Mapping out what our species might look like in the future often leads people to think deeply about familiar things like height, brain size, and skin color. Yet subtle changes in our bodies today show how unpredictable evolution can be.
Take something as unusual as a blood vessel in our hands, which with today’s trends may become commonplace in just a few generations.
Researchers from Flinders University and the University of Adelaide in Australia said that the blood vessel that runs slowly inside our arms is still in the womb.
This means that there are more adults than ever before who have an extra nerve pathway running down their arm.
“Since the 18th century, anatomists have been studying the prevalence of this artery in adults and our research shows that it is increasing,” said Flinders University anatomist Teghan Lucas in 2020.
“The prevalence was about 10 percent in people born in the mid-1880s compared to 30 percent in those born in the late 1900s, so that’s a huge increase in a very short period of time, in terms of evolution.”
The central nervous system is responsible for the slow growth of all people, taking blood between our arms to feed our growing hands.
About eight weeks, it usually returns, leaving the work to two other vessels – the radial (the one we feel when we hit a person’s pulse) and the abdominal nerves.
Anatomists have known for a long time that atrophy of the central artery is not a guarantee. Sometimes, it lasts a month or more.
Sometimes we are born with them still pumping away, feeding maybe just the arm, or sometimes the hand as well.
To compare the spread of this continuous blood flow, Lucas and his colleagues Maciej Henneberg and Jaliya Kumaratilake from the University of Adelaide examined 80 legs from cadaver, all donated by Australians from Europe.
The donors ranged from 51 to 101 in passing, which means that almost all of them were born in the first half of the 20th century.
Considering how many times they found a chunky central artery that can carry a lot of blood, the research team compared the figures with the documents unearthed during the literature search, considering the readings that could represent the most representative of the vessel’s appearance.
Their results were published in 2020 Journal of Anatomy.
The fact that coronary artery disease appears to be three times more common in adults today than it was more than 100 years ago is a remarkable fact that suggests that natural selection is favoring those who pursue this extra blood supply.
“The increase could be due to changes in genes involved in the development of the central nervous system or health problems in women during pregnancy, or both,” said Lucas.
We can hypothesize that having a normal median artery would result in strong toes or strong forelimbs having reliable blood supply at birth. However, having one also puts us at greater risk of carpal tunnel syndrome, a serious condition that keeps us from using our hands.
Determining the types of factors that play a major role in the selection of a persistent central artery requires a great deal of ingenuity.
Either way, we’ll probably continue to see more ships in the coming years.
“If this trend continues, the majority of people will have a central artery in the arm by 2100,” Lucas said.
The rapid rise of the central nervous system in adults does not differ from the reappearance of the knee bone called fabella, which is found three times more today than a century ago.
Although these differences are small, small microevolutionary changes account for the large differences that come to define species.
Together they create new challenges for themselves, putting us on new paths to health and disease that we may find difficult to imagine today.
This study was published in Journal of Anatomy.
An earlier version of this article was first published in October 2020.