Remember alleles from Biology? Well, they are partly to blame for your resting bitch face.
According to Ozy, every person receives a pair of genes (no, not that kind) called the "serotonin transporter" - one from each parent. They can either be both long or short and sometimes even mixed. People with two short genes tend to laugh and smile easily than those with two long genes, who are likely to suffer from looking mad all the time. Others who have a mixture of genes have moderate expressions – nothing really out of the ordinary.
(Main image by Antonio de Moraes Barros Filho / Getty Images)