Junk DNA and Vestigial Organs

This weeks episode of That’s a Fact is called Useless Body Parts:

Oh yes, and we’re back to embedding not working again. Give it a few days… [Edit: What did I tell you?]

Ever had your tonsils out, or maybe your appendix? You’ve probably been told that these organs are vestigial, or unnecessary organs in the body, leftovers from evolution.  But scientists have discovered that these “unnecessary” organs are actually very useful. For instance, the appendix plays an important role in the immune system, which helps us fight off illness. The Gallbladder is another organ that was once considered useless, but we know it is needed to digest fats. Tonsils, wisdom teeth, the thymus gland, the tailbone, and the little toe – they were all thought useless at one time, but now they are seen as very important. A person can survive without these organs, but it’s best to leave them alone.

Vestigial organs are things in the body – not necessarily organs – that have lost their original function but which may still retain a minor function or have evolved a new minor function. This function, however, is not enough to prevent mutations pummeling the organ to the point where it more or less atrophys.

Consider a desalinisation plant, which has been disused. The plant is still there, and one or two pipes and a pump may still be used as part of the mains water system, but most of the pipes run in random directions and the building blows up from time to time. If you were going to design the little pumping station that the plant has become from scratch what you have know is not what you would build. Additionally, it’s not a case of having the plant already there waiting to be modified, but you build the plant in full (though not in complete working condition) each time and then only actually use part of it. Sure, it has a ‘vital function’, but it doesn’t justify the plant’s existence.

A good example of a vestigial organ are the eyes of moles. Moles spend much of their time in the dark, and don’t really need to see all that much. consequentially, their eyes appear “stunted in developement.” One type of mole, the blind mole rat, spends even more time in the dark and it’s eyes are covered in a layer of skin – they are completely useless. While it could be possible that there is some use to having the eyes there, there is unlikely to be reason for complete eyes to be made and then covered with skin, rather than a simpler system. Evolution dictates that existing structures may be reused for a new purpose, but a system of design is not limited in this way. So why are they there?

Another illustrative example in humans is the developement of the kidneys. First one pair developes…and then dissolves. And then another one..but then that vanishes too. Finally, a third pair turns up and sticks with us. Why does this happen? Because Haeckel had a point – developmental stages are conserved.

As for the examples given in the video:

• The vermiform appendix is the most famous of all the vestigial organs. It’s original function was to harbour bacteria that break down cellulose – in other animals it still does that. But the version in humans is incapable of performing that function. Any other function that the appendix might have is mostly speculative, and probably has something to do with harbouring other bacteria, for example to prevent them being flushed out by diarrhoea. If it does turn out to have a function, it can certainly be improved on as the whole appendicitis thing probably counterbalances the small gain that we might be able to get from tolerating its existence. Having a function would not make it not vestigial, however.
• The Gallbladder, on the other hand, it not vestigial – it retains its original role. However, like with the appendix, if it is removed you aren’t all that negatively affected.
• The same goes for tonsils.
• Wisdom teeth are vestigial, and a sizable portion of the population do not develop them while many others have them removed. I am not aware of any function that they may have.
• The thymus gland is a legitimate case of an organ formally considered to be vestigial, but which is in fact very important.
• The tailbone makes quite a good poster boy for vestigiality. It’s frankly blatant that it’s the stump of a tail, but the remaining bone does have a minor use – the anchoring of muscles and also in weight distribution. The point here is that repurposing a few fused vertebrae that otherwise would have been destined to simply disappear is how evolution would do this – a God would likely have done it differently.
• I would guess that the little toe is important for balance, but there were probably better ways to have done it.

The same goes for so-called “Junk DNA.” Researchers once thought that some of our molecular makeup was just scrap, that didn’t have any purpose. But recent studies have found particular components of junk DNA that are vital to life.

Junk DNA exists.

There is a Kiwi biologist who has started a blog series on this subject – this blog post, among others, is quite helpful when it comes to understanding the concept. To summarise:

• Introns, which divide genes into bits making it possible for them to arranged in different ways, are unnecessarily long. We’re talking orders of magnitude here.
• Transposable elements, sections of the genome that are capable of jumping around and copying themselves to new places, make up significantly more of the genome than anything we know to be useful in the form of mutated “corpses” in various states of decay.
• It was predicted, back before the genome was sequenced, that we could have no more than 30,000 genes due to the difficulty of repairing mutations. At the time we were thought to have 100,000 genes – the tally presently stands at 21,000.
• It doesn’t seem to matter if a mutation strikes any part of the genome except for a very small portion, most of which we know what it does – if the rest isn’t junk, its function cannot rely that much on its sequence.
• It is true that “studies have found particular components of junk DNA that are vital to life,” but on the scale of the genome we’re still talking 90%+ being useless and in most cases the discoveries are miniscule – while more useful section are being found, it’s not looking likely that we will ever find a use for it all. There will always be more crumbs on the plate, but it will never substitute for a good dinner.

The creationists keep saying that Junk DNA does not exist, despite all the evidence. They often say that the parts of the genome that aren’t genes are all ‘regulatory DNA’, but remember when they do so that they are saying that 96% of the genome is ‘regulating’ the 4% that is genes.

God doesn’t create junk, and when he made Adam and Eve he declared them very good. Their sin against God started the process of sickness, decay, and death, but even after God’s judgement upon creation he activated intracity designed back-up systems, like the immune system, so that Adam and Eve and all their descendants could survive after the fall. God created every human with absolute perfection, even designing organs and body systems that allow us to survive on Earth. And, through the gift of salvation, access to heaven through Jesus Christ.

That should give you the reason why the creationists must argue against useless things at every turn. Interestingly, the ‘intelligent design proponents’, another breed of creationist, seem to be able to accept that their Designer – who Must Not Be Named, least the whole facade of secularism in their movement crumble – does not seem to make things perfectly. But at the same time, despite not being wedded to the theo-logic in the above paragraph, they can’t accept the existence of Junk DNA – these are the people who wrote The Myth of Junk DNA, a review of which begins here.

So, vestigial organs and Junk DNA exist, and the creationists aren’t happy and want to pretend that they don’t. What’s new?