Imagining how our species may appear in the distant future often invites wild speculation about prominent features such as height, brain size, and skin tone. However, subtle changes in our anatomy today demonstrate the unpredictable evolution.
Take us something as mundane as an extra blood vessel in our arms, that following current trends could be a commonplace in a few generations.
According to researchers at Flinders University and the University of Adelaide, Australia, an artery that runs temporarily through the center of the forearms while we are still in the womb does not fade as often as before.
This means that there are more adults than ever before which means an additional vascular tissue channel flowing below the wrist.
“Since the 18th century, anatomists have been studying the prevalence of this artery in adults and our study clearly shows it increasing,” Flinders University anatomist Teghan Lucas said in 2020.
“The prevalence was around 10 per cent in people born in the mid-1880s compared to 30 per cent in those born in the late twentieth century, so this is a significant increase in a quite a short period of time, in terms of evolution. “
The middle artery forms quite early in development in all humans, carrying blood through the center of our arms to feed the growing hands.
Three main arteries in the forearm: middle in the center. (ilbusca / Digital Vision Vectors / Getty Images)
At about eight weeks, it usually recedes and leaves the task in two other vessels: the radial (which we can feel when we take a person’s pulse) and the ulnar arteries.
Anatomists have long known that this fading of the middle artery is not a guarantee. In some cases, it stays for a month or so.
Sometimes we are born with it still firing, feeding only the forearm or, in some cases, the hand as well.
To compare the prevalence of this persistent blood channel, Lucas and colleagues Maciej Henneberg and Jaliya Kumaratilake of the University of Adelaide examined 80 corpse limbs, all donated by Australians of European descent.
Donors went from 51 to 101 as they passed, meaning almost all of them were born in the first half of the 20th century.
Noting how often they found an average thick artery capable of carrying a good blood supply, the research team compared the figures with records taken from a literature search, considering sizes that could overly represent the appearance of the ship. Their results were published in 2020 at Journal of Anatomy.
The fact that the artery appears to be three times more common in adults today than it was a century ago is a startling finding that suggests natural selection favors those who are left with this bloody supply.
“This increase could have been a consequence of mutations in genes involved in the development of the middle artery or health problems in mothers during pregnancy, or both in reality,” Lucas says.
We could imagine that having a persistent middle artery could give strong fingers or strong forearms a strong blood boost long after birth. However, having one also carries a higher risk of carpal tunnel syndrome, an uncomfortable condition that makes us less able to use our hands.
If the types of factors that play an important role in the selection processes of a persistent middle artery are described, much more attention will be needed.
Whatever it is, we are likely to continue to see more of these ships in the coming years.
“If this trend continues, most people will have the middle forearm artery by 2100,” Lucas said.
This rapid increase in mean artery in adults does not resemble the reappearance of a knee bone called a fabella, which is also three times more common today than a century ago.
However small these differences may be, small microevolutionary changes add up to large-scale variations that come to define a species.
Together they create new pressures themselves, placing us on new paths of health and disease that can now be hard for us to imagine.
This research was published in Journal of Anatomy.
A version of this article was originally published in October 2020.