Acts 2:1-11
And when the day of Pentecost was fully come, they were all with one accord in one place.
And suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the house where they were sitting. And there appeared unto them cloven tongues like as of fire, and it sat upon each of them. And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance. And there were dwelling at Jerusalem Jews, devout men, OUT OF EVERY NATION under heaven. Now when this was noised abroad, the multitude came together, and were confounded, because that every man heard them SPEAK IN HIS OWN LANGUAGE. And they were all amazed and marvelled, saying one to another, Behold, are not all these which speak Galilaeans? And how hear we EVERY MAN IN OUR OWN TONGUE, WHEREIN WE WERE BORN? Parthians, and Medes, and Elamites, and the dwellers in Mesopotamia, and in Judaea, and Cappadocia, in Pontus, and Asia, Phrygia, and Pamphylia, in Egypt, and in the parts of Libya about Cyrene, and strangers of Rome, Jews and proselytes, Cretes and Arabians, we do hear them speak in OUR TONGUES the wonderful works of God.
These are earthly languages. The Apostles needed to spread the gospel to all nation and did not have the time to sit down and learn languages before they set out for this undertaking. So what happened is that they spoke in their own language and the Spirit of God translated their utterances to the language of the foreigners that heard it.
1 Corinthians 14:21
In the law it is written, With men of OTHER TONGUES and other lips will I speak unto this people; and yet for all that will they not hear me, saith the Lord.
Again this is speaking of foreigners.
Revelation 7:9
After this I beheld, and, lo, a great multitude, which no man could number, of all nations, and kindreds, and people, and TONGUES, stood before the throne, and before the Lamb, clothed with white robes, and palms in their hands
This clearly demonstrates that tongues are human languages because nations, kindreds and people are human categories.
Genesis 10:20
These are the sons of Ham, after their families, after their TONGUES, in their countries, and in their nations.
Ham and his families spoke the language of their countries and nations.
The many tongues Paul boasted about were human.
1 Corinthians 14:18
thank my God, I speak with tongues more than ye all:
Now read the proof that he was a multi-linguist.
Acts 21:37-39
And as Paul was to be led into the castle, he said unto the chief captain, May I speak unto thee? Who said, CANST THOU SPEAK GREEK?
Art not thou that Egyptian, which before these days madest an uproar, and leddest out into the wilderness four thousand men that were murderers?
But Paul said, I am a man which am a Jew of Tarsus, a city in Cilicia, a citizen of no mean city: and, I beseech thee, suffer me to speak unto the people.
AND WHEN HE HAD GIVEN HIM LICENSE, Paul stood on the stairs, and beckoned with the hand unto the people. And when there was made a great silence, he spake unto them IN THE HEBREW TONUGE, saying, Men, brethren, and fathers, hear ye my defence which I make now unto you.
The many tongues Paul is speaking about are human languages. He spoke Hebrew and Greek. I'm guessing he spoke more, but these are intelligible human languages.
Much has been made of the unknown tongue, to me this is a matter of a langue that one does not know. Spanish is an unknown tongue to me because I don’t understand it, not because it is a divine language.
1 Corinthians 13:1
Though I speak with the tongues of men and of angels, and have not charity, I am become as sounding brass, or a tinkling cymbal.
Just because angels have a tongue does not mean that men speak it. This seems to be more hyperbole than doctrine. He is really driving home the point that it is not the spoken tongue that matters, but the comprehension of the hearer. Here is the death nail to the movement that tongues is gibberish.
1 Corinthians 14:21-22 In the law it is written, With men of other tongues and other lips will I speak unto this people; and yet for all that will they not hear me, saith the Lord. Wherefore tongues are for a sign, not to them that believe, but to them that believe not: but prophesying serveth not for them that believe not, but for them which believe.
If tongues are a sign for them that believe not, why would the unbeliever be amazed over utterances they can not understand? The amazing part is that they understand it while knowing the speaker is not of their nation. Notice the scripture says for all this they will not hear me. Sometimes not hearing is a matter of obedience and not understanding.
Isaiah 66:4 I also will choose their delusions, and will bring their fears upon them; because when I called, none did answer; when I spake, they DID NOT HEAR: but they did evil before mine eyes, AND CHOSE that in which I delighted not.