Irreducible complexity is a undeniable fact
The argument of irreducible complexity is obvious and clear. Subparts like a piston in a car engine are only designed, when there is a goal where they will be mounted with specific fitting sizes and correct materials, and have a specific function in the machine as a whole. Individually they have no function. Same in biological systems, which work like factories ( cells ) or machines ( cells host a big number of the most various molecular machines and factory-like production lines ) For example, in photosynthesis, there is no function for chlorophyll individually, only when inserted in the light harvesting complex, to catch photons, and direct them to the reaction center in Photosystem one and two. Foreplanning is absolutely essential. This is a simple fact, which makes the concept of Irreducible complexity obvious concept. Nonetheless people argue all the time that it's a debunked argument. Why ?
Soren Lovtrup, professional biologist in Sweden, said
"...the reasons for rejecting Darwin's proposal were many, but first of all that many innovations cannot possibly come into existence through accumulation of many small steps, and even if they can, natural selection cannot accomplish it, because incipient and intermediate stages are not advantageous."
Irreducible complexity keeps being a unsurmountable problem for the ones that propose unguided evolution and natural mechanisms to explain the origin of life and biodiversity in general. No attempt to refute and successfully debunk the argument has been brought forward so far. Every attempt, no exception, has failed. Why ? Because IC is an undeniable FACT, no matter what. And this FACT becomes obvious to the unbiased mind when we envision biological systems as complex molecular machines, that operate similarly to man-made machines, but far far more complex. Individual parts have no function by themselves. This is an important point to highlight.
What use does the wing of an airplane have alone? None. The engineer has to envision a function for the wing, used as essential part of the design of the airplane as a whole in order to fly, and its use once the airplane is fully built with all parts in place. The wing must be made with the right specifications, size, materials, form, and placed and mounted at the right place in the right way. And the wing itself requires complex machines to be made. The right materials must be transported to the building site. Often these materials in their raw form are unusable. Other complex machines come into play to transform the raw materials into usable form. All this requires specific information. The precise same thing happens in biological systems. Even the most simple cell uses numerous parts, that have no use by their own. For what reason would natural mechanisms create these parts, if there were no use for them individually?
This is a problem that stretches through all biology, from the simplest to the most complex. Biological systems do only achieve specific tasks, once a number of individual parts are made upon specific complex instructions, frequently through other specific machines or even factories and assembly lines, that have no other tasks than to build these specific parts, and all this through the instructions of the blueprint in the genome, and then other specific instructions provide the information of how, when, and where to mount the parts to form the complex machine. Same as done when building human-made machines. And all these processes must be strictly controlled, with error check and feedback mechanisms, and if something is not built to the right specification, complex repair machines fix the problem. These checking and repair systems must be fully operational from day one, otherwise, the organism dies. And the energy in usable form must also be provided , and the making of energy requires also complex machinery which by itself requires energy to be made ( chicken-egg problem ).
Furthermore, internal and external communication networks must be established. Also, all these machines are made to self-replicate, which adds a huge amount of further complexity into the picture. Self-replication is far from simple. It demands the most complex molecular machinery, which works in an astonishing, beautiful, orchestrated, regulated and controlled manner. Why at all would natural unguided, non-intelligent chemical reactions have the need to produce living biological systems, and keep them existing through self-replication?