The just-updated résumé of Edward J. Markey points to one of the more unusual characteristics of the Capitol this year: It’s swarming with newbies.

When he moved his office from one side of the Hill campus to the other last week, the Massachusetts Democrat increased to 16 the number of members who have been senators for less than a year. That number hasn’t been larger in more than three decades, since the Reagan landslide ushered in the Republican takeover and a class of 18 freshmen in 1981.

In the past four years, moreover, the median years of service in the chamber has plummeted from 11 to six, because so many newcomers have replaced Senate icons.

So much for the case for statutory term limits — and so much more fodder to throw into the debate on whether experience is a force for good or ill in Congress.

When the 111th Congress convened four years ago, Markey’s predecessor, John Kerry, was among 29 senators who had already served for 19 years or more. Today, there are 17 on that roster.

At the same time, Markey’s transition continued the steady march of the old guard out of the House. He represented the Boston suburbs for 36 years and eight months before winning the special election arranged when Kerry became secretary of State. That’s the same as the collective service of the six members from Louisiana and more than the cumulative seniority in the House delegations of 18 states. With Markey gone, the House has only eight members who arrived before the 1970s.

Whichever Democrat wins the House special election to replace Markey in December, and whichever Republican holds the seat Rep. Jo Bonner is giving up next month to become the University of Alabama system’s top lobbyist will grow the size of this year’s freshman class to 74.

Beyond that, their arrival will push to 46 percent the share of House members who have completed fewer than three terms, a generally accepted benchmark for being labeled a “junior member.”

That percentage has been higher only three times since Dwight D. Eisenhower became president. The record was 56 percent in 1997, because of the two big GOP classes that made and then retained Newt Gingrich as speaker. But the number of junior members dropped significantly after the next election and has been below 40 percent ever since.

These numbers come from the latest update of Vital Statistics on Congress, which since the 1980s has been one of the most dog-eared and highlighter-stained reference works for everyone who covers the Capitol. (To keep the charts and tables as fresh as possible, Norman Ornstein of the American Enterprise Institute and Thomas Mann of the Brookings Institution have given up on print editions but are promising more regular updates online.)

The most obvious point here is that the movement to impose artificial limits on congressional longevity has no viable reason to exist anymore; the evolving natural political order is doing a fine job of culling the herd and assuring survival of the electorally fittest.

Although the Supreme Court ruled in 1995 that states may not put expiration dates on their House members or senators, the congressional term limits movement remained a genuinely important force as late as the turn of this century.

Since then, a series of wave elections, combined with the lengthening list of reasons for wanting to leave voluntarily, have kept the congressional churn at a brisk enough clip that the public has stopped complaining about a Congress in the thrall of “career politicians.”

As evidence of this, none of the constitutional term limits amendments proposed this year has more than nine sponsors.

A second takeaway is that the institutional memory in Congress has been fading fast. Whether that’s a good or bad thing will be debated around Beltway water coolers until the end of democracy.

Many will argue that the place needs a critical mass of veterans capable of explaining how the Capitol used to function at a much higher level — and maybe even persuading the confrontational generation of junior colleagues that backing away from the partisan bomb tossing and the rhetoric of rebellion might be a better long-term strategy.

Just as many will shout good riddance to the old-timers, arguing that their seniority-sourced powers and their fondness for the old ways of doing business are a main cause not only of Capitol gridlock but also of the nation’s fiscal, social and even international failings.

No sense that the argument’s been settled came out of last week’s deal to break the filibuster fever. Of the Republicans who sided with the Democrats on the key vote averting the “nuclear option” on presidential nominees, eight were first-termers and nine were more senior. That leaves open the question, at least on the GOP side, of which cohort is pushing which toward embracing a slightly less confrontational Senate.

Either way, the exodus of the elders is sure to continue. Not so much in the House, where early indications are that only a handful of the 28 lawmakers who have been in office at least a quarter-century are going to say farewell next year.

But another big drain of experience from the Senate is already guaranteed: The seven who have announced their retirements so far will have served a combined 28 terms. And four Democrats in the group — Carl Levin of Michigan, Max Baucus of Montana, Jay Rockefeller of West Virginia and Tom Harkin of Iowa — will have each been around 30 years or longer.

On top of that, another 84 years of service is claimed by three Republicans who might end up leaving next year: Thad Cochran of Mississippi, who’s still on the bubble about retirement; Mitch McConnell of Kentucky, who’s vulnerable in the general election; and Michael B. Enzi of Wyoming, who’s become newly vulnerable in the primary, which Liz Cheney, daughter of the former vice president, has announced her intention to run against him.

“It is necessary for a new generation of leaders to step up to the plate,” Cheney said in her announcement last week. “We can no longer afford simply to go along to get along.”

Whether the state’s voters embrace that rationale for her candidacy will shape the demographics of Congress for the rest of the decade.