What is a human being?

In class recently we watched Star Trek: Then Next Generation because different concepts that we have been discussing in class appeared in the television series. In this episode, Data an android that works on the spaceship enterprise essentially is told by command that he has no rights. The captain and the other members of the enterprise argue that Data does in fact have rights equivalent to a human even though he is a machine. Now this argument seems like something that is far fetched and never will materialize. However, with numerous people working to achieve artificial intelligence we can not rule the possibility that we will face this problem in the future. The question that needs to be addressed is what makes a person human? This question has been redefined numerous times throughout the ages. In America before the civil war African Americans were thought as property and therefore subhuman. In Germany this thought occurred during the time of Hitler when Jews were disposed of like garbage. However, none of these concepts are actually true despite how much people thought of African Americans as their property or Jews as trash they are still human and therefore endowed with certain rights. But again what makes us human? Is it our anatomy, our DNA, our thought process, or our emotions? It is hard to define a person based on their anatomy. Not all people have the same physical features…some people are born without hands, arms, sights. Are these people human? Some people have more than 23 chromosomes. Some DNA is altered and people can have defects where they have 23 and a ½ chromosomes. As far as our thought process not all people think the same way and there is differing degrees of thought. As far as emotions are concerned, people do not always show the same emotions to every experience. I also recall a medical documentary in which a girl in elementary school could not smile or frown. Although she may have been happy no one could tell. This became obvious when the DJ at the party asked why she was not happy and smiling like her sister. As far as I am concerned it is hard to discern what can be classified as a human being and given rights. So should not everything that has thought be treated as if it has some intrinsic value and is not just a mean to an ends?