Why do some scientists consider Homo neanderthalensis to be part of the species Homo sapiens?

Some scientists consider Homo neanderthalensis to be part of the species Homo sapiens due to genetic evidence showing interbreeding between Neanderthals and early modern humans, which indicates they are closely related. This genetic exchange suggests that Neanderthals contributed to the gene pool of contemporary humans, leading some to classify them as a subspecies rather than a separate species. Additionally, similarities in tool use, social behaviors, and cognitive abilities further support the idea of Neanderthals being part of the broader Homo sapiens lineage.