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Life expectancy by subnational division (or The Geography of Life Expectancy/centenarians)

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  • InquilineKea changed the title to Life expectancy by subnational division (or The Geography of Life Expectancy/centenarians)

Good article, with an extremely interesting hypothesis for the abundance of supercentenarians in Martinique and guadaloupe. The natural selection of the strongest, before reproductive age, by slavery. They also cite the apparent importance of genetics in Sardinia's supercentenaries. I've always been a supporter of the genetic hypothesis, alternative to the epigenetic hypothesis of the blue zones.


The slavery selection

The hypothesis

The validation work remains to be completed. It can still be improved upon in Guadeloupe and the fieldwork is pending in Martinique. However, it is already certain that additional investigations will not be able to bridge the gap between 3 supercentenarians per 1 million people observed in metropolitan France versus 21 in Guadeloupe and 24 in Martinique. Undoubtedly, the extreme prevalence of supercentenarians in the two French Caribbean islands is real, and it is not too soon to seek explanations. Although such a huge task obviously cannot be completed here, it is at least possible to discuss some hypotheses and hopefully inform their probability by means of some observations.

When speaking with experts in the field of longevity research, many ascribe long lifespans to either climate or dietary habits. Indeed, this type of explanation is often given for cases like Okinawa in Japan, Crete in Greece, and the so-called blue zones identified in various other places by Michel Poulain (Poulain, Herm & Pes, 2016). However, genetic reasons are also sometimes suspected, such as in Sardinia (Poulain et al., 2004). As explained by Thomas Pearl (2008), lacking genetic variations that predispose to disease as well as having variations that confer disease resistance (longevity enabling genes) are probably both important to achieving exceptional old age. It seems to me that the cases of Guadeloupe and Martinique require paying particular attention to genetic causes. First, the extreme prevalence is much higher than in any other cases, and it is difficult to imagine that only environmental factors could explain such a gap from “normality.” However, the historical settlement of these territories also opens the door to a reasonable hypothesis for strong genetic factors. The current populations in Guadeloupe and Martinique are largely descendants of slaves. Indeed, at the time of abolition (in 1848), the proportion of slaves and freedmen was more than 90% compared to less than 10% “whites.” Today, proportions for the descendants of these two populations is unknown, but it very likely has not changed much, due to low immigration and high fertility among black people compared to white. Thus, one can assume that the majority of the population has inherited the genetic characteristics of former populations who were strongly selected by the very severe over-mortality experienced by their slave ancestors. In particular, their capture, confinement before deportation, and crossing of the Atlantic were extremely deadly. Then, upon arrival in the Antilles, these usually quite young people were subjected to forced labor and brutal treatment. Many still died before having children. The entire process produced severe selection of the strongest individuals, who were the only ones that managed to have children. If there is a link between robustness and longevity, this could be sufficient in explaining the extreme prevalence of supercentenarians there today.


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As a matter of fact, the exceptional longevity occurring in the Sardinian Ogliastra province might in part be explained by the natural selection imposed by the tough living conditions in such a poor and isolated rural area. In other words, the survival of the strongest was the rule. Illnesses and sometimes starvation brutally meted out infants not strong enough to survive. A strain of genetically exceedingly resilient people emerged, which did not mix much with the external world, due to isolation.

Food, exercise, and all the rest might also have played a part of course, but I strongly doubt these are the governing factors.

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