The appendix ensures an increase in longevity in mammals which result from it

The appendix ccal or more’appendix publicly called the appendix was considered since the work of Charles Darwin as a dress structure, useless if not dangerous of the risk of its inflammation observed in humans which can lead to death in the absence of treatment. Recent research has challenged this idea by showing that the appendix first appeared in mammals at least 80 million years ago and makes multiple and independent appearances with no obvious correlation with diet, social life, ecology or the size of the cecum. Already since Charles Darwin, we knew that Homo sapiens was not the only mammal to have an appendix and gradually, as the anatomical dissections proceeded, the data became clearer. We now know that species as diverse as the Orangutan, the Koala, the Lament, the Beaver or even the Platypus are all learned from this intriguing anatomical structure. However, the functions conferred by the appendix still remain enigmatic.

During our study, we discovered, by analyzing data from 258 species of mammals including 39 with and 219 without appendages, that the presence of this anatomical structure is correlated with an increase in longevity observed for the species, regardless of the weight of the evolutionary covariance. This is the first demonstration of the existence of a correlation between the presence of the appendix and a trait in the history of mammalian life. To be able to interpret this result, it is interesting to note that the theory of the evolution of aging known as Williams predicts an increase in the longevity of a species in the event of extrinsic mortality (predation, infections, diseases, etc.) is reduced.

This theory has been questioned on various occasions, but recent comparative studies have confirmed its validity in taxa that experience age and density dependent mortality, such as mammals. Thus, the appendix must contribute to the increase in longevity by a reduction in extrinsic mortality defined as mortality directly suffered by causes external to the organism. By its shape and composition, the appendix would be a selective bacterial sanctuary which should decrease infectious mortality by promoting the rapid and selective recolonization of bacterial species essential to the host.

This hypothesis is one of the most plausible hypotheses explaining the decrease in extrinsic mortality and therefore the prolongation of longevity in mammals with an appendix. However, other hypotheses coexist as to the functions of the appendix, and our possible results are of great help in answering this controversial question of the function of the appendix. In addition, we show that the appendix has appeared at least 16 times and has only been lost once during the evolutionary history of mammals, an evolutionary asymmetry very in favor of gain which validates the idea that the appendix confers by its function a significant positive selective advantage with regard to the laws of natural selection.


Publication : 

The cecal appendix is correlated with greater maximal longevity in mammals

Maxime K. Collard, Jérémie Bardin, Michel Laurin & Eric Ogier-Denis


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