According to Mary Kelaita and Liliana Cortés-Ortiz, individuals of mixed ancestry who share most of their genome with one of the two species are physically indistinguishable from the pure individuals of that species.
Howler monkey research "suggests that the lack of strong evidence for hybridization in the fossil record does not negate the role it could have played in shaping early human lineage diversity."
Liliana Cortés-Ortiz: "The implications of these results are that physical features are not always reliable for identifying individuals of hybrid ancestry. Therefore, it is possible that hybridization has been underestimated in the human fossil record".
Klevius comment: This is why so many have fallen in the "modern humans from Africa" trap despite the overwhelming cultural and genetic evidence pointing to cold Eurasia that Klevius uses for his successful theoretical framwork on how the modern human was born.