Hard to tell, since we know so little about their soft tissues. But they probably had fur.
Were the Neanderthals as furry as bears? The question was raised by one of my readers, and I’ll try to reply at length in this post.
There are three lines of argument:
Lack of tailored clothing
Neanderthal sites show no evidence of tools for making tailored clothing. There are only hide scrapers, which might have been used to make blankets or ponchos. This is in contrast to Upper Paleolithic (modern human) sites, which have an abundance of eyed bone needles and bone awls (Hoffecker, 2002, pp. 107, 109, 135, 252). Moreover, microwear analysis of Neanderthal hide scrapers shows that they were used only for the initial phases of hide preparation, and not for the more advanced phases of clothing production (Hoffecker, 2002, p. 107).
The counter-argument is that some human groups, notably the Yaghan of Tierra del Fuego, have lived in sub-arctic environments with little clothing.
Human body louse
The human body louse (which lives in clothing) seems to have diverged from the human head louse with the advent of modern humans. This dating is based on a comparison of the two louse genomes:
The results indicate greater diversity in African than non-African lice, suggesting an African origin of human lice. A molecular clock analysis indicates that body lice originated not more than about 72,000 ± 42,000 years ago; the mtDNA sequences also indicate a demographic expansion of body lice that correlates with the spread of modern humans out of Africa. These results suggest that clothing was a surprisingly recent innovation in human evolution.(Kittler et al., 2003)
A more recent analysis places the origin of body lice at 83,000 to 170,000 years ago (Toups et al, 2011). The authors conclude: “Our estimate for the origin of clothing use suggests that one of the technologies necessary for successful dispersal into colder climates was already available to AMH prior to their emergence out of Africa.”
There is nonetheless some controversy over the phylogenetic status of these two kinds of louse. Light et al. (2008) argue that there is far too much genetic overlap between them and that they cannot be considered “genetically distinct evolutionary units.” This point has been reiterated by Li et al. (2010):
While being phenotypically and physiologically different, human head and body lice are indistinguishable based on mitochondrial and nuclear genes. As protein-coding genes are too conserved to provide significant genetic diversity, we performed strain-typing of a large collection of human head and body lice using variable intergenic spacer sequences. Ninety-seven human lice were classified into ninety-six genotypes based on four intergenic spacer sequences. Genotypic and phylogenetic analyses using these sequences suggested that human head and body lice are still indistinguishable. We hypothesized that the phenotypic and physiological differences between human head and body lice are controlled by very limited mutations.
This is a recurring problem when one examines two species or subspecies that have recently diverged from each other. The only genes that have diverged are those whose variants clearly differ in adaptive value between the two environmental settings—in this case, head hair and clothing. It is only with time, and reproductive isolation, that differences will develop at other gene loci.
In the meantime, lice—like humans—exhibit the apparent contradiction of distinct phenotypic differences co-existing with very fuzzy genetic differences.
Finger bone ridges
A third reason is given by Cochran and Harpending (2009):
We don’t yet know for sure, but it seems likely that, as part of their adaptation to cold, Neanderthals were furry. Chimpanzees have ridges on their finger bones that stem from the way that they clutch their mother’s fur as infants. Modern humans don’t have these ridges, but Neanderthals do.
Cochran, G. & H. Harpending (2009). Neanderthals Steve Sailer’s iSteve Blog, January 10, 2009
Hoffecker, J.F. (2002). Desolate Landscapes. Ice-Age Settlement in Eastern Europe. New Brunswick: Rutgers University Press.
Kittler, R., M. Kayser, & M. Stoneking. (2003). Molecular Evolution of Pediculus humanus and the Origin of Clothing, Current Biology, 13, 1414-1417.
Li, W., G. Ortiz, P-E. Fournier, G. Gimenez, D.L. Reed, B. Pittendrigh, D. Raoult. (2010) Genotyping of Human Lice Suggests Multiple Emergences of Body Lice from Local Head Louse Populations. PLoS Negl Trop Dis 4(3): e641.
Light, J.E.,M.A. Toups, & D.L. Reed. (2008). What’s in a name: The taxonomic status of human head and body lice, Molecular Phylogenetics and Evolution, 47, 1203-1216.
Toups, M.A., A. Kitchen, J.E. Light, & D.L. Reed. (2011). Origin of Clothing Lice Indicates Early Clothing Use by Anatomically Modern Humans in Africa, Molecular Biology and Evolution, 28, 29-32.