Male circumcision was not invented by Abraham or the Hebrews, but has been around far longer.
Archeologists say that the early evidence indicates that Africans, Aborigines, and Ancient Near East peoples practiced circumcision for 10,000-15,000 years before the era of the Hebrews.
According to Dr. Gerald Larue (professor emeritus of Biblical history and archeology at UCLA), scholars have discovered indisputable evidence of circumcision in Egyptian tomb artwork and bodies that has been dated as early as the 40th century BC (this would be around 2,000 years before the date that conservative bible scholars say Abraham lived in). (1)
What is also fascinating is that when Columbus reached the New World, he found many of the local natives were circumcised (2), meaning that circumcision may have developed in multiple cultures independently, or that it was such an ancient practice that the people who crossed into the Americas some 20,000 years ago had brought the practice with them.