Or nematodes, if we're confining it to animals. They're everywhere.
And I do mean everywhere: http://plpnemweb.ucdavis.edu/nemaplex/FerrisPublications/pdf files/165Ferris2009.pdf
But I basically agree - the only way I'm aware of that humans could be said to be objectively 'superior' or 'dominant' thus far is brain complexity (and factors resulting from that) - so the only way a 'soul' could be unique to us is if it's a factor of that complexity (see above!
).
And I do mean everywhere: http://plpnemweb.ucdavis.edu/nemaplex/FerrisPublications/pdf files/165Ferris2009.pdf
But I basically agree - the only way I'm aware of that humans could be said to be objectively 'superior' or 'dominant' thus far is brain complexity (and factors resulting from that) - so the only way a 'soul' could be unique to us is if it's a factor of that complexity (see above!