In Body by Darwin I argue that Alzheimer's disease is a disease of neurons and synapses, not amyloid and phosphorylated tau protein. Here the researchers identify 6 genes that they have evidence were strongly selected for 50,000 and 200,000 years ago (approx.). Here's a quote from the Nature piece: "The study finds evidence that 50,000 to 200,000 years ago, natural selection drove changes in six genes involved in brain development. This may have helped to increase the connectivity of neurons, making modern humans smarter as they evolved from their hominin ancestors. But that new intellectual capacity was not without cost: the same genes are implicated in Alzheimer's disease." It seems the central idea is the metabolic cost of running hot brains finding its repercussions in AD.
Here's a link to the journal where there is open access PDF download.