The same distinction between theological and scientific considerations applies to the belief that the people on Earth today are descended from Adam. This is, as we have determined, the position of classical Islamic theology. Anyone who believes this cannot doubt that Adam’s descendants have diversified in color, stature, and physical appearance as they spread throughout the Earth. In the absence of any unequivocal textual evidence describing Adam’s earliest descendants in detail, there would be no way to gauge the extent or rate of genetic and phenotypic change that has taken place among Adam’s later progeny. Therefore, scriptural evidence cannot be used by theologians to indicate whether Adam’s earliest descendants would have been classified biologically as Homo sapiens or possibly as some earlier human species. This means that theologians would not attempt answers to questions like whether Homo neanderthalensis were from Adam’s descendants, any more than they could argue whether or not creatures that scientists would classify as being biologically Homo sapiens had already evolved on Earth and were populating it before Adam’s arrival upon it. All the evidence for hominid evolution, up to and including the evolution of Homo sapiens in a direct line of descent, is empirical, and there is nothing in Islamic scriptures that confirms or contradicts the existence of those hominids. Consequently, it is not a matter of religious belief to accept or reject the scientific account of hominid evolution up to and including organisms that are taxonomically Homo sapiens . It remains purely a scientific question. From a scriptural standpoint, it is not possible to determine precisely when Adam and Eve made their appearance on Earth nor whether they may have met any pre-existing hominid species.
Could there have been hominid species prior to Adam? Scripture does not rule it out. Could these hominid species have co-existed with Adam and his descendants? Again, there is nothing explicit from scripture to negate this. Could the descendants of Adam have intermarried with other populations that were already present on Earth? Once again, scripture is silent.38 The theological stance of tawaqquf necessitates that we refrain from affirming or negating such scenarios in the absence of direct scriptural evidence, as all such questions constitute baseless speculation about matters of the Unseen. Addressing such scenarios is of neither scientific nor theological importance since the sacred texts do not bring them up and science does not deal with them.
I also notice that this paper acknowledges the commonalities between this author and @swamidass’s work: