I think having a «caller» was actually in the old D&D rules. AD&D 1st ed. Players Handbook p. 105 in the «Obedience» (hah!) section. Mentzer's Basic D&D (Red Box) has a section called «Mapper and Caller» on page 53 of the Players Manual.
.-= Alex Schröder´s last blog ..Gleichberechtigung =-.

It's a very old concept and I'm not sure if people still do that now. We use to elect the paladin in AD&D as the party leader because of their godly stats (back then, we still rolled for ability score).

Nowadays, we still choose a party 'talker' but he isn't always the party leader (if we have any at all).

As a GM, I've started using it as a device to move the plot forward when the party is undecided. Nobody wants to talk? Nobody knows where to go? Then I pick whoever I feel looks like an authority figure in character (which often isn't one of the more assertive players), and ask them: «So, what are you orders? Which direction are you pointing in? What do you say?»

It still works!

It was good advice back then, it still is now.
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People used to have much larger groups. I remember playing in a game at the Library in '85 and there were at least 10 players in the group.

With that many people the idea was that it's easier/faster for the DM if someone (the caller) can collect all the players actions (while the DM does DM stuff I guess) and then tells the DM what everyone is doing at the same time.
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In my games the "party leader" has always cropped up organically. I have a couple players who are just more outgoing than the others, and they do a good job managing the party, even to the point of encouraging newbie players to take the leadership position at times; for example, I ran an adventure where all but one PC was killed, the one survivor being the character of one of our less experience players. When the other players introduced new characters the next session, instead retaking the leadership position they encouraged the survivor's player to lead the group.
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The "caller" idea is a VERY old idea, and not one I would recommend for any gaming group. I think the idea may have originated for very young players, so that there was not a shouting match to get the GM's attention, but any gaming group with a modicum of civility should never run into this issue.

If a group DID have a problem with people talking over each other, a better solution would be to roll up initiative at the beginning of every session. Whenever more than one person wanted to react to the GM at a time, the GM could have each one react in their initiative order, going around the group.

Often groups do develop a party leader, but this tends to be more in-game than this metagame suggestion. I honestly hope that no gaming groups fall into this method of gaming.

I know i'm a few months late commenting but whatever. Anytime our group has a situation where multiple characters want to do something we roll initiative. This often crops up when meet new npcs. Our fighter will want to intimidate or scare them if not outright attack and our rouge will want to talk and try to use diplomacy. In the case of you are sitting around the fire and see eyes in the distance we'll do a spot or perception check and whoever sees them will be asked what they want to do.