Please don't take this personally but as an anthropologist with an interest in human evolution I feel the need to nip these old neuroscience myths in the bud. The lizard brain theory dates back to the 60's and is no longer accepted by modern neuroscientists. It's also not possible for humans to have inherited physical traits from wolves, because evolution is descent with modification, and canines are not the ancestors of humans or primates in general. The modern taxonomic classification of an organism is also the evolutionary history of that organism, and when we compare humans with wolves, cats, foxes (chosen because they're the most common therian otherkin I see around), humans come from the order Primates while the latter all come from the order Carnivora. Humans can't have inherited physical traits from Carnivora because they don't descend from Carnivora.

By this evolutionary logic, primates should be the most common form of otherkin, but that isn't what we see, and I also don't think an evolutionary/neuroscience explanation for otherkin is necessary. In fact animals that are culturally significant in the english speaking world such as wolves, cats, foxes seem to be the most common, so I think a cultural explanation for otherkin is most likely, and doesn't invalidate them in any way. Plurality is also a culturally shaped experience!

The left brain/right brain theory also seems to be a myth according to modern studies.

--Janusz