The phrase "ancient relationship" is correct and usable in written English.
It can be used to describe a connection or bond that has existed for a very long time, often in historical or cultural contexts.
Example: "The ancient relationship between the two civilizations is evident in their shared artifacts and traditions."
Alternatives: "long-standing connection" or "historical bond".
There is an ancient relationship between monarchy and art.
Some researchers believe that the alarming increase in autoimmune diseases in the West may owe to a disruption in the ancient relationship between our bodies and their "old friends" — the microbial symbionts with whom we coevolved.
And in those times the routes to salvation led, almost inevitably, to the warm, fertile lands that lay spread out across a vast archipelago south of China, where the Chinese emperors had established a centuries-old network of trading routes and an ancient relationship based on vassal and tributary states, with the ports of Singapore and Malacca at its epicenter.
While most biologists rely on genetic analyses to untangle relationships between organisms, the authors of this study believe that such structural similarity reveals an ancient relationship between the two viruses.
We are looking at an ancient relationship that's still functioning.
There is an ancient relationship between women and water, according to the Taste of Love festival website, which promises a "ceremonial session" with the space to "explore our female nature, and release the emotions stored in the vagina".
Most linguists dispute that classification, saying languages change too fast to allow any very ancient relationships to be discerned.
For Japanese IT departments, deciding about hardware comes first, with each bank tied through ancient relationships to a single manufacturer: DKB to Fujitsu, IBJ to Hitachi, and so on.
The novel aspect of their analysis is that they focused on the parts of the rRNA molecule that mutate very slowly and so are likely to reveal ancient relationships.
As heterotrophic organisms fungi are often involved in symbiotic relationships, and fossil evidence for such ancient relationships exists [48].
It should be emphasized however, that the ancient relationships among expansin families are difficult to resolve.
