You could look at its glycosylation. One of the things that makes you unique as a human are your patterns of glycans on your cell surface. For example, only humans and a few other extreme rare out outliers produce sialic acid while all other animals produce hydroxylated sialic acid. The glycome tells you a ton about what species you’re dealing with. You can tell the difference between bacteria vs fungi vs monkey vs fish vs human cells by looking at their sugars alone.