The human body as proof for evolution

The human body has several organs that don't make sense. The two most obvious are the appendix and the sacral bone. The appendix, as you may or may not know, is a "pocket" at the end of your large intestine. Stuff acummulates in it. If you're lucky, you never know it's there. If you're unlucky, doctors have to take it out, because it becomes inflamed. If you're very unlucky, it explodes, and you die. (Seriously, my dad's appendix burst. He almost died.) So what is it good for? In cows, it help with digestion. In humans, it is mostly good for interns who need to practice simple operations. It has no useful function. It is proof humans evolved from cows. (kidding).

The sacrum, or tail bone, is just what it is. It's what really hurts what you bang the top of your bum. It serves no purpose, other than looking funny on X-rays. Unless you are a devout non-believer in evolution, you'll agree it's a remnant of a tail. Proof humans evolved from lemurs. (kidding again).

And now to my personal favourite: the palmaris longus muscle. This is a muscle in your forearm. Actually, it's a muscle that 90% of people have in both forearms. It's a flexor muscle for the hand. It lies just under the flexor carpi radialis. Bunch your hand up into a fist. Now flex your hand (this means that, palm up, bring your hand towards you). How many tendons do you see? If you see just one, that's the flexor carpi radialis. If you see two, that's the fcr and the palmaris longus. We don't need it. It's a weak muscle that is not useful. Less and less people have it every generation. Like I said, 10% of the population have it missing in one or both arms.

There is also a similar muscle in the leg. And the foot has too many muscles for its function. The foot has about as many muscles as the hand. See what you can do with your hand, compared to what you can do with your foot. It doesn't make sense. Unless we developed from creatures who use their feet much like they use their hands. Proof humans evolved from koala bears. (I'm kidding, enough already).

We don't need to look very far for proof for evolution. It's right here.

Azure Monk:
You are right, of course. Then again, evidence might even be too strong a word. I chose the word "proof" because it goes well with my bad jokes in the middle.

As a biologist, I feel compelled to point out that two of the organs offered as vestigial are not actually recognized as such today.

Sacrum

The sacrum serves at least two vital functions. First, the sacral nerves need to exit the spine below the juncture of spine and pelvis to innervate the buttocks, legs, and other *ahem* important *ahem* organs. Without the sacrum descending below the rest of the spine as protection, these nerves would be much more prone to damage and paraplegia would be correspondingly more common.

Further, the structure of the perineum necessitates an attachment point for muscles which might be regarded as "important" (defecation would be either impossible or "automatic" depending on which muscles were detached) and *ahem* important *ahem*. The coccyx, which articulates with the distal end of the sacrum, provides these anchorage points.

Appendix

The appendix serves at least two known important purposes. First, it is one of the densest patches of immune tissue in the human gut. Gut-associated lymphoid tissue (GALT) is one of the first lines of defense in the body, as the gut is the system most exposed to the outside world (What? You thought it was the skin? Nope. Skin cells are protected from direct contact by a thick armour plating of dead, keratinized cells.) and thus most often exposed to pathogens. GALT both produces and stores the immune cells which respond to potential pathogens.

The pocket-like "dead end" structure of the appendix allows it to capture small amounts of matter as digestion proceeds and "examine" it for longer than most other GALTs. As generation of "matching" immune cells is a probabilistic process (immune cells are generated at random and ones that find a "matching" pathogen proliferate), this "lag time" assists in the detection of and defense against pathogens.

As well, the fact that the contents of the appendix are only slowly "turned over" and replaced makes it a haven for essential gut flora ("good germs") in case of catastrophic (from the gut's perspective) events such as diarrhea which flush most of the flora from the gut.

For these reasons, people with intact appendices both suffer a lower incidence of gastrointestinal infection and recover from such infections much more quickly.

While no studies that I've been able to find — granted, in only about fifteen minutes of searching the literature — seem to deal with the consequences of a missing palmaris longus muscle, it may contribute (like other weak muscles which work alongside stronger muscles) to stability rather than to strength. I'll leave that for those who could actually research it, though.

If you still think the sacrum is vestigial, though, I'll remove yours for you.