Some of the most common words in Japanese seem to have their origin in Chinese:
The evidence for this is, as far as I know, the fact that these words are written with characters, whose on-yomi is used to read that particular word.
Further evidence is that there usually is a synonym or an archaic form, that is written using characters whose kun-yomi is used:
会議 ＝ 出会い 日本 ＝ 八洲 （やしま）according to tangorin.com
I imagine that these words were used by the Japanese before the introduction of Chinese characters to Japan.
However, some words do not have this form:
世界 ＝ ？ 先生 ＝ ？
How did the Japanese folks say these things before the introduction of Kanji and what happened to these words?