I was previously curious how many countries declared themselves to be the heirs of the Roman empire, and I found there is something of a wikipedia list: https://en.wikipedia.org/wiki/Third_Rome
The comparison between China and Turkey as descendants of the Roman Empire is a bit of a stretch. China at least uses the same language (old Chinese poems written in the Tang dynasty and even Han dynasty can still rhyme correctly and make sense if read in Cantonese), holidays, culture, etc. Turkey doesn't use a romance language or Greek.
Japanese explicitly borrowed Chinese characters, it doesn't "share" them. It's just like modern English and Latin: English uses Latin characters, but it's not at all the same (or even a similar) language. Lots of languages use the Latin character set, and even Japanese is adopting more and more "Romaji". The characters a written language adopts has little to do with its relation with other languages from a linguistic point-of-view. Latin characters can be used for any language.
My guess is that civilization is too nebulous of a term for good discussion, but thats just my 2p.
the Chinese script have evolved, but one can still look at inscriptions from thousands of years ago and understand it.
it might be hard for people to understand different dialects in China but they all use the same writing system, standardized in the Qin dynasty.
Same with the borrowed Chinese characters in Japanese and Korean. A native Chinese speaker would have little problem reading those, although the pronounciations might be a little different
'ȝ' becomes 'g', 'Ð' becomes 'D', and we still use 'æ' today, which is also a rune, and they even used 'W'!
Also, the number of characters in Chinese has also drastically changed over time. So while many characters have a 1:1 lineage, far more characters simply did not exist 1 or 2 thousand years ago.
The only commonality is that they are based on pictographs and have a traceable etymology, although that's true for all languages.
The Japanese pronunciation of Chinese characters is absolutely nothing like the Chinese pronunciation of them, and the meaning is sometimes different too. (The Kanji for "letter" (as in a piece of paper you write a letter on) means "toilet paper" in Chinese.)
Are you Indiana Jones?
With some training, people can read seal script inscriptions because the structure is already fairly close to regular script which is what people use today.
The radicals are written in slightly different styles from today. It actually makes sense. Seal script is a very artistic form of calligraphy, so people use it for their seals hence the name.
An example of the "drum" character: http://www.guoxuedashi.com/zixing/yanbian/11208mb/ The horizontal arrow is the time line, starting from oracle bone script. The 4th one of the first row is seal script and the last regular script.
The idea depicted here is hitting a decorated drum on a rack with a drum stick holding in the hand.
https://en.wikipedia.org/wiki/Seal_script
If you look at the picture on the upper right, you can make out "tian xia" and "wang" -- all under heaven (i.e. the world) and king (the character for emperor isn't invented yet)
Hmm it's right there。 The 4th “皇” and 5th “帝”。 And the combined form “皇帝” - a title invented by the First Emperor himself。
For example: Japan shares many characters with Chinese, and Korean and Vietnamese both used to use Chinese characters, but they are all separate languages. Similarly, numerous "dialects" in China are less mutually intelligible than many different Western languages. Compare Portuguese and Spanish to Cantonese, Mandarin, Taiwanese (Hokkien), Fuzhounese, Shanghainese, etc. Not to mention languages like Mongolian (see the Yuan dynasty). And that doesn't even begin to get into even more ethnically diverse regions like Tibet and western China.
Then there's also the "warring states period" when, for over 250 years, no fewer than 14 different independently governed states made up what is today eastern China.
Claims that China has always been one civilization are politically expedient versions of history that glaze over an enormous quantity of inconvenient facts.
Did you know that after the Ottoman Empire conquered Constantinople, Sultan Mehmed viewed himself as the successor of the Roman Empire and declared himself "Caesar of Rome"?
China today is as much a continuation of those previous states as Turkey is of the Roman Empire.