Despite what you may have heard, your appendix might not just be hanging around uselessly taking up space.
(Unless you've had it removed, that is).
Researchers from Midwestern University, Illinois, looked at the history of the supposedly-unneeded organ, which has appeared, disappeared and then re-emerged in mammals over millions of years of evolution.
They found that the organ has evolved at least 29 times, possibly more, and has been lost 12 times.
They concluded that the fact it has appeared more times than disappeared means it must have some sort of use, even if we don't know what it is yet.
The study states:
If it were selectively neutral, losses should be about as common as gain
The researchers say they can therefore “confidently reject” the theory that the appendix is merely an evolutionary hangover, and something that we’ve evolved past the point of needing.
One theory is that the appendix stores good bacteria to help us fight off infections.
The researchers’ findings suggest that it plays a part in our immunity, calling it a "microbial safe-house for beneficial bacteria".