This is not irreducible complexity at all.
As defined by Michael Behe, the man who coined the term:
Irreducible complexity is just a fancy phrase I use to mean a single system which is composed of several interacting parts, and where the removal of any one of the parts causes the system to cease functioning.
I appreciate the quote, my only information about ID coming from the links and information posted in this thread.
I can’t say there is much that I would consider to be irreducibly complex, since the overall complexity of living forms can take many shapes and sizes, while remaining true to what it is. Maybe the context of the quote, which I am too lazy to pursue, might clarify what he meant.
I would use the term in a different sense, meaning that the complexity of a living system is not reducible to its constituent parts. The level of order of the overall system is its soul, which utilizes the material components of which it is constructed, to express the kind of being it is. Let’s take ourselves for example; my way of using such a term would be to indicate that as a person, we can lose pretty much everything that we are physically and psychologically, and still remain human. In terms of the subject at hand, stem cells, considering the fertilized human egg as the ultimate example, it exists as a person at the point of its conception.
With regards to evolution, if it becomes clearer that diverse species originated from a pluripotential organism, the really difficult, if not impossible question the theory of evolution has to address is how that organism came to be.
The ultimate Source is God, who brought life forth in steps, utilizing what had been earlier created as the physical universe: light, then atoms, then cells, then multicellular organisms, and finally beings with eternal souls, capable of knowing their Maker, capable of love.
I don’t think that God being God, did this through common ancestry. There is no need for this. Even what I would consider a remote possibility were how different kinds of life came to be, the fact is that with each step up the hierarchy of being, from atoms to we ourselves, a new set of relational capacities, types of souls, if you will, had to be created. And, the physical aspect of these successively more complex creatures, could not have simply morphed in accordance with the random activity of events following the fundamental laws of physics and chemistry. Additionally, survival is the shadow of what actually we see in nature, where everything has its place, depending on and transforming the common environment that includes all organisms.