It's called "repurposing of traits".
You might need the 3 things for function X, but the individual things might have a function in something else by themselves. Or be neutral and piggy back on other traits.
Irreducible complexity has been refuted so hard so many times already, it's like beating a dead horse. I'm amazed people still bring it up.
Where exactly has it been refuted? Do you even know what IC is? Do you even know that evolutionary biology is a historical science and that it is based on philosophy and not the scientific method?
Let me explain where most people get this wrong: they don't understand that it is a probabilistic argument.
But then, I guess, most people don't understand probability.
Michael Behe in Darwins Black Box(1996), pg 40:
Even if a system is irreducibly complex (and thus cannot have been produced directly), however, one can not definitively rule out the possibility of an indirect, circuitous route. As the complexity of an interacting system increases, though, the likelihood of such an indirect route drops precipitously. And as the number of unexplained, irreducibly complex biological systems increases, our confidence that Darwin’s criterion of failure has been met skyrockets toward the maximum that science allows.
An all too long series of 'accidents' for anyone who understands probability.
Yeah, so good-bye chance.
That is just one of the reasons why 'the third way' has been established which reflects researchers and authors who have, in one way or another, expressed their concerns regarding natural selection’s scope and who believe that other mechanisms are essential for a comprehensive understanding of evolutionary processes.
Among them James Shapiro, Denis Noble and Evelyn Keller.
The sad mechanistic view of evolution is dying thankfully.
Intelligent Design is also a far more robust Inference to the Best Explanation, and it is based on the scientific method.
Check it out.