Given that one out of eight people are left-handed, the odds of a foursome having two left-handers is 1/8*1/8*7/8*7/8*6=7% (appoximately) So, while not common, it shouldn't be rare either. The assertions in this piece would be more credible if it could be shown that the 7% are proportionally more successful/interesting than the 93%. If not, then something else must account for the Beatle's magic.