Before you proceed, I would think that you may need to consider your input data. For example, you mentioned that the human population is represented as point data. A population value of say 5000 in and of itself may not provide enough information regarding population density. That is to say, over what area does the 5000 cover? If the population density information were available as polygonal data (for example, 5000 within the one city boundary, 2000 within the adjacent city boundary, etc), then one possible approach may be to do a simple overlay (IDENTITY) of the human population density onto the animal species point data. Then you could use this as a starting point in your analysis.