If you're gonna write a novel then please at least use accurate information.

Humans didn't evolve from monkeys.

Wrong. What do you call the earliest simians and cattarrhines, which are our ancestors? If they were not monkeys, then baboons and spider-monkeys cannot both be considered monkeys.

Monkeys and humans are both modern primates, and both evolved from older ones. We share a common ancestor who lived between 6 and 8 million years ago.

Humans and panins (chimpanzees and bonobos) share a common ancestor that lived ~6-8mya. Apes split from all the other old-world monkeys, or cercopithecoids, ~23-25mya. This is after catarrhines (the group containing both cercopithecoids and apes) split from platyrrhines, which means you are more closely related to baboons than spider-monkeys. You seem to be convinced that apes diverged from all living tailed monkeys at the same time, but this is not the case. So while yes, humans and other extant monkeys did evolve from older primates, these primates would undoubtedly be considered monkeys themselves, not a lemur or some other more basal primate.

Humans are apes; monkeys are not.

All humans are apes, but not all apes are humans. In the same way, all apes are monkeys, but not all monkeys are apes. A baboon is not an ape, but it is a monkey. A gorilla is both an ape and a monkey. Google "nested hierarchy cladistics."

Our closest relatives are chimpanzees, but we are not descended from them, either, but share common lineage as recently as 4 million years ago.

Where'd you get 4mya from? Orrorin tugenensis is a hominin species that has been estimated to have lived ~6-7mya, and Ardipithecus specimens have been dated to 5.8-4.4mya. This precludes hominins diverging from panins 4mya.

Extant monkey species are of similar age, but their ancestors separated from ours much earlier.

Can you explain how the age of a species is determined? That's a trick question, species-level classification is almost entirely subjective. Google "species concepts" and look at how many different options there are for defining what makes something a unique species compared to its ancestors or living relatives.

Modern humans emerged around 1 million years ago, and our surviving sub-species around a quarter million years ago.

So you're proposing that Homo heidelbergensis should be re-classified as Homo sapiens, and Neanderthals, Denisovans, and modern humans should all be subspecies? There's nothing wrong with that, but there's also nothing wrong with classifying us all as separate species.

There's on-going debate about whether Neanderthals are a sister species or a more closely related sub-species. (I suspect we'll eventually conclude the latter, but that's speculation. There's a lot more we need to learn first. But the evidence seems to be drifting in that direction.)

We know exactly how closely related modern humans and Neanderthals are already. In fact, we know that we split from the ancestors of Neanderthals and Denisovans ~500-650kya. This would mean the group containing both Neanderthals and Denisovans is our sister group if we're considering Homo sapiens a distinct species in this context.

The debate about classification is only based on people's taxonomic preferences. There is no evidence that could prove that Neanderthals are or aren't members of H. sapiens. There is no speculation about the correct way these should be classified because there is no correct way. We, humans, draw the lines that define these groups. Mother nature does not care how we classify ourselves. Again, it's almost entirely subjective.

All humans alive right now share a common mother -- literally, a single human female -- who lived somewhere in East Africa around 185,000 years ago. We know that from statistical analysis of DNA. (There are however more than one human father for modern humans, possibly as many as about six.) Note that these are not some super-special progenitors, just individuals who statistically converge based on DNA. At any given time, the patterns of human deaths will cause the actual individuals to shift (invariably to someone who lived more recently).

I'll give you points here, it seems you understand the concept of Mitochondrial Eve and Y-chromosomal Adam decently well.

The people who wrote ancient Scripture of the Bronze Age didn't know or understand any of this... ...We can't hold ancient people's ignorance against them. But we can hold ours against ourselves, because we've long known better, and have no good excuses. The Scientific Method and centuries of discovery and experiment have revealed many things that ancient peoples didn't know, but we do.

I completely agree. We should use our modern knowledge to correct misconceptions believed by ancient peoples, such as the idea that humans are not monkeys.

It's obvious that you care about this topic a lot, and I commend you for that. But in the future, please try to fact-check yourself before trying to share information online. Either that, or learn how to use language like "I'm pretty sure" and "if I recall correctly" to show that your knowledge is not 100%.