Well actually, often just one mike.
I made my first recording (as part of a folk trio) in 1967, and we all stood round one very expensive Neumann mike. The balance was done by positioning, and if one of us made a mistake, we stopped and started again. This was in R.G.Jones studio in Wimbledon - one of the premier studios at the time. The engineers knew what they were doing. An album done in 2 3 hour sessions. Studios were booked in multiples of 3 hours back then, as this was the standard Musicians Union session.
Most of the pop records were recorded in a similarly simple fashion, first on to 2 track tape, with lots of bouncing down. If the band couldn't cut it in the first few takes, they just got in pro session players who could!! Hence a lot of pop records didn't actually have all the band playing on them.
By 1967, several people were experimenting with real multitrack, with the first 4 and 8 track machines becoming available. The Beatles being one notable example. However, I'm pretty sure that their first records were recorded straight to 2 track tape. And they still sound brilliant today, with a freshness that jumps out at you. A lot of this was down to the simplicity of the arrangements. Just listen - there is no superfluous stuff going on. The engineers and producers were largely responsible for licking people into shape, and paring down the arrangements.