Can human hair be sewn onto a doll's head?
Yes,19th century fashion dolls (used in the fashion industry to showcase the latest designs before photography and other methods of advertising now taken for granted) had human hair that was also dressed in the latest styles from the acknowledged fashion centers for export to more distant regions...older one might be handed over to a very lucky (and probably rich) child once the styles were no longer the "first crack of fashion" (to use a term from the early 1800s) - but they were not playthings.
But it wouldn't be sewn to the doll's head if the doll had a china, bisque, or (later) plastic head - it would be made into a wig or (more recently) rooted in the scalp of the doll and then cut & styled. Only a doll made of fabric would have a head that could have the hair sewn to it the same way that a wigmaker might make a wig.
Human hair can be sewn onto a doll’s head. But, there are several types of materials used today in making life-like hair and some makers still use animal hair. The main difference in using synthetic hair and human hair is in the care of it. Human hair is great for a doll that you wish to make hairstyling part of the fun because human hair will only hold it’s style until it’s wet again. Synthetic hair bounces back into the style it was originally in every time it’s wet. So synthetic hair is best for dolls that won’t be spending time at the salon. It’s the same with human hair wigs for people. I occasionally wear a synthetic hair wig that is very similar to my natural hair. When it requires cleaning i simply wash, shake it out, and hang it or place it on “Lucy’s” head in the shower until it’s dry and when I’m ready to wear it again it’s already styled and requires only a little brushing. Lucy is, of course, my styrofoam wig head. What would really make a great doll for yourself or a loved one is using your own hair.