Our conceptualization of reality is too rigid.
Which came first, the chicken or the egg?
Asking me that question is the quickest way to get me to ninja-chop all over your face. It's a dumb question. Well, no... it's not a dumb question. It's a bad question... and yes, there is a difference. I'll explain.
This question is a "problem" to ponder about a supposed infinite regress, but the core of the problem of the question itself, and what derails our ability to find a solution to it, is...
What is a chicken?
The species, Gallus gallus domesticus, includes a set of organisms with a variation of DNA, and we've decided, as humans, to label this set "chicken".
Let's say we start with a chicken. It lays an egg. The resulting chicken (we'll label it Generation 2), is 99.9999% genetically similar to its parent. Would we still call it a chicken? Sure.
Let's skip ahead 100 generations, where Descendant Generation 102 is 99.998% similar to the Generation 1 chicken. Would we still call it a chicken? Probably.
At what point do we stop calling it a chicken? When the new generation is only 95% similar to Generation 1? How about 80%. Well, we are something like 98% genetically similar to chimpanzees, so probably far before that.
The point is, we don't have to definite cutoff point. Common definitions of "species" tend to be when two parts of a greater common ancestor group can no longer reproduce, but even that is fuzzy. Our attempts to categorize "chicken" has limited usefulness.
Going back to the "Which came first, the chicken or the egg?", you should be able to identify the problem with the question. It's assuming that the lineage is static throughout time. Instead, if we look back 100,000 generations, we might not identify the predecessor as a chicken. It's not as though another species laid an egg that was suddenly a chicken - it's a slow gradient, so there's no exact point in which we could identify a cutoff point to establish whether the egg or the "chicken" was first.
Humanity's attempts to categorize species and taxonomy are like attempting to impose borders on the surface of the planet, and call them "countries" and "states/provinces". We may use a river to establish a border between States, but that river will slowly morph and shift, and erosion and sediment buildup reshape it.
Nature is going to do its thing, and it doesn't care how we try to organize it into nice little categories.
This is where it becomes difficult to explain evolution to others.
Brains are all about categorizing and detecting patters, so it's not a personal failing that we'll do it even when it doesn't make sense to do so.
All these creatures that we collectively call "chickens", unless they're clones, all have unique DNA, and that DNA doesn't necessarily have any boundaries as to how much it can change. Just like the surface of the planet doesn't care that we draw "borders" on it, neither does the genetics of these creatures.
Most creationists, it seems, don't understand the idea that a large amount of incremental small changes can result in wildly different species. "Show me a dog that gave birth to a cat", they request.
The problem is our imposition of our categories on life. That's what's confusing us.
We're used to thinking about organisms as pre-defined "slots" or "kinds". An organism within its "slot" may be able to vary mildly, but it'll always be a "chicken". Life isn't an ice-cube tray, where water fills in little cups, and it takes a lot of effort to move water from one to the next.
It's more like there's a water spill on the floor, and it's flowing/collecting in a scattering of different directions. Your attempts to categorize the regions of the water spill with a marker (because that's what you do with water spills, right?) only really work for short periods of time before you have to redraw what you once thought were the distinct boundaries between the regions, or not.
The primary reason why it's difficult to comprehend the lineage between a small rodent creature 65 million years ago, and modern day humans, is because one isn't familiar with each incremental step. We mentally start with one category - mice-like creatures - and another - humans - and our minds shuffle those concepts into self-contained non-overlapping mental boxes. It's difficult for us to understand the flowing changes over vast numbers of generations.
What's a better way of going about it? I'm not sure... at least, I'm not sure of any ways that doesn't have the creationist's eyes glazing over in under 10 seconds... sort of like me when they start spouting off Bible quotes at me.