primate studies have consistently shown monkeys and chimpanzees have similar sex-based toy preferences as humans e.g., http://www.ncbi.nlm.nih.gov/pubmed/18452

primate studies have consistently shown monkeys and chimpanzees have similar sex-based toy preferences as humans e.g., http://www.ncbi.nlm.nih.gov/pubmed/18452921 http://www.ncbi.nlm.nih.gov/pubmed/18452921