Well, I imagine you're not particularly happy with being contradicted. My apologies.
It's a relevant point, however, since people keep mentioning the Hist as though the Argonians are either related to them, or genetically manipulated/created by them. Consider this entry from the UESP Wiki:
The Hist have been tossed around quite frequently on The Elder Scrolls Official Forums, all due to one dangerously mislaid sentence. In the PGE, Argonians are said to never have left their homeland "except for a relatively intelligent strain called the hist.[sic]"[1] This statement, implying that the Argonians are a type of Hist, left quite a bit of fallout, but was resolved by a clear statement by Mark Nelson that the whole thing resulted from ignorance on the part of the editors of the Guide. Hist are, in fact, great sentient trees worshiping the eternal, immutable, god of chaos, Sithis.
This seems to indicate that the Argonians probably weren't "created" or "engineered" by the Hist, nor are they a species of Hist.
A further excerpt:
Argonians are known to have deep connections with the Hist, calling themselves "people of the root,"[5] and licking the leaking sap of their trunks in religious rites.
"Deep connections" ≠ shared common ancestry or creation of the Argonians by the Hist. Assuming anything else is exactly that, assumption.
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So in conclusion, it can be argued that Argonians and dragons do, in fact, share a common ancestry, or "kinship" if you will. Both species have scales, they have claws and spines, they have tails, they reproduce by laying eggs, and in many respects they look very similar. It would be a stretch to argue that they
aren't related, given all the similarities. In this case, the real question is how far back in the history of Nirn the two races started to diverge.
Of course, given that this assumes an evolutionary viewpoint and that Nirn is a fictional, magical world with a pantheon of divine beings, it's impossible to say for sure.
So, as you see, it is doubtful that Argonians evolved from dragons, being dragons still largely exist
There are thousands of species living in the real world whose ancestors are still alive today.
It's called divergent evolution: If part of a species migrates to another area of the globe (or some other, similar change), the displaced species may evolve significantly while the original species remains largely unchanged.