Response to the specious argument that the existence of primitive tribes who do not believe in God undermines the idea that belief in the existence of God is innate in humans
Question

If belief in Allah is innate, then why does this Amazonian tribe called Pirahã does not even have basic beliefs in a Creator? Some atheists are using this as an evidence that religious beliefs are not natural to human beings...
Praise be to Allah.Firstly:
Humans have an innate knowledge that they have a Creator and Lord. This is one of the clearest proofs for the existence of Allah, may He be exalted.
Shaykh Ibn ‘Uthaymin said:
The innate knowledge that Allah exists is stronger than any other evidence for one who has not been misled by the devils. Hence Allah, may He be exalted, says (interpretation of the meaning):
{[Adhere to] the natural disposition that Allah instilled in humankind} [Al-Rum 30:30],
after saying: {Adhere exclusively and sincerely to the true faith of monotheism}. So sound human nature testifies to the existence of Allah, and no one can turn away from this innate knowledge except one whom the devils have misled. In the case of one whom the devils have misled, there is a strong reason why this innate knowledge is no longer effective in his case."(Sharh al-Safariniyyah, p. 31).
For information on the evidence for the existence of Allah, may He be exalted, please see the answer to question no. 26745 .
The fact that there are people who deny the existence of Allah, may He be exalted, or who associate others with Him, does not mean that they have no innate knowledge of Allah. Rather it means that they have deviated from this innate knowledge, as a result of the devils among humankind and the jinn misleading them, as is mentioned in the hadith qudsi: “I have created all My slaves with the inclination to worship Me alone, but the devils come to them and turn them away from their religion. They forbid to them that which I have permitted to them, and they tell them to associate others with Me for which I have not sent down any authority.” Narrated by Muslim (2865).
Hence the number of these deniers is very few in relation to the total population of the earth; the entire population has innate knowledge that they have a Lord, even if some of them associate others with Him or worship a lord who is not Allah.
Even if this innate knowledge is undermined by the influence of parents, forefathers, traditions and one’s environment, it often appears at times of hardship, so a man will turn to his Lord even if he has been arguing about His existence!
There is an interesting Western proverb which says, “There are no atheists in the trenches [of the battlefield].”
Many atheists confirm this innate knowledge of Allah and that it is instilled in every soul, even if they do not call it by this name (fitrah).
For more information on that, please see the book Shumu‘ al-Nahar by Ustadh ‘Abdullah al-‘Ujayri, p. 31 ff.
Dr al-Bashir ‘Isam says: One of the most famous counterarguments to the evidence of innate knowledge of Allah is the view of some of them, who say that if knowledge of Allah and His existence is instilled in human nature, then why are there people who deny His existence?
The answer is: those who affirm the existence of Allah are only those whose human nature is still sound and has not deviated. As for those who were exposed to strong specious arguments, to the point that they uprooted sound human nature from their souls, they will need to study the rational evidence and scientific proof.
For sound human nature to be corrupted and changed is not an impossible or far-fetched notion, for a person may grow up in a deviant and misguided environment, so he will be exposed to many deviant ideas that push him away from the straight path.
Ibn Taymiyah said: “Believing in and acknowledging the Creator is something innate and is instilled in the souls of all people, even though some people may be subjected to that which corrupts their sound human nature to the point that they need to reflect deeply on the matter so as to learn again about their Creator.”
There is another answer to this question, which is: those who go against their sound human nature and deny the existence of the Creator are very few among humanity throughout history, as noted above.
Moreover, many of them may deny the existence of Allah outwardly, even though they may inwardly believe in His existence, as Allah, may He be exalted, tells us about Pharaoh and his people and the way in which they reacted to the signs of Allah, may He be glorified. Allah says (interpretation of the meaning):
{They rejected the signs, although in their hearts they were certain that they were true, out of wickedness and arrogance} [Al-Naml 27:19]. End quote.
It says in his article: It is interesting to note that the view that belief in the existence of Allah is instilled in human nature is not something unique to the scholars of Islam; rather it is something that is affirmed by a group of modern philosophers.
One of them, for example, is the American philosopher Alvin Plantinga, who insists that faith is something natural, and that belief in the existence of God is like belief in some other basic concepts, such as the belief that others have rational thought like ours, and the belief that our senses are real, and that the whole is greater than the part. End quote.
See the rest of his article for further discussion of the idea that there is a great deal of evidence to prove that knowledge of Allah is innate in human beings.
Finally, we may note that what we have read about the tribe mentioned is that they are very few in number, and that they live a primitive life. We have not come across anything to suggest that they deny the existence of the Creator. There is a difference between a person not being aware of a particular religion, not worshipping Allah in some way or another, and not knowing Allah by His names and attributes, on the one hand, and denying the existence of the Creator, on the other hand.
Secondly:
Our advice to you is to seek knowledge and to avoid reading specious arguments that may corrupt your heart and lead you to doubt, unless you are very well versed in knowledge, in which case you may examine specious arguments in order to refute them.
And Allah knows best.