Here is further information regarding Neanderthals and how we may be able to determine the epigenetics which enables identical genes to create different physical features. They suggest that Alzheimers was new to homo sapiens. I have a theory that Alzheimers was a positive genetic development that caused elderly tribespeople to wander away when hungry, thus leaving more food for their children and grandchildren. I can imagine a tribesperson going out into a cold night to pee and then wandering off to look for food and freezing to death. My late husband’s greatest wandering took place when he was hungry, and while he still had strength and was not yet incontinent. I always had to urge him to keep me company in the kitchen, and feed him little nibbles while I rushed to get the meal on the table.
Interesting!
Good idea.
However, there are indications that protection against AD gave the humans an advantage:
Previous studies have linked two forms of the gene-CD33-to Alzheimer's disease. While one CD33 variant, or allele, predisposes a person to the disease, the other appears to protect against it by preventing the formation of protein clumps in the brain.
Both humans and chimps had similar levels of the damaging version of CD33, meaning it must be the more ancient of the two variants. However, when the researchers looked at the protective variant, its levels were four times higher in humans than in chimps. This suggests that chimps—which usually die around the time their fertility is coming to an end—have little use for the protective variant. Indeed, chimps don’t seem to suffer from the same type of cognitive decline seen with Alzheimer's.
http://www.sciencemag.org/news/2015/11/anti-alzheimer-s-gene-may-have-led-rise-grandparents
Here is more on Chimps and AD
http://www.alzforum.org/news/research-news/what-primates-can-tell-us-about-normal-brain-aging
I think marriage was the mutation that causes husbands to wander off ;-) (BTW and all joking aside, you are a saint to be taking care of yours)