Dorsa Amir is an evolutionary anthropologist and postdoctoral research fellow at Boston College. She's also pretty good at Twitter.
Amir often shares with her more than 11,000 followers interesting tidbits about her work and studies.
This week, she decided to tweet about "evolutionary leftovers" or, as scientists call them, vestigial structures.
She explained the first one in an appearance on AM to DM on Thursday. It's called the "palmaris longus."
As she wrote on Twitter:
Put your hand flat on a surface and touch your pinky to your thumb. Do you see a raised band in your wrist?
That there’s a vestigial muscle called the palmaris longus.
It used to help you move around the trees. About 14% of us don't even have this muscle anymore.