Is anybody… is… is anybody gonna… No? Okay. I’ll do it then.
Okay, see, this is like 94% bullshit. I mean, it’s about 6% science, yes, but it’s also 94% bullshit.
First things first, “you are a product of evolution”. What. Every organic thing on the face of the planet is a product of evolution. Evolution kicked off somewhere around 3.8 billion years ago with the first appearance of life and it hasn’t really stopped since. Everything that came before you was “a product of evolution”. That phrase doesn’t mean anything special.
But Bear, you say, it means people without the thing are just more highly evolved than those who have it!
Bullshit, I say. There is no such thing as “more highly evolved.” Evolution is not some kind of mad rat-race to see which lineage makes it to the top of Darwin Mountain first. Evolution is about creating an organism that can survive and reproduce as effectively as possible to fill a particular niche or role in its given ecosystem.
How good are you at burrowing in the dirt and eating leaf litter? You probably suck at it. But roly-polies (aka, sowbugs, pillbugs, or terrestrial isopods) are great at this! Is a roly-poly less evolved than you because it doesn’t drive a car and use the internet… or are you less evolved than a roly-poly because you can’t break down leaf litter into small, usable particles? The answer is neither–you’re both beautifully evolved organisms filling different niches in the ecosystem and doing it very well.
Now, so far as this “muscle” (it’s actually a tendon) being “slowly erased from our genetic code”… no.
Let me start out by saying something that really should have been said in the first place, because it’s a cool bit of knowledge to have and it’s fun to say: The tendon shown in the picture is called the palmaris longus. Palmaris longus! Say it out loud!
The palmaris longus is what is known as a vestigial tendon. When something is vestigial, that means that it’s no longer needed by the organism, but isn’t doing enough harm by being there that it impacts the organism’s ability to fill its niche and reproduce. A vestigial organ or body part neither helps nor hinders the organism; it’s just kinda there, a relic of eons past.
(For example, the tail of a bear. A tail is utterly useless to a bear–it is too short to provide any kind of stability while in motion, isn’t prehensile, and doesn’t play a role in body language–but they still have ‘em.)
Now, it’s true that vestigial traits have a tendency to disappear over time, but not because they’re being erased from the genetic code.
Evolution–hell, natural selection–depends on there being inherent variation among the population. If one individual has a variation that gives it an advantage, and said variation is genetically determined, there’s a slight chance their offspring will inherit that useful variation. Slight. Conversely, if one individual’s variation is a disadvantage, it may hinder its chances of reproducing, and thus prevent it from passing that unhelpful trait to the next generation.
But a vestigial trait, which confers no advantage or disadvantage, is sort of stuck in limbo and is only passed along by pure chance.
I’ve heard people say, for example, that wisdom teeth are “evolving out” of the human species, and it makes me want to throw mine–which were surgically removed when I was 18–at their faces. That’s not how evolution works. In order for a trait to “evolve out” of a species, it has to be selected against. It has to be obvious so that other members of the species can notice it and find it unsexy enough that they won’t mate with the individual displaying it.
Do you only date people who never developed wisdom teeth, in the hopes that any offspring you have with them will also never develop wisdom teeth? I’m thinking not. There’s no active selection against the wisdom tooth trait. If anything, there’s selection for the more refined, narrow jaw structure that separates our skulls from those of like every other ape on the planet (which coincidentally is why most people don’t have space in their jaws for a third set of molars to properly develop and erupt, and need their–frequently deformed–wisdom teeth extracted), and that may in turn be linked to whether or not wisdom teeth form.
Wisdom teeth, like the palmaris longus, are a vestigial trait that is being passed along purely by chance.
Oh but Bear! you say. The spear-holder argument! Our ancient cavemen ancestors who had this palmaris longus tendon could better grip and throw their spears. Wouldn’t being a better hunter make them a more desirable mate for cavewomen?
No. No it wouldn’t. And let me tell you why.
The palmaris longus is a vestigial tendon, has been for eons, and hasn’t conferred an evolutionary advantage on those who have it since we lived in trees.
Yeah. A well-developed (aka, not vestigial) palmaris longus tendon is really only found in arboreal animals, like monkeys. Found there, it does give an advantage by augmenting grip strength, and thus making those tree-dwelling monkeys a little less likely to fall out of the tree. But among humans, who are terrestrial apes? The palmaris longus is not needed and is nothing but a relic. It’s been a relic since, like, Australopithecus.
Studies show that there is no difference in grip strength between those who have the palmaris longus and those who do not. Which should surprise no one because, again, the tendon is vestigial.
Now, to make up for me crushing your hopes of being a better spear-holder, let me share with you some great facts about the palmaris longus tendon!
It’s found in roughly a quarter of the population.
It has a ridiculous amount of variety in how it presents. In some people, it’s just a tendon running from A to B along the forearm with no associated muscle. In others, the muscle (which is also poorly-developed and vestigial) is found in the middle of the tendon. In others, the muscle is at one end of the tendon. Also, in some people, it’s only present in one arm and not the other–so if you see it in one wrist, check if it’s on the other side as well. I have it on both arms.
Because it’s vestigial and is not “needed”, it is the number one choice for use in reconstructive work. Surgeons will use it to repair or replace tendons just about anywhere in the body, because they can remove it without any ill effect!
This has been your daily dose of science. Bear, out.
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