What is race?

I'll tell you one thing right up front, race is one hot potato of a topic.
But what is race, really? How is it defined biologically? In society?
I am a genomicist/geneticist and would like to note that it has actually been established that with the exception of genes for skin color or eye shape, etc, "race" is a social construct. As a society WE have attached other significances to these differences than the ones derived from their evolutionary advantages.
EVOLUTION DISCUSSION ALERT: These differences in most cases are based on evolutionary advantages conferred in the presence of a particular selective pressure–like too much sunlight. There have been studies that show that as prehistoric man migrated from Africa to Europe, skin color became lighter and this is believed to be related to the need for vitamin D which is derived from sunlight. The farther north you go the less sunlight per year and so the skin needs to have less melanin in order to absorb as much sun as possible. The converse is obviously true as well. Indeed as we take home our African babies we will find that they really need Vit D supplements to stay healthy in climates too different from the one they came from.
Back to social constructs: Unfortunately, they are as real as the genes in our DNA but in a different, more pervasive and thorny way. But they are definitely changing. When I was 6 in the 60s, there were really no biracial marriages or families to speak of. This has come a long, long way in my 40+ years. 40 yrs before that? You had segregation in every facet of daily life. Blacks and whites did not mix in any way.
I like to think we soon-to-be biracial families are helping that rate function. Every meaningful journey is made of individual steps. Societal change is slow but inevitable. Just like genetic evolution. But I do think the slope of that line is changing for the better. I think our kids will look back in 40 yrs and be astounded by how far, and how quickly, the change has taken place. I think they will be proud to have been at the forefront of that change. Will it be hard on us, and more importantly them? Yes. But it will also be very important and lead the way for these social constructs ending up in the evolutionary waste bin.
Lauren