When Jesus said, “This Gospel must be preached in the whole world as a testimony to all peoples,”...
...what did He mean by "all peoples?"
Note that there is only one major "people" within the borders of the country to the left (see Col. A). But this people of 12 million has three major geographic spheres (Col. B) within which (Col. C) there are seven major (mutually unintelligible) dialects. Within each dialect area there are perhaps 20-30 "confederations of tribes," Col D. And, in the final column E you see what may be 70 to 90 tribal groups (which may or may not be friendly to each other but which) certainly consider themselves separate.
So how many "peoples" are there in this country? You'll note we are having to guess at how many groups at the lower levels. In any case the total number depends on which level you count.
For example, Wycliffe Bible Translators will probably find that they can get by with printed (eye gate) Bible translation on the level of the three major spheres, or at the worst, at the level of the seven dialects. For Wycliffe there may be no more than three or seven "peoples" to deal with.
But Gospel Recordings (people who deal with the much more discriminating ear gate) inevitably needs to deal with the next level of 20 to 30 groups, and just perhaps even in some cases with the tribal level in case the language differences when spoken out loud at that lowest level are sufficiently different or even if they are merely offensive!
Remember, both printed and audio media are valuable, but the relevant number of groups is different in each case. To make things more complicated, note that sizable groups of this overall people are in nine other countries, as well! And, these other groups come from any one of these different levels you see here.
But, now, at what level was Jesus speaking? He wants, of course, to reach through to all groups, behind whatever barrier of understanding or acceptance there may be. The answer is simply that we'll find out the answer the closer we get to the situation. In the meantime we need to live with guesses.
This is why it is literally possible to say--depending on whether we are referring to levels A, B, C, D or E--that there are only 250 or so major peoples in the whole world, or 900 or so major language families, or 4,000 significant peoples (of which 1,700 are in great spiritual need) or 10,000 or 20,000 still smaller peoples. It all depends on which level you are concerned.
Right now, the list of 1,700 needy peoples listed in this issue (pp. 17-23) is a concrete and valuable target. We can only learn more as we go!
AND, at this hour greater human resources are looming into view than have ever been available to the unfinished task! Are you part of it?