When imagining how our species could look in the future, it's common to get carried away with details like height, brain size, and skin colour. Even now, minor changes in our body show how unpredictable evolution may be.
Consider something as simple as an extra blood vessel in our arms, which, if current trends continue, may become commonplace in a few generations.
According to researchers from Flinders University and the University of Adelaide in Australia, an artery that runs down the centre of our forearms while we're still in the womb isn't disappearing as frequently as it used to.
That implies there are more adults than ever before who have an extra vascular channel running beneath their wrist.
In 2020, Flinders University anatomist Teghan Lucas remarked, "Anatomists have been investigating the incidence of this artery in people since the 18th century, and our work indicates it's obviously rising."
"When it comes to evolution, the prevalence was around 10% in people born in the mid-1880s compared to 30% in people born in the late 20th century, so that's a huge increase in a relatively short period of time."
Three major arteries in the forearm - median in the center. (ilbusca/Digital Vision Vectors/Getty Images)
| The median artery, which transports blood down the centre of our arms to feed our growing hands, originates quite early in the development of all humans. |
It normally regresses after eight weeks, leaving the job to two other vessels: the radial (which we can feel when taking a person's pulse) and the ulnar.
Anatomists have known for a long time that the median artery's withering isn't a guarantee. It may linger for another month or so in certain circumstances.
It may still be pumping when we're born, nourishing either just the forearm or, in some cases, the hand as well.
Lucas and colleagues Maciej Henneberg and Jaliya Kumaratilake from the University of Adelaide analysed 80 limbs from cadavers given by Australians of European heritage to compare the prevalence of this persisting blood channel.
On passing, the donors ranged in age from 51 to 101, indicating that they were nearly all born in the first half of the twentieth century.
The researchers recorded how often they came across a chunky median artery capable of delivering a good supply of blood and compared the statistics to records gleaned from a literature search, taking into account tallies that would over-represent the vessel's appearance. Their findings were published in the Journal of Anatomy in 2020.
The fact that the artery is three times as frequent in adults now as it was more than a century ago is a remarkable discovery that implies natural selection favours individuals who keep this extra bit of blood flow.
"This rise could have been caused by changes in genes involved in median artery formation, or health issues in mothers during pregnancy, or both," Lucas adds.
We could suppose that having a long-lasting median artery would provide a steady supply of blood to dexterous fingers and powerful forearms long after we were born. However, having one puts us at a higher risk of developing carpal tunnel syndrome, a painful ailment that limits our ability to use our hands.
It will take a lot more detective work to figure out what kinds of factors play a big part in the processes that lead to a persistent median artery.
Whatever they are, we are sure to see more of these vessels in the future years.
"By 2100, the majority of people will develop median artery disease of the forearm," Lucas said.
The reemergence of a knee bone called the fabella, which is also three times more prevalent today than it was a century ago, parallels the dramatic increase of the median artery in adults.
Small microevolutionary changes add up to large-scale variances that identify a species, no matter how minor they are.
Together, they produce new pressures, leading us down new paths of health and sickness that we may find difficult to envisage right now.
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