Posted on 10/09/2020 11:03:16 AM PDT by Red Badger
Picturing how our species might appear in the far future often invites wild speculation over stand-out features such as height, brain size, and skin complexion. Yet subtle shifts in our anatomy today demonstrate how unpredictable evolution can be.
Take something as mundane as an extra blood vessel in our arms, which going by current trends could be common place within just a few generations.
Researchers from Flinders University and the University of Adelaide in Australia have noticed an artery that temporarily runs down the centre of our forearms while we're still in the womb isn't vanishing as often as it used to.
That means there are more adults than ever running around 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," says Flinders University anatomist Teghan Lucas.
"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."
The median artery forms fairly early in development in all humans, transporting blood down the centre of our arms to feed our growing hands.
Three major arteries in the forearm - median in the centre
At around 8 weeks, it usually regresses, leaving the task to two other vessels – the radial (which we can feel when we take a person's pulse) and the ulnar arteries.
Anatomists have known for some time that this withering away of the median artery isn't a guarantee. In some cases, it hangs around for another month or so.
Sometimes we're born with it still pumping away, feeding either just 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 from the University of Adelaide examined 80 limbs from cadavers, all donated by Australians of European descent.
The donors raged 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, they 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 favouring 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," says Lucas.
We might imagine having a persistent median artery could give dextrous fingers or strong forearms a dependable boost of blood long after we're born. Yet having one also puts us at a greater risk of carpal tunnel syndrome, an uncomfortable condition that makes us less able to use our hands.
Nailing down the kinds of factors that play a major role in the processes selecting for a persistent median artery will require a lot more sleuthing.
Whatever they might be, it's likely we'll continue to see more of these vessels in coming years.
"If this trend continues, a majority of people will have median artery of the forearm by 2100," says 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.
Together they create new pressures themselves, putting us on new paths of health and disease that right now we might find hard to imagine today.
This research was published in the Journal of Anatomy.
Juvenile nutrition greatly affects height.
https://www.theguardian.com/science/2002/feb/03/genetics.research
(Is human evolution finally over?
Scientists are split over the theory that natural selection has come to a standstill in the West)
It’s not even darwin-ism. It can’t be.
No one is going through natural selection because of an extra artery in their fore-arm. No one is surviving better because of it and no one is having more babies because of it. It probably has more to do with change in the diet and nutrition of mothers during pregnancy over the last several centuries.
Easier to sneak into a house when you are of a slight build.
In the future we will ALL throw a baseball at 150 MPH.
When I was young I held a job for a time in a building that was constructed around 1870. I am 5’ 9” and I had to duck to get through most of the doorframes.
I went to Jamestown settlement in Virginia when I was about 12. We went on board the ships that the settlers rode on from England. I had to duck to get around below decks. The tour guide told us that most of the people back then were all about 5 foot tall.
On a whole I agree with you that people were shorter.
However this “data” probably is not representative.
I imagine these people grew up under very tough conditions, probably lacked nourishment during their growing years. So this group being “stunted” in large numbers is not surprising.
Especially Custer. He was a whack job.
“It probably has more to do with change in the diet and nutrition of mothers during pregnancy over the last several centuries.”
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I once had someone tell me he knew evolution had to be true because people were getting taller - really. I had to explain how diet and nutrition works to him. He was a high school teacher - and of course, a devoted liberal.
terrible nutrition.
“In the future we will ALL throw a baseball at 150 MPH.”
—
Our great great-grandchildren will be 20 feet tall, thanks to Chuckles Darwin. If the NBA ever goes back to normal, the games of 2050 should be amazing.
Any natural selection happening here?
That is genetic selection. Not evolution.
No genetic information is being added.
Not evolution. Its not new, just not regressing as commonly as before.
Might be beneficial, and still not evolution; no new genetic material that is favorable that wasn’t there before. Like a human with night vision.
God put it there.
Epigenetics is a reasonable to answer to what we are seeing. Thanks for reminding me of that.
It seems like those living in their parents' basement playing Nintendo would be less likely to pass on their genes. :-)
Maybe the medial artery helps raising the middle finger.
Agree. Let me know when someone grows wings.
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