If 40 years of age was old age during human evolution over the Pleistocene, what can it teach us - if anything - about how humans of 50, 60, 70 and older should eat, exercise and live their lives?
First a caution, drawn from limited personal experience. Just because a 50 year-old enjoys fresh bread, cheese, good wine and a sedentary lifestyle, this does not mean the experience of our evolutionary past is irrelevant. Sorry.
Even though 50+ year-old men and women may be older than the majority who have survived in the Pleistocene, there is fossil/skeletal evidence of older people having survived well past the age at which they would have been able to fend for themselves in hunting and gathering. Indeed, some of these skeletons show signs of arthritis and injury which would indicate that they would have been able to contribute only marginally to their group's immediate needs.
So, what caused them to be valued by the other members of the group who would have had to subsidize their existence for many years?
First, and most obviously, grandmothers can contribute to group well-being as patient, loving and highly skilled child-minders.
Secondly, older men and women would have had wisdom and knowledge to pass on about sources of food, especially in times of relatively infrequent climatic stress. The longer they lived, the more useful knowledge they would have accumulated and the more benefit that knowledge would be to the survival of their group.
Both men and women would also have been a repository of knowledge from fields such as religion, relationships, history and cultural survival. While I worked in the Highlands of Papua New Guinea in the 1970s I noted how the people had to work for only a few hours daily to survive quite adequately and how they spent more time in conversation and decoration than in simple food production. The transition of men from childhood to adulthood was a process which took years to progress through; the rituals became immensely complex and time consuming, merely because there was time to be consumed. Older women around Mt Hagen, for example, were inducted into a special arcane and highly metaphorical dialect of their own and became valued as the carriers of the knowledge of that essential aspect of their culture.
Thirdly, in the absence of evidence to the contrary, we can assume that the transition to old age was gradual and that both men and women would have remained economically active while they could contribute.
My conclusion, from a relatively youthful 55, is that middle age, at least, is still subject to the principles of personal health which we can learn from human evolution.
Scientists are now saying that ageing (as distinct from death) is not inevitable. Carruthers reports that research is moving on four fronts:
1. stem cell research
2. the use of powerful antioxidants to counter free radicals
3. genetic manipulation
4. the creation of drugs to mimic a calorie-restricted diet (CRAN - Calorie restriction with adequate nutrition) - so you can take a pill and eat what you want.
Other points from Carruthers's article are:
• 'The critical thing about longevity strategies is that it is best to practise them over an entire lifespan' (Prof Brian Morris, Univ of Sydney)
• Genetic manipulation of IGF-1 to reduce its impact on human growth hormone. Reducing IGF-1 extends life because it increases the body's resistance to internal stressors, such as free radicals. Tampering with IGF-1 upsets many biological processes. Reducing IGF-1 in experimental mice extended their lives, but reduced their fertility.
I welcome your input on this topic, particularly as it is vital to the policy debate in the more affluent polities about whether an aging population need, necessarily, impose a significant health-care burden on the rest of society.
Fiona Carruthers, review article 'The Elixir of Youth' in Australian Financial Review Magazine, February 2004
Page last up-dated 7 February 2004