As a species, survival is our only ambition. The only way that successive generations prosper is if they are a good fit with their environment and for them to survive long enough to create another generation. That is how our genes remain immortal.
Nature has two extreme methods to achieve this single aim. One way is to produce an enormous number of offspring and hope that a few survive to pass on their genes. Another approach – one followed by humans – involves having few children whom we look after until adulthood.
Being nurturing – protecting and supporting others – is our survival strategy, not competition. Nurturing involves having things to teach and living long enough to be able to teach them. Which is why humans live long and have such a big brain; the two go together.
It was some 1.6 to 1.9 million years ago that our brain grew very fast and some say – not without contention – that it mirrors the development of cooking. Cooking and making food more easily digestible resulted in more available nutrients for the hungriest organ in our body – our brain.
We can see how earlier hominids – versions of our species – lived longer as their head (and therefore their brain) grew bigger. Before then it was assumed that old age is irrelevant to nature.
Once we pass on our genes, we are no longer useful to nature. In some way, old age was contrary to nature because we have diseases that come out after we have passed on our genes.
Genes that show up in ageing – Huntington’s, Alzheimer’s, heart disease and many others – are passed on to our children because they do not show up until much later in life. Ageing hoodwinks nature. Because of this, the great biologist and Nobel laureate Sir Peter Medawar called ageing a “genetic dustbin”. Like the useless squeezed pulp of an orange whose juice has been extracted. But he was wrong.
Great biologist and Nobel laureate Sir Peter Medawar called ageing a ‘genetic dustbin’. Like the useless squeezed pulp of an orange whose juice has been extracted. But he was wrong
Mathematical models started to show greater predictive value when older people were included. Whether or not older people have a disease, their presence in the family predicted longer-living children.
For the vast majority of mammals in the wild, once they stop having the ability to reproduce, most die. Humans are different. We continue to live well past menopause, and this is because grandmothers have positive effects on the family.
In 2004, Mirkka Lahdenperä and her colleagues at the University of Turku, Finland, while examining the ‘grandmother effect’, found statistical evidence that a grandmother has a decidedly beneficial effect on the reproductive success of her children and the survival of her grandchildren. Older adult humans promote the survival of the species.
Unlike any other animal, we transfer wealth, capital and wisdom to our successive generations. Gene survival needs to include the broader community, the kin, the family. By 1973, John Maynard Smith and George Price introduced evolutionary game theory to this model.
While classic game theory requires players making rational choices on the basis of their individual gain, evolutionary game theory is based on acknowledging what others might do as well. Maynard Smith argued that evolution does not benefit individuals (since everyone dies), evolution is designed to benefit the species (or the community), so it is likely that the strategy that humans employ is based on benefits to the species rather than benefits solely to the individual. This insight was revolutionary. It transformed the argument from one where ageing is seen as a genetic dustbin to one where ageing becomes part of a package and where older adults contribute, in as yet unknown ways, to the survival of a population.
Despite this insight in 2002, 51 scientists recently published a position statement in Scientific American stating that “…ageing is a product of evolutionary neglect, not evolutionary intent.”
I am reminded of Einstein when confronted by quantum physics, who said that “God does not play dice with the cosmos”, and Niels Bohr responding with: “Einstein, don’t tell God what to do.”
We just do not know the intent of evolution. Ageing and having a big brain go hand in hand. It is nature’s plan for our survival.
A few minutes with older adults and the conversation quickly turns to their grandchildren. We are hard-wired for this role that nature has awarded us.
Congratulations, you made it.
Mario Garrett was born in Malta and is currently a professor of gerontology at San Diego State University in California, US.