Neanderthal language has long been a contentious topic, with some authors denying any possibility of language outside Homo sapiens, and others supporting a long gradual emergence of language including our relatives.

The 21st century has seen a rapid increase in the availability of relevant evidence from different fields, notably archaeology and palaeogenomics.

Many of the various types of archaeological finds that have traditionally been regarded as evidence of behavioral modernity and sapiens-level cognition, including language, have been found associated with Neanderthals. This includes pigments, personal ornaments such as pendants, and engravings on both cave walls and portable objects. Neanderthals were also capable of technological feats ranging from seafaring to the manufacture of glue. There are no major archaeologically visible differences between Neanderthals and H. sapiens living at the same time, and thus no grounds for postulating major cognitive differences.

After the demise of the Neanderthals, the cultural development among sapiens did take off. But language must predate the splitting of sapiens into multiple separate populations in different parts of the world—which predated Neanderthal extinction.

The sequencing of the full Neanderthal genome provided a wealth of genetic data informing the issue of Neanderthal language. Some of the genetic changes associated with language abilities in modern humans were present also in Neanderthals. The availability of mass genetic screening has also made it possible to locate living people who carry Neanderthal alleles of various language-relevant genes, generally without any obvious impact on their language abilities.

The speech-related anatomy of Neanderthals is not identical to that of sapiens. But there is nothing in Neanderthal anatomy that precludes the possibility of speech, though their vowel space may be restricted. In any case, language need not be vocal; Neanderthal sign language remains a possibility.

In summary, a strong case can be made for Neanderthals having had some form of language, if not necessarily identical to modern languages.