Assalam o alaikum, I had read this hadith from your site The Prophet said: "The Prophet Abraham circumcised himself after he had passed the age of eighty years and he circumcised himself with an aze." I have heard that male circumcisation is far older than this and it was found in the form of painting in the caves during stone age and also in egyptian civilization. Here in this link http://uncyclopedia.org/wiki/Stone_Age#Modern_Significance They have written in the article that "It is speculated by many that a departure from characteristic practices of the stone age, known otherwise as 'trendy thinking', have eschewed a step towards cultural prosperity. A striking example of such modern departures include (but are not limited to) subjugation of male infants to a ritualistic procedure known as circumcision (Tsuba, 2005)" My question is if Abraham(AS) was the first person according to be circumcised, then how come circumcision was present in stone age? Can you please explain this?

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 is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

The Prophetic narration about the circumcision of the Prophet Ibraaheem is reported by Al-Bukhari, Muslim, and others . However, the narration did not mention that Ibraaheem was the first to be circumcised, rather it just stated: ''…Ibraaheem, was circumcised at the age of eighty."  Even the Fatwa to which you referred in your question does not say that he was the first person to be circumcised. Moreover, we have neither come across an authentic or a weak narration which states that Ibraaheem was the first person to be circumcised.

The statement that he was the first person to be circumcised was said by Sa'eed Ibn Al-Musayyib but not a saying of the Prophet . 

Moreover, had there been an evidence that the Prophet said so, it would have been an obligation to believe in it and give it preference over what you mentioned that there are painting which prove that the circumcision existed before the era of Ibraaheem . That is because the statements of the Prophet are revelation from Allaah, the Creator of all centuries; Allaah Says (what means): {Nor does he speak of (his own) desire. It is only an Inspiration that is inspired.}[Quran 53:3-4], whereas the indication of the paintings to circumcision is uncertain. It may well be that these paintings refer to something else other than circumcision but relate to the place of circumcision. Therefore, these paintings cannot take precedence over the revelation.

Finally, it is not possible to determine with absolute certainty that these paintings were before the era of Ibraaheem . 

Allaah Knows best.