Saturday, 10 October 2020

Continuing Human Evolution

Sketch of median artery vessel which supplies blood to the human forearm and hand.
Credit: Professor Maciej Henneberg
Forearm artery reveals human evolution continues – News

Three scientists from Flinders and Adelaide Universities, Australia, have found evidence of continuing human evolution in the increasing occurrence in adults of an artery known as the median artery, in the forearm. The median artery begins as the main blood supply to the developing forearm but normally atrophies in the embryo when the role is taken over by two other arteries - the radial and ulnar arteries.

In the 1880s, only about 10% of people were born with this artery; by the late 20th century it was around 30%, in people who died in the period 2015-2016 it was 33.33% and it is now at 35%. This shows that human evolution in respect of this artery has been faster in the last 250 years than at any other time in human evolutionary history. The occurrence of this artery is increasing so rapidly that the scientists calculate it will be be present in all people within 80 years if present trends continue. When it reaches over 50% it should no longer be regarded as unusual as its absence will be the normal condition.

The scientists's findings and statistical analysis of the data were published today in the Journal of Anatomy:

Abstract



The median artery has been considered as an embryonic structure, which normally regresses around the 8th week of gestation. However, various prevalences have been reported in adults since the 18th century. Furthermore, in a study by Henneberg and George (1995; Am J Phys Anthropol 96, 329–334), has suggested that increasing prevalence of the median artery during the 20th century was a ‘possible secular trend’. The present study, conducted nearly a quarter of a century later, is a continuation of that study. A total of 26 median arteries were found in 78 upper limbs obtained from Australians aged 51 to 101 years, who died in the period 2015–2016, a prevalence rate of 33.3%. Analysis of the literature showed that the presence of the median artery has been significantly increasing (p = .001) over time, from approximately 10% in people born in the mid‐1880s to approximately 30% by the end of the 20th century. The significance of the prevalence increased to a p value <.0001, when the results of the present study and other studies conducted by our research team were combined. After removal of the studies that were possibly biased, because of their specific focus on the evolutionary aspects of the median artery, the significance remained at p = .018. The present study provides an example of microevolutionary changes in the internal anatomy of the human body. Second‐order polynomial regression of the median artery's prevalence on dates of birth shows that it is now present in 35% of people and predicts that people born 80 years from now will all carry a median artery if the trend continues. When the median artery prevalence reaches 50% or more, it should not be considered as a variant, but as a ‘normal’ human structure.

Lucas, T, Kumaratilake, J, Henneberg, M.
Recently increased prevalence of the human median artery of the forearm: A microevolutionary change.
J. Anat.
2020; 237: 623– 631. DOI: 10.1111/joa.13224

© 2020 John Wiley & Sons
Other evidence of rapid human evolution in progress includes the disapperance of the wisdom teeth, the dissapearence by the end of the 20th century of an arterial branch off the aortic arch known as the thyroidea ima artery, increasing occurrence of abnormal connections of two or more bones in feet, the increasing presence of two small sessamoid bones (fabella) behind the knee and an increasing prevalence of spina bifida occulta (opening of the sacral canal).

The disappearance of wisdom teeth is continuing a trend which started in early hominin evolution when proto-humans discovered cooking which meant the wisdom teeth, normally used for grinding tough food, became redundant, allowing the lower face to become smaller and the cranium to expand to accommodate an enlarging brain. Most people still have them erupting as they approach adolescence, but they remain unerupted in some people and, because of the lack of space, often erupt at odd angles and may become impacted. In a supreme irony, a leading Creationist apologist, Ray Comfort, once wrote an article complaining bitterly about the pain he was suffering from impacted wisdom teeth and having to have corrective dentistry, not realising that his problem was caused by the incomplete evolution of his species and, in creationist terms, the poor design of the human face.







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