Evolution and irreducible complexity
A mutation is random, but given enough time, these random changes in our DNA regularly contribute something positive. Thats how we evolve, as simple as that.
- Mutations and organ development
- Irreducible complexity & Circular dependency
- The Circulatory System
- The Digestive System
- Mousetrap (the classic Irreducible complexity example)
- Chicken or egg
Mutations and organ development
The most basic mutation is a point mutation, this is when a single base pair in our DNA is altered. A point mutation can be a deletion, a duplication, an inversion, an instertion, or a translocation. An alteration in DNA causes a change in a certain trait of the organism.
How did, for example, the human heart evolve? The heart is a fairly simple organ conceptually, it's a muscle that pumps blood through the arteries. Evolution wise there were two posible pathways: 1) The heart evolved from version one, to version two, to version three... up until the version we have now. Or 2) The heart was one of many lucky accidents, and version one was immediately perfectly functional, and in the right place, and attached to the right stuff, etc.
Evolution is supposed to work in a stepwise fashion over long periods of time, right?
Despite of the need for thousands simultaneously occuring perfect point mutations, pathway #2 ís the more sensical one. This because, with #1, if the first heart had need for further development, to accidentally gain a purpose, than that means that this first version of the heart was useless or ineffective, and that's a problem. A big hunk of muscle that looks like it should pump blood, but doesn't pump blood, and actually does nothing, is useless. A useless organ is practically nothing more or less than a benign tumor.
There is no such thing as a good tumor. Even benign ones may cause pain and disfigurements. It doesn't contribute to the organisms survivabilty. More likely are the chances that it'll burden its survivabilty or its sexual attractiveness. So a useless organ isn't only useless, it is also harmful.
DNA of useless organs, or tumors, are less likely to get passed on to next generations because of these fitness flaws. This prevents the prototype organ to evolve into its next version.
So the very first heart had to be fully perfect, functional and operational. How many simultaneous perfect point mutations would that have required?
Irreducible complexity & Circular dependency
The bit about the heart is only there to point out that organs on their own are already way to complex to happen without devine guidance. And I could leave it at that, but its only a small part of a bigger point.
Organs never operate independently of other organs, and that makes things immensely more complex, and thus even less likely to just happen.
A big hunk of muscle that should pump blood, but doesn't, is useless. On top of that, a perfectly funtional organ in less than perfect circumstances is just as useless:
The Circulatory System
- A heart without veins and arteries, is useless
- A heart without blood, is useless
- Veins and arteries, without a heart, are useless
- Veins and arteries, without blood, are useless
- Blood without a heart, is useless
- Blood without veins and arteries, is useless
Systems like these have an Irreducible complexity. The heart, veins and arteries, and blood all have a dependancy on all others to a point where if one fails or is missing, the organism dies. The term Circular Dependency comes to mind too, it comes from Software Engineering, but beautifully fits here too. Here some more examples:
The Digestive System
- A digestive system without teeth, is useless
- A digestive system without a throat, is useless
- A digestive system without a stomach, is useless
- A digestive system without bowels, is useless
- A digestive system without an anus, is useless
Complete dependency breakdown
- A mouth without teeth, is useless
- A mouth without a throat, is useless
- A mouth without a stomach, is useless
- A mouth without bowels, is useless
- A mouth without an anus, is useless (yes, I realize I wrote that)
- Teeth without a mouth, are useless
- Teeth without a throat, are useless
- Teeth without a stomach, are useless
- Teeth without an anus, are useless
- A throat without a mouth, is useless
- A throat without teeth, is useless
- A throat without a stomach, is useless
- A throat without an anus, is useless
- An anus without a mouth, is useless
- An anus without teeth, is useless
- An anus without a throat, is useless
- An anus without a stomach, is useless
Any failiure in any of these parts makes the whole Digestive System useless. The full dependency breakdown initially felt a bit to much to include in this article, but all of these dependencies illustrate differently how even a prototype digestive system would need all of these parts. Even single cell organisms have an input organ, an output organ, and everything in between. Organisms who would have recieved these organs one by one, over multiple generations, would not have survived long enough to reproduce. And it doesn't matter which organ evolved first.
Oh you'd argue that some of these statements aren't true because some organs have multiple functions? Now, how does that make things less complex, and more likely to develop through evolution?
Side note on multifunctionality, we actually talk with our digestive system... the very first language ever must have been a set of diverse burps. And I bet the first response to the first thing ever said was laughter.
- A clock without hands, is useless
- A clock without a dial face, is useless
- A clock without mechanical parts, is useless
Mousetrap (the classic Irreducible complexity example)
- A mousetrap without a base board, is useless
- A mousetrap without bait, is useless
- A mousetrap without a spring hammer, is useless
- A mousetrap without a catch, is useless
- A mousetrap without a holding bar, is useless
Well, a spring is a pretty handy object on its own and you might be able to use it in an other way. - some blogger
Yeah, you'd be totally alive if your perfectly functioning heart, separated from any veins, evolved on your elbow. No, a spring is useless as soon as it falls out of its intended place. Try it your self: disassemble a pen and build something new and usefull with the spring. It is hard, and it will require thinking, and designing.
Chicken or egg
A classic somewhat related question: What came first, the chicken or the egg? Easy answer though: the egg. Scientists have found that there were eggs thousands of years before the chicken evolved. First there was the egg, and turtles, snakes, crocodiles, and birds all crawled out of it. So... where did the egg come from again?