felt "many people watching would still be able to discern what he was saying" by reading Conrad's lips, and that what he was saying was "unacceptable language." McCabe will be limited to hells and damns. This shouldn't really be much of an impediment, but like most network censors, the chaps at CBS are probably just being silly.