After reading this article Humans Alone See Brain Shrink With Age it makes me wonder if we need to do studies to see if those of us who eat a paleo diet are stuck in the same boat with those who eat SAD. Does a Western diet cause brain shrinkage or is it just a matter of being a human? Do we have any proof regarding the brain size stability among the Inuit or Masai?
The brain shrinkage would do a lot to explain the rampant dementia and Alzheimer's, wouldn't it? I would love to see a real study on this!
Aren't there any Paleo scientists out there that can put such a study together?
I had the SAME question on reading that study. I tried to find the original paper to see what people's they used but couldn't find it.
SO many times I hear a story about how "blah blah humans are like this" because they studied middle class American college students (that's who the grad students have access to!!) and came to a conclusion. Even when different racial or socioeconomic types are used, generally everyone studied is post-agricultural. We need to start getting Paleo types included in these kinds of studies!
Last winter I participated in a Vitamin D study on my campus... when filling out the "Diet over the past year" form I had to laugh... How many times a week do you eat - "granola" "white bread" "low fat white bread" "skim milk" "corn cereal" etc etc etc... I wonder if my mid-winter vitamin D status from eating lots of fish oil and beef liver threw off their results at all...
Here is the free full text of the study, it was only published online yesterday as an early edition:
It is interesting however it is hard to say if it is an effect of modern lifestyles or a general aspect of being human.
The chimpanzee in the study ranged from 10-45 years of age (40-45 is the average life-span of wild chimpanzees).
The humans in the study ranged from 20-88 years of age.
I don't think there is much brain shrinkage in our brains before the age of 45. It could be that the neurons in our brains are just not evolved to live as long as the rest of us. The older human subjects were assessed for their general health, so that none of them had a history of heart disease, hypertension, diabetes, or any other common age-associated disease. If average unhealthy older people had been included the degree of brain shrinkage may have been greater.
It would be interesting to compare people from different cultures or compare humans to other longer lived animals such as elephants or Galapagos tortoises that natrually live to 80+ years. It would be hard to get an elephant into a MRI scanner though...
"In humans, the compounded effect of a large brain with a metabolically expensive neocortex and a long lifespan appear to amplify the effects of cellular aging processes that are common to other mammals, resulting in more pronounced pathogenesis. Furthermore, these interactions may explain the unique vulnerability of human neocortical gray matter and hippocampus volume to such striking deterioration with age. Although an enlarged brain and extended lifespan have conferred decisive fitness benefits to humans, ultimately these adaptations come at a cost. These factors combine in the later stages of life to beset many of the elderly of our species with the effects of intensified neurodegeneration."
Doing the best we can to protect what we have got can't hurt through.
I'd be curious to see what it's like for brains of more stressed primates. My understanding is that Yerkes treats its primates very well, providing them with good environments and good food. I wouldn't be surprised if primates kept in more traditional lab environments exhibit this. I would be curious to study the Rhesus monkeys used in experiments like this http://www.nytimes.com/2009/07/10/science/10aging.html?adxnnl=1&adxnnlx=1311693979-JJ/jcTlQcbwoTvOimKqiOg
As far as data from hunter-gatherers it would be hard to get. There are hundreds of skulls to study, but an endocast can't tell you much about shrinkage. Only a brain or brain-scan would suffice and those are hard to get.
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