Very intelligent question! The appendix in humans is known as a vestigial structure. Vestigial basically means ‘left over from a past time’. Other mammals have an appendix which is still used to digest cellulose, a plant material which is actually quite a troublesome material to digest. Charles Darwin proposed that our own appendix was once used to digest the same tough tissue but as we progressed to eating a diet of foods more easy to mulch up in our intestines, we eventually lost the need for our appendix. However, that doesn’t alter our genes! Our genes don’t really respond to external factors like that- so during embryogenesis (the development of babies at the very early stage) we still grow our appendix because our genes instruct us to. It’s thought that the appendix has taken on a secondary function (in humans at least) to harbour friendly gut bacteria and flora to aid digestion and keep us nice and healthy down there.
Apparently- the larger your appendix the better- since smaller ones are more vulnerable to betting infections!
There are lots of examples of vestigial structures in animals- not just humans. See if you can find any more examples! It’s a lovely strand of evidence that demonstrates that we all share a common evolutionary history! Hurrah!
I actually had to have my appendix removed so I feel I’m a bit too well acquainted with that organ:) We don’t really know but people think the appendix use to house bacteria which helped us digest tough plant food back when people didn’t learn yet how to use fire. It’s really just one of the idea though – and great question thanks!