Two sites of the Neandertal-associated Middle Paleolithic of Iberia, dated to as early as approximately 50,000 years ago, yielded perforated and pigment-stained marine shells. At Cueva de los Aviones, three umbo-perforated valves of Acanthocardia and Glycymeris were found alongside lumps of yellow and red colorants, and residues preserved inside a Spondylus shell consist of a red lepidocrocite base mixed with ground, dark red-to-black fragments of hematite and pyrite. A perforated Pecten shell, painted on its external, white side with an orange mix of goethite and hematite, was abandoned after breakage at Cueva AntÃ³n, 60 km inland. Comparable early modern human-associated material from Africa and the Near East is widely accepted as evidence for body ornamentation, implying behavioral modernity. The Iberian finds show that European Neandertals were no different from coeval Africans in this regard, countering genetic/cognitive explanations for the emergence of symbolism and strengthening demographic/social ones.
The main issue here are conditional probabilities. We have a thick network of facts which allow us to infer aspects of modern human nature from material objects. Granted, those inferences are not always correct and strongly conditioned upon theoretical frameworks. Consider the model of the "peaceful Maya," which was shattered once the Maya codices were thoroughly translated. In hindsight the fact that the Maya were a warlike people who engaged in human sacrifice wasn't too surprising, but the clarity was conditional upon expectations. People can often see what they want to see.
As for the idea that Neandertals may not have been cognitively so different, I am more open to that than I would have been years ago. If we had a better understanding of neurogenomics and more Neandertal samples perhaps ancient DNA extraction might be able to resolve the mystery, but for now we need to go on indirect evidence. The Neandertals had larger cranial capacity than modern humans, so it sure wasn't an issue of brain quantity. There is evidence of cultural hybridization during the ChÃ¢telperronian, while the disparate responses of Meiji Japan and Late Qing China to the European threat in the late 19th century shows that even among behavioral modern humans some societies can absorb and adapt via diffusion while others can not. The different responses of the Japanese and the Chinese had more to due with historical contingency than human nature.
Update: Here's a deeper review.
Citation: JoÃ£o ZilhÃ£o, Diego E. Angelucci, Ernestina Badal-GarcÃa, Francesco d'Errico, FlorÃ©al Daniel, Laure Dayet, Katerina Douka, Thomas F. G. Higham, MarÃa JosÃ© MartÃnez-SÃ¡nchez, Ricardo Montes-BernÃ¡rdez, Sonia Murcia-MascarÃ³s, Carmen PÃ©rez-Sirvent, Clodoaldo RoldÃ¡n-GarcÃa, Marian Vanhaeren, ValentÃn Villaverde, Rachel Wood, and Josefina Zapata, Symbolic use of marine shells and mineral pigments by Iberian Neandertals, doi:10.1073/pnas.0914088107
In "The Coming of the Age of Iron" by Wertime et. al. it is argued that ochre pigments (which are iron oxide) were a precursor of iron smelting.
for now we need to go on indirect evidence
Minor point, but neurogenomic evidence would be indirect as well, no?
I'm not sure neurogenomics would solve this problem. Perhaps many of our cognitive abilities are artifacts--they exist because of certain types of acculturation that are relatively stable over long periods of time. I am not sure that small isolated bands of Homo sapiens would necessarily make representational art, or use language much, etc. Neanderthals lived at extremely low population densities--I think the estimate is under 10,000 individuals in Europe--making cultural transmission and development extremely difficult. It could be purely cultural constraints that kept them from exploiting certain resources or establishing larger groups, which ultimately hampered cultural development. So even knowing how the genetic differences would contribute to cognitive differences in a modern human might not tell us much about Neanderthal cognitive abilities. That said, I wish someone would get some better Neanderthal DNA.
Or, maybe Neanderthals really did lack the neural substrate for the types of plasticity that allow for such a broad spectrum of acculturated cognitive abilities. Deacon would say that all human cognition is built on an ability to freely manipulate mental symbols--since some great apes show glimmers of being able to do this, particularly if they start young, it seems likely that Neanderthals had this capacity as well.