World wide people are living longer and average life span is projected to increase for many years to come with some countries already like South Korea and France passing the 90 years barrier (for women at least).
In my previous post I was keen to make the claim that senescent changes such as high blood pressure and increased blood pressure were adaptive responses to the physiological and cellular state we call senescence. What eluded me was any utility value of these changes other than the mere extensions of life span.
Life span data is created from population data which include figures for child mortality, fatal accidents and morbid diseases. Such pre-senescence deaths are markedly reduced in rich societies where modern levels of good nutrition, risk-reduction behaviours and medical interventions are prevalent.
Senescence or proper old-age, describes a state where morbidity clusters around conditions that are firmly age-related. These are heart and vascular failures, cancers and dementias.
Old age is more common than it once was, average population ages ‘in the wild’ as it were, rapidly return to a prehistoric forty-something, but being old is not a new thing. Human societies have always historically valued an elder as a repository of knowledge that the group has access to. Indeed to this day in South America unscrupulous loggers of the forest seeking to drive out native groups will kill the older tribe members knowing that the younger will fail to survive without their knowledge of how to live in a forest.
If it is important that some at least make it to old age, the ability for a group to produce sufficient elders would be from an evolutionary perspective subject to positive selection. Those groups that produced elders of value to them would be more likely to survive and thus the trait to produce useful elders would persist.
However elders are a burden as well as an asset. They cannot themselves effectively fight or forage but must be fed and supported. This means two things: one there must not be too many and two, their principal asset, their brain must be working to good effect. As referred to in the last post maintaining a low entropy functionality such as brain performance is energetically very expensive.
Regarding cognitive function, in this context recent memory and speed of thought are not of unique value, the young can do this better. However, memory of the past, if of one or more generation ago, is very valuable. A notable feature of the elderly is a loss of short term memory and an increase in clarity of their first thirty years. Many even severely demented elderly appear to return to their thirties, this much is well documented.
What if we are looking at an adaptive process? Senescence at a physiological and biochemical level is a distinctive condition, the body will recognise this. There is no reason not to assume that it will not adapt to it. What if the memory pattern above is not just ‘how it is’ but reflects the body’s attempt to preserve systems in a hierarchical, deliberate way?
The ‘last to go’ in order to keep your tribal value must be long term memory so as in my previous post, what if, increasing blood pressure and cholesterol absorption are the senescent body’s adaptive response to maintaining brain function?
I think they are and I suspect there are more medically ‘bad things’ for the risk factors of the middle-aged that are adaptations to aging. What if our medical and dietary responses to high blood pressure and high cholesterol combined with a near obsession with the consumption of antioxidants is simply wrong when elderly?
Long term blood pressure medication and statin medication are medical responses to big-data sets which essentially correlate their use with decreased mortality figures. Mortality from a common sense point of view is such a definitive measure of health that it finds few challengers as the No1 statistical marker.
But I would assert that it is not the best marker for the already elderly. Advanced medication could soon produce a generation of living dead with fragmented memories thus maximising their burden and minimising their value.
