When Was Gender Created?

Most animals are classifies by either male or female. Whether we are talking about fish, dogs, or humans, most of us are male or female (unless chromosomes get botched and there's an extra x or y chromosome). My question is, when did the two genders come to be, or how? Did animals produce assexually before?

Also, not to be rude, but I'm not looking for Adam and Eve answers. I am Catholic, but I'm looking for scientific explanations for a research poll. Thank you.