So I went searching on Google to find out when people started smiling in photos.
One source said around 1930. By that time people had personal cameras and wanted photos of happy, smiling relatives. That sounds logical.
Then I read that the lower class peddlers were always smiling in photos, since smiles brought business from the richer classes. They were used to being nice and friendly to make a wage. That also makes sense.
Then I thought about having to stand and face the sun or a bright flash. That always made me frown.
What about the fact that in the beginning years of photography the apparatus was so slow that keeping a smile on your face for a couple of minutes was too long to endure?
As a former teacher, I can imagine that taking an official school class photo was so formal that no one was expected to be having a fun time. Have you taken a photo for an official document like a passport or driver's license lately? In The Netherlands your ears have to show and gosh knows what else. If you don't already look like a criminal when you go into the shop, you most certainly do on your photo.
After more Googling I discovered that people in Third World countries ( sure that is not PC--politically correct) rarely smile in photos. But playing children the world over are smiling. Thank goodness.
The nicest story about Helen Keller was when Anne Sullivan was trying to teach Helen to smile. If you never see a smile, can you possibly know what it is and how to do it?
Now I understand why we all look forward to a baby's first smile. At my mother's 87th birthday party a couple of weeks ago, my great niece B was our smiling baby. She has a lovely disposition and smiled the entire day. That was great for a 16 month old on a hot day in the country!