These are pictures of my two grandmothers, my mother, and me at age 11.
Do you have family photos where the people are smiling, and some where they're not? I wouldn't be surprised if someday someone creates an app that can take a picture of someone not smiling, and through forensic-type regeneration algorithms morph the picture into a picture of the same person smiling and have it look natural. Probably not taking into account bad teeth, or no teeth...but surely our ancestors did smile! They were human after all. Mine were, anyway, ha, ha. (not Fish - I married into Fish)
Here is a TEDTalk on smiling. It is very interesting.
Take pictures of the people you love - smiling, and cherish those memories. We smile from our memories, and from our thoughts and our feelings. Maybe purring is for cats as smiling is for us. I smile when my cat purrs. He's here now. Do you have family photos that include family pets?
Smile posts - How many times have you said of someone in your family, "Oh my, they've got So&So's smile"? You can see smiles pass down through families and generations.
What was Mona Lisa's inside family joke?