As anyone who has spent time with a newborn knows, babies are swaddled and be-diapered packages consisting of mucus, spittle, hiccups, and poop. With their ability to discharge seemingly any kind of liquid, it’s curious that they don’t actually produce tears when they cry.
According to Live Science, newborns can fuss and wail without making tears. To understand why, it helps to know why we make tears in the first place. Watery eye discharge appears when sadness, happiness, or other strong emotions provoke a fight-or-flight response, prompting our eyes to well up to better protect them from perceived harm. Tears also help us alleviate stress.
Infants' tear ducts are not fully operational at birth, however. They can cry and their eyes will get moist, but not enough tears are produced to result in noticeable dribbling. It’s not until three to four weeks after birth that babies are able to have full-fledged bawling sessions. In some babies, it can take up to two months.
You won’t be able to squeeze much sweat out of newborns, either. Eccrine glands that produce sweat on the body don’t gear up until shortly after birth, and for a period of time babies will produce sweat only on their foreheads.
Of course, babies can’t walk, talk, or digest solid foods, either. Getting them up to speed on human functions takes time. The only thing that seems fully operational from day one are their vocal cords.
[h/t Live Science]