Why Do We Smile?

Many species show off their teeth as a threat, so where did humans get our friendly smiles? Hosted by: Hank Green SciShow has a spinoff podcast! It's called SciShow Tangents. Check it out at http://www.scishowtangents.org ---------- Support SciShow by becoming a patron on Patreon: https://www.patreon.com/scishow ---------- Huge thanks go to the following Patreon supporters for helping us keep SciShow free for everyone forever: Kevin Carpentier, Eric Jensen, Matt Curls, Sam Buck, Christopher R Boucher, Avi Yashchin, Adam Brainard, Greg, Alex Hackman, Sam Lutfi, D.A. Noe, Piya Shedden, KatieMarie Magnone, Scott Satovsky Jr, Charles Southerland, Patrick D. Ashmore, charles george, Kevin Bealer, Chris Peters ---------- Looking for SciShow elsewhere on the internet? Facebook: http://www.facebook.com/scishow Twitter: http://www.twitter.com/scishow Tumblr: http://scishow.tumblr.com Instagram: http://instagram.com/thescishow ---------- Sources: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4812820/ https://wolf.org/wolf-info/basic-wolf-info/biology-and-behavior/communication https://www.semanticscholar.org/paper/Smiles-when-sharing-Mehu-Grammer/87014648ba7aeb73a5343527e056334d2c0254be https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437507 http://users.ox.ac.uk/~kgroup/publications/pdf/scharlemann_etal_2001_jeconpsy_smile.pdf