For those of you who have somehow skipped 150 years of science: we have evolved from hominid apes. 2 Million years ago, these ancestors of ours enjoyed quite a short life of not more than 30 years – the same lifespan of chimpanzees today. But some 1,8 million years ago, our lifespan began increasing. And an evolutionary power factor came about; some people lived until the time of raising grandchildren. It was then grandparents who were there to help with the feeding and looking after the junior, thus improving the survival rate within a severe ambiance. This is the so-called “grandmother hypothesis.”
The problem is that, by a bad chance, we have inherited from our ape-kind ancestors a form of the gene that significantly increases the risk of mental deficiencies and heart diseases: АРОЕ4/4. This gene is responsible for transporting fats in the blood, and significantly influences development of patches in the vessels and deposition of toxic protein in the brain that consequently leads to Alzheimer. 1,8 million years ago we first had grandmas, but most likely they were a bit out of their minds. The recent form of said gene, which does not result in a condition, is the most common, and it came into existence just 200 thousand years ago.
Therefore, in the period between 1,8 million and 200 thousand years ago, both grandmas and grandpas were most likely forgetting everything all the time and passing away early. But exactly at that time, we started moving a lot when going far to run after or to gather food, thus exposing ourselves to aerobic stress. Aerobic activity is the strongest contributor to delaying aging in the brain and blood vessels in people who have the ancestral form of the АРОЕ gene.
Extensive research has shown that people with such genes are able to significantly decrease the level of cholesterol and defer senior-age mental disease by doing aerobic activity like jogging and daily physical exercise. Who knows, maybe this was the physical activity that made it possible for us to enjoy all the grandma benefits before the modern type of APOE gene came around.
Our closest living relatives, chimpanzees, have no new version of APOE gene. Thus, they do not live for a long time and do not bother themselves to do great aerobic activity. The species that we have taken over in terms of evolution, so called “Denisovan man,” as well had two copies the old useless APOE gene.
So it looks like no pain, no gain. And no grandmas, and therefore no us.