Moreover, your attempt to apply modern anthropology here is utterly untenable.

From the rising of the Sun (and the awakening of the Second-born) to the end of the War of Wrath (when the Elf-friends of the Edain were rewarded) was less than 600 years!

Men can only be physically diverse if they were created that way.

Ditto for hobbits and dorfs, who can't have been around much longer.

Elfs have had more time, but with their low fertility, there can't have been many more generations than the shorter-lived mortal races.