An evolutionary biologist got people swapping ideas about our lingering vestigia. Basically, this is the stuff that served some evolutionary purpose at some point, but now is kind of, well, extra. Here are the six traits that inaugurated the fun. Evolutionary anthropologist and Boston College a data-vivaldi-spatnav-clickable "1" href "http://dorsaamir.com" target "_blank" post-doc /a , a data-vivaldi-spatnav-clickable "1" href "https://twitter.com/dorsaamir" target "_blank" Dorsa Amir /a , started the whole thing with a a data-vivaldi-spatnav-clickable "1" href "https://twitter.com/DorsaAmir/status/1085227486869377024" target "_blank" series of eight tweets /a , and boy did she start something fun. Amir laid out a list of weird, once-useful details of the human anatomy that we continue to carry around within â and on â us. Basically, this is the stuff that served some evolutionary purpose at some point, but now is kind of, well, extra. p br /p p Natural selection, after all, has no reason to clear away unnecessary traits if they pose no evolutionary disadvantage. And when we say "started the whole thing," what we mean is that, this being Twitter, some arguing was inevitable. Some people took issue with Amir's use of the word "vestigial." One issue with the word is that early traits may still be beneficial in ways we don't yet know â the microbiome-managing a data-vivaldi-spatnav-clickable "1" href "https://www.webmd.com/digestive-disorders/news/20071012/appendix-may-have-purpose#1" target "_blank" appendix /a and the immune system's a data-vivaldi-spatnav-clickable "1" href "https://www.livescience.com/62447-tonsils.html" target "_blank" tonsils /a were both considered among these for some time. A trait's stated assumed value is also always just our best guess, so a certain amount of uncertainty is understood to be baked-in. It's important to remember, too, that if a mutation just happened to happen and persisted because it was useful, it's not the same thing as saying it has a em reason /em to exist. The em reason /em was randomness, unless one doesn't believe in evolution. br /p Which gets us to the second type of argument Amir's posts generated. Some creationist-intelligent design believers seem to be patrolling Twitter to shout down references to science where it arises. Probably this post will also get them going. Amir has nonetheless started a list and a conversation that is totally worth checking out, hair-splitting aside. Here are the six traits that inaugurated the fun.