They might be the icons of a musical revolution in the early 1960s, but now science is questioning whether The Beatles' music from that era was important.

"I think that our estimation of the Beatles' importance at that time, or how we think about them, has become vastly inflated," evolutionary biologist Professor Armand Leroi from Imperial College London said.

He said the music that launched the Beatles onto the global stage — including songs like I Want To Hold Your Hand, She Loves You and Ticket To Ride — "is in fact relentlessly average".

And he said he had scientific evidence to back those claims up.

What can science tell us about the Beatles?

In a study published in 2015, Professor Leroi and his colleagues tracked the evolution of US pop songs between 1960 and 2010.

They measured specific musical characteristics in the top songs on The Billboard Hot 100 chart of each year.

The researchers used audio processing software to extract changes in chord sequences, and put these into broad "harmonic" categories.

The rise and fall of harmonic (H) and timbral (T) characteristics in the Billboard Hot 100 chart between 1960 and 2010.

Similarly, they tracked how timbre changed in songs over the 50 years.

These "timbral characteristics" looked at which instruments were being played, and the overall character of the music.

Using these musical blueprints, Professor Leroi said his team was able to track exactly how pop songs were changing over the decades, in a similar way to how researchers track evolution using genetic material.

They then used this data to figure out when popular music was changing dramatically.

"We developed some statistical techniques to actually quantify revolutions — that's to say rapid accelerations in the rate of change of music," Professor Leroi said.

"We identified three, and they were centred around 1964, 1982 and 1991."

Professor Leroi said the data shows a 1964 revolution that was all about music becoming more "aggressive". But The Beatles did not contribute to that change in the music.

"They're not making that revolution, they're joining it," he said.

"This revolution — and you can see it in the numbers in the charts — actually begins long before 1963 ... even earlier, where our data don't go."

Professor Leroi said that change in musical style was largely driven by other bands, playing louder rock and roll.

"When the [Rolling] Stones, the Kinks and the Who were transforming the face of popular music, Lennon and McCartney were writing ditties for prepubescent girls," he said.

"That's not saying they didn't have nice tunes, it's not to say they didn't have nice haircuts, or that they weren't nice boys, but in terms of driving the music ahead, they just weren't that important."

That can't be the only way to figure out The Beatles' impact?

Forensic musicologist Joe Bennett from the Boston Conservatory at Berklee argues that, even in their early years, The Beatles were making ground-breaking music.

"The Beatles could sound like chanson, or orchestral music, or rock and roll, or folk balladry — and you could get all of that in some cases in the space of one single album," he said.

Professor Bennett points to songs like Yesterday, released in 1964, where the band experiments with form, and brings a string quartet into a traditional pop song.

"This is a boy band not two years out from their first hit," he said.

Professor Bennett said many of The Beatles' other early innovations, such as their use of studio production techniques and lyrics, wouldn't necessarily register in a big data analysis — a point that Professor Leroi agrees with.

"When I say that the Beatles weren't musically important, I mean that they weren't important in a very specific way at a very specific time," Professor Leroi said.

What were the other major revolutions in popular music?

"Everybody thinks they know when the music changed. And when the music changed ... was usually when they were about 17 years old," Professor Leroi said.

"The belief in the importance of the music of your youth and the arbitrariness of revolutions and change and so forth, and the journalistic nonsense that has been written about it, all conspire I think to make the history of pop deeply opaque and deeply subjective."

Armand Leroi has studied the musical complexity of The Beatles' early work and says it's not as revolutionary as we might think.

But Professor Leroi said his research gives an objective way of looking at musical revolutions.

Aside from the 1964 revolution, he said his data points to another major change in music in 1982, stemming from the introduction of drum machines and synthesisers.

"[These] just obliterated the musical landscape, such that everything sounds like early Madonna or Duran Duran," Professor Leroi said.

He said there was a third revolution in 1991 when hip hop and rap took over the charts.

"All sorts of songs which don't have chords in them, or have very few chords in them, and have lots of speech in them, start cropping up," he said.

Professor Leroi said while the Beatles did not contribute to the 1964 revolution, their later work may have been more musically important.

But he said objective scientific research may help re-evaluate claims about their earlier songs.

"We just forget then about the fact that the songs themselves weren't actually that remarkable," he said.