Steven Pinker has written an excellent book here. I don’t properly understand the subtleties of his argument but he seems to be saying that a large part of who we are is inherent in our genes.
I don’t have any particularly strong feelings in the controversy such a position seems to conjure up. There is a strong body of intellectual opinion that has always decried any such argument as fascistic and racist (because it is said to suggest that people might actually be inferior (for a largely arbitrary value of superiority) by virtue of their genetics.
Pinker also notes that as our understanding of how the mind functions increases we will inevitably be slicing away at any concept of free will. Rationally speaking, there is no supernatural homunculus sitting in a Cartesian theatre in our pineal gland. Therefore our behaviour, what we would consider to be the product of free will and consciousness, is simply the result of chaotic interactions between the outside world and various areas of our brain.
Pinker himself offers a solution to these moral conundrum: view the scientific debate, in which human beings are mechanical objects, and the moral debate, in which all humans are afforded equal rights under the law, as two separate arenas of debate.
I agree with this: all men may not be created equal by virtue of their talents, skin colour, gender, financial security, and upbringing. But everyone is considered an equal and rational freely determined being under the law.