We all start life as sociopaths.
Babies don't much care that mommy is dead tired from getting up every two hours to feed them. Their cries say it all: "Feed me. Change me. Hold me. Meet my needs."
Fortunately, we are also hardwired from the beginning to be interested in other human beings, to gain pleasure from seeing a face we recognize, from hearing other human voices. When a toddler reaches out from her high chair to offer her mother a bite of the cookie she is enjoying, wishing Mommy to experience the pleasure she has, we are certainly seeing the beginning of empathy.
In fact, I believe we are hardwired as humans to become empathetic, that caring about others and wanting to understand others is a survival trait for the human species. We are a social species, and we have succeeded spectacularly because of this.
But, there are aberrant individuals in any species. In humans, a severe lack of empathy leads to a sociopathic personality--a person who has no interest in the experiences or feelings of any other human being but himself. What are the worst human beings in our history but sociopaths, able to commit mass atrocities because they are unable to feel the pain they are causing others, unable to even perceive others as full human beings like themselves?
And of course, empathy runs on a continuum, like most things. It's not either/or: either you're empathetic or you're a sociopath. Most of us fall somewhere between Mother Teresa and Hitler.
We all know people who just don't seem all that interested in anyone but themselves. This person, when you tell him you just had something bad happen to you (let's say you found out your mother has cancer), responds with his own story of someone he knows who had cancer, or a story about an illness his own mother had, rather than responding to you and your experience. Sure, sometimes people do this as an attempt to let you know that they understand where you're coming from. But you know the kind of person I mean: whatever you say, their response starts with the word "I". They're not quite up to the mid-point on the empathy scale.
On the other hand, we all know someone who seems genuinely interested in hearing about us and our feelings and experiences. This person's response tends to be a question about you and what you said: "Oh my, I am so sorry to hear that. What's your next step with your mother? How's she taking this? How're you holding up?" These people really share your joys and your sorrows, and they make the world a better place.
Yes, we all start life as sociopaths. Fortunately, most of us naturally learn to become empathetic to others. Helping all children to increase their empathy for other people, including people not in their own social group (ethnicity, religion, culture, etc.), would be a huge boost in moving our human species to a higher level of existence. This is especially true for children who have not themselves experienced an empathetic response--those children who are abused, who are unloved. Teach a child empathy, show a child empathy, and we will all be better for it.