The discussion centers on the concept of subspecies within Homo sapiens sapiens, emphasizing that there are no extant subspecies aside from Homo sapiens idaltu. The Neanderthals, once considered a subspecies, are now classified as a separate species, supported by molecular evidence from the Neanderthal Genome Project. Interbreeding between Neanderthals and modern humans has occurred, but it is debated due to potential DNA contamination in samples. The presence of Neanderthal genes in modern human genomes does not appear to create reproductive barriers. The conversation highlights the complexity of defining subspecies and the implications for fertility among them, ultimately concluding that the percentage of fertile offspring among subspecies is moot since no true subspecies exist today.
