Even if it matters whether or not humans and animals are similar, humans and animals are in fact similar enough that both should be granted rights.  We have already noted that beings do not need to be similar in order to be equally morally considerable. Assuming but not conceding that this is false, we will prove that animals are in fact incredibly similar to human beings, so much so that we should grant them rights.  First of all, animals have an equal capacity to experience pain. While we are unable to know exactly what other humans or animals are experiencing, we can make inference from what we observe. According to Peter Singer: “Nearly all the signs that lead us to infer pain in other humans can be seen in other species...The behavioural signs include writhing, facial contortions, moaning, yelping or other forms of calling, attempts to avoid the source of pain, appearance of fear at the prospect of its repetition, and so on”. [1]  In addition we know that animals have nervous systems very like ours, which respond physiologically as ours do when the animal is in a circumstance in which we would feel pain—an initial rise of blood pressure, dilated pupils, perspiration, an increased pulse rate, and, if the stimulus continues, a fall in blood pressure. Although human beings have a more developed cerebral cortex than other animals, this part of the brain is concerned with thinking functions rather than basic impulses, emotions, and feelings. These impulses, emotions, and feelings are located in the diencephalon, which is well developed in many other species of animals, especially mammals and birds.” Animals therefore have the capacity for physical and emotional suffering, and so should be granted rights.  [1] Singer, Peter. "All Animals are Equal." Ethics for Everyday. (Benatar, D Ed.) McGraw Hill: New York. 2002