Baseball's cave dwellers, the Houston Astros made the mighty Cincinnati Reds look Neanderthal again tonight, 4-1, with their marvelously infuriating brand of Stone Age ball.

The Astros moved within a half game of the first-place Reds as knuckleballer Joe Niekro won his 20th game and sidearm reliever Joe Sambito collected his 20th save before a standing-room-only Astrodome madhouse of 46,037.

These Houstonians, the folks who invented indoor baseball, have turned the game back to the prehistoric days of the dead ball in this cavernous park where home run hitters cry.

In the first game of this series, the Reds suffered 18 strikeouts at the hands of J. R. Richard (15) and Sambito (3). Cincinnati was even more frustrated this evening getting only four hits off Niekro's flutter balls.

When the Reds finally rallied, loading the bases with none out in the ninth, the exuberant cheerleading Sambito mowed down three straight Reds pinchhitters -- punching his fist as he fanned the first two, then going into a wild hatless dance as the last one flew out.

"I've never felt anything like this in my life," Sambito said. "I'm so high I'm floating. We're going to sweep them tomorrow and take over first place. We can't settle for less.

"It's too late in the day to kid ourselves. Their last six games are at home and our last six are on the road. To be realistic, we absolutely have to win again tomorrow."

"Realistic" is certainly the last work to apply to the Astros.

Baseball has had hitless wonders before, but probably no team has ever been so utterly punchless compared to the norm of its era. The Astros lineup tonight had five starters whose home run total for '79 was zero.

"That wasn't a nickel -and-dime offense tonight," beamed Niekro, the lesser-known younger brother of Atlanta's 19-game winner Phil. "It looked like a thousand dollar bill to me."

Typically, the Astros scored their first run off loser Pete LaCoss (14-8) on a ground ball, and got their last insurance run when a man scored from third on a strikeout which was also a wild pitch.

In between, Houston built a two-run inning around a feeble, chalk-kicking grounder down the first base line that the Red's Harry Spilman inexcusably never touched.

What can be expected of a team that has hit 46 homers this season - one less than Chicago's Dave Kingman? The Astros have hit only 13 balls over the Dome's fences this year. Their last homer with a man on base came July 6.

"We don't have any guys with superstar name tacked on our backs, but we've earned the respect of the other teams, including the Red's." When we got 10 games ahead of them, we got their attention."

The Niekro-Sambito show was a perfect Astro performance. Niekro's whole career was one long slump until after he turnes 30 and discovered the pleasures of the cavernous Astro-dome.

"Quite a few clubs let me go," he said. "I could have quit on myself and dropped the game, but my family supported me, kept encouraging me. Winning 20 almost 10 years after you've been told you're washed up is very satisfying."

Sambito, with a 1.76 ERA, has saved Niekro so often this year that he gloated, "Joe owes me about half his life. It was fitting that he got 20 wins and I got 20 saves on the same night. Sometimes I think all 20 have been for him.

"What I was throwing tonight was not the smoke I had the night before, but it was still a little warm."

In two nights, the Astros have not hit one ball that reached the warning track, as befits the first team in 30 years to have more triples than homers.Instead, they have turned the ground-ball single, the sacrifice bunt, and the steal into a pesky art form. Get a man to second - somehow, anyhow - then pray for miracles; that's the Astro theory.

The Red's seem the perfect proud foils for this tactic. All season they have looked at Houston as an annoyance that would disappear of its own accord. And Houston fans know it.

"Hey, Red's, kiss my Astros," read one Dome sign tonight, while another added, "Even Nixon hated the Reds."