Human evolution; recent new modifications (Introduction)

by David Turell , Friday, September 13, 2024, 17:47 (69 days ago) @ David Turell

Studies of the median artery:

https://www.sciencealert.com/humans-keep-growing-an-extra-artery-in-their-arms-and-here...

"An artery that temporarily runs down the center of our forearms while we're still in the womb isn't vanishing as often as it used to, according to a study published in 2020 from researchers at Flinders University and the University of Adelaide in Australia.

"That means there are more adults than ever with what amounts to be an extra channel of vascular tissue flowing under their wrist.

"'Since the 18th century, anatomists have been studying the prevalence of this artery in adults and our study shows it's clearly increasing," Flinders University anatomist Teghan Lucas explained in 2020.

"'The prevalence was around 10 percent in people born in the mid-1880s compared to 30 percent in those born in the late 20th century, so that's a significant increase in a fairly short period of time, when it comes to evolution." (my bold)

"The median artery forms fairly early in development in all humans, transporting blood down the center of our arms to feed our growing hands.

***

"To compare the prevalence of this persistent blood channel, Lucas and colleagues Maciej Henneberg and Jaliya Kumaratilake from the University of Adelaide examined 80 limbs from cadavers, all donated by Australians of European descent.

"The donors ranged from 51 to 101 on passing, which means they were nearly all born in the first half of the 20th century.

"Noting down how often they found a chunky median artery capable of carrying a good supply of blood, the research team compared the figures with records dug out of a literature search, taking into account tallies that could over-represent the vessel's appearance.

"The fact the artery seems to be three times as common in adults today as it was more than a century ago is a startling find that suggests natural selection is favoring those who hold onto this extra bit of bloody supply.

"This increase could have resulted from mutations of genes involved in median artery development or health problems in mothers during pregnancy, or both actually," said Lucas. (my bold)

***

"'If this trend continues, a majority of people will have median artery of the forearm by 2100," said Lucas.

"This rapid rise of the median artery in adults isn't unlike the reappearance of a knee bone called the fabella, which is also three times more common today than it was a century ago.

"As small as these differences are, tiny microevolutionary changes add up to large-scale variations that come to define a species."

Comment: activities that require arm and hand use burn more calories than equivalent leg exercises burn. This would require higher blood flow. There are more hand activities now than in the past and thus the drive for more blood flow supplied. Noting my bold above, Lucas suggested gene mutations, and I wonder how many mutations are needed for this to happen in the 200 years span of this study. This is support for Shapiro's theory that DNA can be edited. An evolutionary example of adaptation, but not evidence of speciation, which is still a totally unknown process.