Noah's people were the only humans on earth at that time
19-12-2013 | IslamWeb
Question:
As-salaam alaikum. I have read some of your fatwa which state that the flood during Prophet Noah's time was global. If that was the case, then was Noah (pbuh) also sent to all the people of the earth or just to his own people? The Quran states that Allah (swt) never destroys people until He has sent a warner to them. If Noah (pbuh) was sent only to his own people, how could the flood have been global? Jazak Allah Khair.
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
During the time of Nooh (Noah) 
there were no human beings besides his people. He was sent to them and was thus sent to humanity as a whole, as they were his people. Shaykh Ibn ‘Uthaymeen 
said in Sharh Al-‘Aqeedah As-Saffaareeniyyah: "If someone asked, Was Nooh not sent to all people in his time?, the answer is: Yes, he was sent to all people in his time; however, there were no other nations except that nation and he was thus sent to his people. Allaah The Almighty says (what means): {Indeed, We sent Nooh to his people, [saying], "Warn your people before there comes to them a painful punishment."} [Quran 71: 1] Humans at that time were not so many as to branch out into different ethnicities. Therefore, Nooh was sent to his people only. In fact, the people were few and Nooh was sent to them and he was thus sent to his people in particular." [End of quote]
When the Shaykh spoke about the Prophet Muhammad, sallallaahu ‘alayhi wa sallam, being distinguished with being sent to all people while all other Prophets were sent specifically to their own peoples, he said: "This cannot be argued through the case of Nooh because the people during his time were his people. The people at that time were a few and were not of different nations. Thus, he was sent to people in general; for people during that time were not of different nations. Therefore, those who did not believe in him were destroyed and those who remained with him on the ship became the fathers of all mankind, as Allaah The Almighty says (what means): {And We made his descendants those remaining [on the earth].} [Quran 37: 77] It is referring to the descendants of Nooh. This refutes the argument of some scholars that Nooh was sent to all the people of the earth. The rebuttal is that all the people on the earth were his people during that time and there were no other people. However, during the time of the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, there were other peoples. There were the Persians, Romans, Berbers and others. The Prophet Muhammad, sallallaahu ‘alayhi wa sallam, was sent to all of them." [End of quote]
Al-Qustalaani said in Irshaad As-Saari: "The answer is that Nooh was sent to the people of the earth because in reality they (all the people of the earth) were his people unlike the universality of the prophethood of our Prophet Muhammad, sallallaahu ‘alayhi wa sallam, for he was sent to his people and other nations."
Al-Haafith Ibn Katheer said in Qasas Al-Anbiyaa': "When corruption and idol worship spread throughout the earth, Allaah Almighty sent His slave and Messenger Nooh to invite people to worship Him alone, apart from any partners and forbid the worhsip anything besides Him. He was the first messenger Allaah, The Almighty, sent to the people of the earth. Abu Hurayrah 
related that the Prophet, sallallaahu ‘alayhi wa sallam, said in the 'Hadeeth of the intercession': “…they will come to Nooh and say: O Nooh, you are the first Messenger Allaah sent to the people of the earth and Allaah called you a grateful servant…”
For more benefit, please refer to Fatwa is the second father of humanity">8588.
Allaah Knows best.