All language (change) over a period of time? English tense problems Why not use the simple present tense?

All language (change) over a period of time? English tense problems Why not use the simple present tense?

All languages have changed over a period of time
The reason has been put forward
Because the general present tense is just to express what happens at this moment, but language or many things are imperceptibly changed in a long time, so it means from a period of time before - now, so we should use the perfect tense