How similar are human brains within the same haplogroup? I've read about neuroscience and listen to talks like this one Juan Enriquez: Will our kids be a different species, I'm starting to realize that humans are not all the same, and are instead quite different.

My question is: how "different" are humans from each other from a point of view of neuroscience and neurobiology? 

One of the talks at TED.com gave a number that Homo Sapiens is 0.004% different from Neanderthal genetically. Another example given that olympic powerlifters have a certain genetic marker that the general population might not have. 

To refine the question: just how different from the perspective of white matter tract anatomy or the distribution of receptors within our neuronal populations are humans of the same haplogroup from one another?
The following comes from my research experience using fMRI to study the human visual system.

Overall, peoples brains are similar to each other on higher scales, and become very different from each other as the scale becomes smaller.

Differences between different people start with brain size and sulci patterns. Also male and female brain anatomies will be slightly different.

Wiring patterns within same brain regions will be similar between people, but as you get to individual neurons, it starts to look very chaotic. Dendrites will have stereotypical tree shapes for certain neurons (i.e. Pyramidal cells), but individual branches will be somewhat randomly distributed within their stereotypical areas.

As you get to the synaptic receptor/ion channel level, their distribution will be even more chaotic. Keep in mind the receptors themselves will behave stochasticaly, opening and closing based on when a particular ligand molecule binds to them.

The anatomical shapes of the brains will be mostly based on genes, so people within the same haplogroup should have brain anatomies slightly more similar than general population, but even those should have individual variations. Dendrite and receptor distribution generally depends on learning, so people with different initial conditions and environments during development will have dendrites wired differently.

I think the most fascinating aspect of these differences is that human minds are essentially slightly different neural networks that perceive the world in their own slightly different ways. The closer the genes and development environment between two people, the more similar will be their perceptions of the world.