It all depends upon exactly what you mean by "define our humanity." This is the nomenclature of classic philosophy. To the classical philosophical query, the answer is that technology does not at all change how we define our humanity. The definition of our humanity still revolves around being rational, reasoning entities with compassion and dignity that is bound up in our ability to see from other points of view and embrace that which is at variance with ourselves.
This is a question that can be answered in many different ways. Moreover, whenever we seek to define something, especially something as complex as humanity, there will be many different answers.
With the advances in technology and science, we are increasingly defining ourselves through science. We are seeing ourselves as mechanisms. We want to know how the human body works and manipulate it for our own benefit. For example, the advancements in the human genome project are startling. The hopes of this project will be to know the human DNA so well that it will be able to prevent and treat all sort of diseases. Another example of this point is the idea of human cloning. A less dramatic example is plastic surgery.
Through science and technology, we are trying to master humanity, as if it is organism that can be manipulated. I am not saying all these advances a bad (far from it), but we are close to playing the role of God. There are certain ethical ramifications. Moreover, we run the risk of cheapening life if we go down the path.
I believe that humanity has changed because of science and technology, primarily by means of the availability to almost everyone on the planet of instant communication. A protest on Wall Street is seen by the world within minutes of its start. Flash mobs can be organized in minutes or hours. The death of Khadafi is instantly witnessed worldwide.
Here is how humanity has been changed: We are no longer a world of multiple cultures unaware of and unsympathetic to one another. Instead we now have a oneness that encompasses what humans are, living beings struggling to survive and thrive, all sharing a need for love, nurturing, protection by our government, and freedom from hunger, oppression and neglect.
In today's world of science and technology, totalitarian governments cannot survive (as we have recently seen in the Middle East).
Every person has a different view of humanity, whether it be the ability to reason abstractly or rationally, or speech, or tool use... science and technology come from our ability to reason, and become tools of our imagination. We are limited only by what we understand, and as we learn more about the inner workings of the world, we develop a greater capacity to form and change it at will. We may find this to be a power struggle, as we waver between exploiting science just because we can, and being cautious because we just don't know how much damage we can do.
The increase in scientific knowledge and technology over time has led us to redefine key aspects of what it is to be human. We live longer, and this has redefined the family and our expectations in everything from work to retirement. It has led us to ask questions about the quality of life vs. the quantity. We have been able to cure major diseases and successfully limit others. We have been able to produce more food.
At the same time, we have the capacity to end all human life in a short period with fearsome weapons and viruses. So we have a strange dichotomy about this subject, where we seem to pursue technology in part to enhance the human existence, and in other ways we pursue it for profit, and at our own peril.
Darwin's theory of evolution doesn't disprove my personal Christianity. I am continually awestruck by the magnificent creation that God put into motion and the intricacy with which it has evolved. I think expanding scientific knowledge doesn't define humanity - it adds to our base of knowledge and supports further exploration. I do have real concerns about how we will deal with some of the moral and ethical decisions that are going to need to be faced as technology and medical science, in particular, advance further into realms of cloning, genetic selection, etc.
I would like to build on #6 by saying that this process was something that began, or at least we can clearly see occurring, during Victorian times with the massive increase in scientific knowledge and the way that Darwin's theory of evolution seemed to disprove Christianity. This epoch had a massive impact on religion and faith, as science was thought by many to have "disproved" religion. I do agree that as science and technology continue to make ever-bewildering advances, our humanity and our identity, how we define ourselves, will change accordingly.
I like the point that #5 raises, but I would argue that science and technology have moved us towards defining our humanity in the way (rationality, reasoning) that she suggests. The more science and technology we get, the more we feel this way.
This takes us away from defining our humanity in terms of God and religion. Before we had so much science and technology, we were more likely to see our humanity as a gift from God or to define it as the fact that we were made in God's image. In that sense, our increasing scientific and technological abilities have changed the way we define our humanity.
In the science fiction realm, the more artificial intelligence we develop the more complex humanity will become. Cloning is another example. If we clone a human, does that person have the same rights to be human? If we built a robot that can think for itself, what rights does it have?
Our ability to quickly communicate through a variety of media is affecting our humanity. In recent decades past, just the television and telephone had the remarkable ability to unite us. Now we have multiple ways to have almost constant and instant contact with people -- family members and complete strangers. We can follow people on Twitter; we can look people up on the Internet; we can "friend" people on social networking sites. All of this interconnectedness is changing the way we behave, the choices we make, what influences us, and how we treat and talk to people.