by Roger Bourke White Jr., July 2006
I read an article in Science News this week which resonated with some of my thinking about evolution and the human condition.
The article in the June 24, 2006 edition was titled "Older but Mellower", and talked about how neuroscientist Leanne M. Williams of Westmead Hospital in Australia had done some studies of brain changes as a person ages. What she found was that there was an orderly change in how emotion was handled. As a person aged beyond 50 the processing of viewing pictures of people expressing different emotions shifted between the pre-frontal cortex (the very front of the brain) and the amygdala (a part of the central brain).
The details of the change are not important. What is important is that this is an orderly change that the brain undergoes when a person is 50 years old or older. The reason this is important is that it means evolution cares about 50 year old humans, cares even though they are no longer having children.
One of the basic premises of evolution is that what matters to the gene pool is survival. Another common premise is that whatever happens to an organism after its children are successfully reared doesn't matter to evolution, and this is why organisms that reproduce sexually, age. The premise is that a sexually reproducing organism trades off in favor of high performance in the growing and reproducing years, and doesn't care about what happens after that. That "doesn't care" is aging.
In the case of humans, this premise about sexually reproducing organisms appears to have been modified. It now seems that how grandpa's brain is organized affects how well grandson survives. This is so because the brains of old people undergo a well organized and standardized transition. This means that this transition is something programmed into human genes. And, if it's programmed into human genes, it means it has been selected for, which means it matters to human survival.
The sins of the father may be visited on the sons, but the benefits of a good thinking grandfather also bring blessings to the grandson.
The change in thinking is substantial in the sense that it is moving from one place to the brain to another distance place, which means that evolution has been working on this change a long time. This means that the change was beneficial to early Stone Age humans who lived tens of thousands of years ago, not just historical humans who lived five thousand years ago. It is likely that this ability to reorganize thinking was encouraged by the development of strong language skill because that's the vital skill in allowing a grandfather to influence a grandson's survival. And, this reorganizing of thinking would have enhanced the value of language skill.
It is truly impressive that evolution could pick up on such a subtle benefit -- grandparents being helpful to grandchildren in how they think -- and find a way to organize the gene pool to pass the benefit on through many generations.
... Truly impressive!
-- The End --