23 November 2016

Men are programmed to die before women

Female longevity has ancient evolutionary roots

Sofia Dolotovskaya, N+1

An international team of scientists has shown that the variability of life expectancy in a population during evolution leveled off as life expectancy in general increased. However, sexual inequality in life expectancy persists in humans to this day, despite the general increase in life expectancy. Article by Colchero et al. The emergence of long-lived populations is published in the journal Proceedings of the National Academy of Sciences.

Life expectancy in any population is described by two main characteristics: average life expectancy (which is usually estimated as life expectancy, or average age of death) and its variability. In the course of the evolutionary and historical development of man, life expectancy has changed very much. For example, in modern Japan and Sweden, the average life expectancy is high, and its variability is low: most deaths occur at the age of about 80–something years. Among primates, on the contrary, life expectancy is on average low (no more than 30 years) and at the same time varies greatly. For industrial societies, a correlation between these two factors was shown. The authors of this article decided to find out how the interaction of these two factors changed during the evolution of primates and, in particular, humans.

To do this, they analyzed life expectancy data for six primate populations and six human populations. The sample of primates included their main groups: lemurs of Madagascar, monkeys of the New World, monkeys of the Old World and great apes. The human sample included the main types of human societies: hunter-gatherers Hadza and Ache, the population of freed American slaves who emigrated to Liberia (in 1820-1843 had an extremely low life expectancy – 2 years!), as well as populations from Sweden in 1751-1759, Sweden in 2000-2009 and Japan in 2012.

It turned out that both in the course of primate evolution and in the course of human historical development, the variability of life expectancy decreased as life expectancy increased. In other words, the longer humans and primates lived as a whole, the smaller the spread of life expectancy became. There is a fairly simple explanation for this: when the average life expectancy is low, some individuals still live to old age, thereby increasing the spread of life expectancy values. The increase in the average life expectancy is mainly due to the survival of relatively young individuals, which leads to a decrease in this spread.

At the same time, the nature of the dependence of the total life expectancy and its variability turned out to be different for primates and humans, intersecting only at the level of pre-industrial human populations. That is, the industrialization of human societies has influenced the change in life expectancy much more than the entire evolution of human ancestors that preceded it.


The relationship of life expectancy and its variability in humans (gray line) and other primates (yellow line). The lines intersect at the level of pre-industrial human societies (hunter-gatherers). A drawing from an article in PNAS.

It also turned out that, despite a very strong increase in human life expectancy as a whole, the life expectancy of men still remains lower than that of women. This trend was also observed for primates: both among human populations and among other primates, women on average live longer than men, and the majority of centenarians are women. The results suggest that sexual inequality in life expectancy has deep evolutionary roots and is explained not only by social factors – for example, by the fact that women began to give birth to fewer children.

Over the past hundred years, the average human life expectancy has more than doubled and continues to grow. Previous studies have shown that an increase in life expectancy is associated with reading books in old age, a decrease in the number of children among women, as well as income levels. At the same time, the use of animal protein, on the contrary, was associated with a decrease in life expectancy. However, according to some scientists, such correlations work only up to a certain age, since, according to their calculations, the duration of human life cannot exceed about 115 years.

Portal "Eternal youth" http://vechnayamolodost.ru  23.11.2016

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