Mick Fleetwood and David Fricke discuss Fleetwood Mac’s early years at a South by Southwest panel on Wednesday, March 15, 2017. Peter Blackstock/American-Statesman

Given that the vast majority of the tens of millions of Fleetwood Mac albums that have been sold came after the mid-1970s addition of Stevie Nicks and Lindsey Buckingham to the Rock and Roll Hall of Fame rock group, it’s a fair bet that the folks who lined up for namesake drummer Mick Fleetwood’s South by Southwest panel on Wednesday afternoon may have been there to hear all about the making of “Rumours” and other band dramas from that era.

What they got instead was a fascinating, and more rewarding, deep dive into the band’s 1960s primal years. That’s largely thanks to the encyclopedic knowledge of journalist David Fricke, who interviewed Fleetwood for this conversation-styled session. That era is clearly what Fleetwood came to speak about, given that his new book, “Love That Burns: A Chronicle of Fleetwood Mac, Vol. 1, 1967-1974,” covers those years before the British blues band metamorphosed into a pop-landscape-changing butterfly.

Fleetwood and Fricke went into great detail about the genius of original guitarist Peter Green, who was responsible for bringing Fleetwood aboard in the first place (before the band was rechristened for Fleetwood and bassist John McVie, actually after an early song that was named “Fleetwood Mac”). The significant contributions of co-founder Jeremy Spencer, and later transitional members Danny Kirwan and the late Bob Welch, also got their due as the discussion twisted and turned through early albums such as “Mr. Wonderful,” “Then Play On,”  “Kiln House” and “Bare Trees.”

Fleetwood took pains to remind that Green was, at the time, a guitar star in Britain on the level with Eric Clapton, Jimmy Page and Jeff Beck (noting you were as likely to see “Green is God” declarations as the more historically cited “Clapton is God.”) And they eventually touched on the Buckingham/Nicks era as well, but in a way that made sense, explaining how the group’s early-’70s records already had started gradually steering the band toward the harmony-centered pop sounds that became their hitmaking hallmark (with Christine McVie having joined a few years before Buckingham and Nicks appeared).

The session included several wonderful intersections of history and humor, too, as in this exchange, after Fricke asked if Fleetwood was at a Feb. 11, 1970, show in San Francisco where Green sat in with both the Grateful Dead and the Allman Brothers.

“Yes, on acid,” Fleetwood deadpanned, before asking the crowd, “Has anyone got that (recording)?”

“Oh, it’s out there,” Fricke assured.

“Well we WERE out there,” Fleetwood confirmed.

The funny stuff kept the hour-plus panel moving right along, but it was Fleetwood’s much more poignant remembrance that brought the session to a close. Mentioning a two-hour phone call he had with Green while working on the book — and yes, he assured fans, there will be a Volume 2 covering the “Rumours” glory years and beyond — he said he’d wondered why Green had taken a chance on a young drummer with little experience so long ago.

“Why did you ask me to play drums?” Fleetwood asked Green.

“Mick, you were so sad, and you were really desperately unhappy and brokenhearted,” Green answered, referring to a recent breakup Fleetwood had endured. “This is what you need to do.”

We all are still reaping the benefits of that.