The phrase "ancient assumptions" is correct and usable in written English.
It can be used when discussing beliefs or ideas that have been held for a long time, often without questioning their validity.
Example: "The study aimed to challenge ancient assumptions about the nature of human behavior."
Alternatives: "long-held beliefs" or "timeworn notions".
We're having to reverse deep and ancient assumptions about how we allocate goods, labor, money, and power on a rapidly shrinking, endangered, complex, and ever more populated planet.
Two centuries ago William Wilberforce, a lifelong social activist, goaded churches in England to rethink the ancient assumptions that allowed people who saw themselves as virtuous and religious to accept slavery as "normal".
If we allow ourselves the power of an independent imagination -- thought-forms that don't flow in a perfunctory manner from ancient assumptions merely handed down to us, but rather flower into new archetypal images of a humanity just getting started at 45 or 50.
This hypothesis was an important step in disproving the ancient assumption that atoms were indivisible.
Defending pap photos of Hutchence in a bikini as in the "public interest" is the defence of an ancient patriarchal assumption that female bodies are social property.
The best available science today (including evolutionary theory and psychology) supports rather than undermines the ancient Greek assumption that we are social animals, like elephants and wolves and unlike polar bears.
In the case of most ancient authors, the assumption is that a text handed down in their name is genuine, unless strong reasons can be given for regarding it as a forgery.
So the translation 'name' is not inept nor is the ancient Chinese theory assumption that all words name the part of reality which the word "picks out"—roughly "naming" what we think of as its denotation or scope.
In the torso section there are two unique figures that make viewers revisit their assumptions about ancient Egyptian art's focus on the idealized form.
Our assumptions about ancient cultures are all too often guided by modern beliefs about the universality of gender roles at different stages of cultural development.
The equant, however, broke with the main assumption of ancient astronomy because it separated the condition of uniform motion from that of constant distance from the centre.
