There never was an evidence-based reason to believe that Neanderthals could not speak. The idea originated in the need to portray them as a “less evolved” human species. (It is not even clear, now that their genome is being mapped, that they even were a separate species.)
Dediu and Levinson review all these strands of literature and argue that essentially modern language and speech are an ancient feature of our lineage dating back at least to the most recent ancestor we shared with the Neandertals and the Denisovans (another form of humanity known mostly from their genome). Their interpretation of the intrinsically ambiguous and scant evidence goes against the scenario usually assumed by most language scientists, namely that of a sudden and recent emergence of modernity, presumably due to a single — or very few — genetic mutations. This pushes back the origins of modern language by a factor of 10 from the often-cited 50 or so thousand years, to around a million years ago — somewhere between the origins of our genus, Homo, some 1.8 million years ago, and the emergence of Homo heidelbergensis. This reassessment of the evidence goes against a saltationist scenario where a single catastrophic mutation in a single individual would suddenly give rise to language, and suggests that a gradual accumulation of biological and cultural innovations is much more plausible.
Colour emphasis added.
This is a classic shell game. Transferring the development of language back a million years does not make it a less “catastrophic” event, in terms either of its origin or consequences.
In any event, human language cannot just develop slowly over hundreds of thousands of years. We either achieve communication or we don’t. When we can’t somehow interpret the signals, we soon stop listening. Not in 100,000 years. In a few minutes. And the signal system dies, as a system.
Perhaps some sense of this can be gained from the fact that, when script writers write lines in English for “the cave man”, they often leave out grammatical adornments like definite and indefinite articles (“the,” “a,” and “an”) and other subtle indicators of meaning—indicators that many equally functional languages do not use or need (because they use other ways of conveying subtle meanings).
And how do we know that the “cave man” could not convey subtle meanings? Well, because… because… Darwin explained it all, you see… read Darwin, believe Darwin… Soak yourself in Darwin…
Journal: Dan Dediu, Stephen C. Levinson. On the antiquity of language: the reinterpretation of Neandertal linguistic capacities and its consequences. Frontiers in Psychology, 2013; 4 DOI: 10.3389/fpsyg.2013.00397
See also: Neanderthal artwork found: “Academic bombshell” obliterates “lesser human” theory?
What’s really at stake in the Neanderthal art controversy: The racist implications of Darwin’s theory