The Neanderthal is an extinct member of the Homo genus that is known from Pleistocene specimens found in Europe and parts of western and central Asia. Neanderthals are either classified as a subspecies of humans (Homo sapiens neanderthalensis) or as a separate species (Homo neanderthalensis). The first proto-Neanderthal traits appeared in Europe as early as 600,000–350,000 years ago. Proto-Neanderthal traits are occasionally grouped to another cladistic 'species', Homo heidelbergensis, or a migrant form, Homo rhodesiensis. By 130,000 years ago, complete Neanderthal characteristics had appeared. These characteristics then disappeared in Asia by 50,000 years ago and in Europe by 30,000 years ago.
Neanderthal cranial capacity is often thought to have been as large or larger than modern humans, indicating that their brain size may have been the same or greater; however, a 1993 analysis of 118 hominid crania concluded that the cranial capacity of H.s. neandertal averaged 1,412 cc (86 cu in) while that of fossil modern H.s. sapiens averaged 1,487 cc (91 cu in). On average, the height of Neanderthals was comparable to contemporaneous Homo sapiens. Neanderthal males stood about 165–168 cm (65–66 in) and were heavily built with robust bone structure. They were much stronger, having particularly strong arms and hands. Females stood about 152–156 cm (60–61 in).
A Jewish-Americanwriter contemplated his failed first marriage, and wondered if it might have worked in some alternate timeline. After considering and discarding a number of possibilities, he imagined a world where Homo sapiens hadn't made their way into Europe and wiped out Neanderthal. He again concluded that his ex-wife's Neanderthal analog and his analog would have had the same fights. At this point, the writer realized how silly this was, since he was perfectly happy with his second wife in a marriage that had worked for forty years, but his inability to accept that he'd done anything wrong led him to one last thought-experiment.