Did better mothering defeat the Neanderthals?
An exciting new series inspired by a major five-year project at Kochi University of Technology in Japan casts new light on how modern humans inherited the Earth. Reviewed by Paul H. Mason.
As the first humans made their way out of Africa some 80,000 years ago they began to occupy territories inhabited by Neanderthals. Their populations ended up overlapping for between 30,000 and 50,000 years, and some male Neanderthals reproduced with human females, evidenced by the fact that up to 4% of modern human DNA has Neanderthal origins but there is no evidence of mitochondrial DNA which is passed exclusively through the maternal line (COSMOS issue 39, p 27). Yet the two groups never merged into a single population. They upheld their distinct cultural practices until eventually Neanderthals were replaced by the invading humans. Scientists still do not know exactly why Neanderthals became extinct. I have long entertained a novel idea: that it was because human mothers, in comparison to their Neanderthal sisters, lavished more attention on their offspring.
This exciting new series is inspired by the research outcomes of a major five-year project at Kochi University of Technology in Japan. It offers some support for my view. “Replacement of Neanderthals” collates a large body of multidisciplinary research on the factors that contributed to the extinction of Neanderthals, including their anatomy, cranial volume, stone tool technology, rituals, climate change and recent discoveries about the genes they carried. The novel theme of this series, though, is the emphasis on learning differences: the authors consider them the most important factor in the replacement of Neanderthals by humans. But while the research series considers cultural transmission from parents to offspring, one key feature of Neanderthal and human social organisation remains strikingly unexplored. What were the gender roles and kinship patterns of these two hominin groups? Evidence to date indicates that Neanderthals were patrilocal, meaning the females went to live with their mate’s family; whereas early modern humans appear more likely to have been matrilocal, the male moved to the female’s family. How would gender dynamics and kinship structure influence the competition between species? Quite dramatically!
Female Neanderthals were physically robust and hunted alongside their men – their fossil bones show that they sustained injury from close-proximity big game hunting. Humans, on the other hand, opted for a greater division of labour. While female Neanderthals were off hunting with the men, female humans spent their time on domestic duties, which included cave painting. Contrary to popular perception, your stone age Michelangelo was more likely to be a Maria, according to a recent study of 40,000-year-old hand stencils reported in American Antiquity. This finding highlights the creative role that female humans played in hunter-gatherer societies, and also has clear implications for the type of mothering they were able to deliver. Recent data published in Nature adds to this picture. Analysis of a fossil tooth from a Neanderthal infant shows that Neanderthal children moved off exclusive breastfeeding at around 7.5 months of age. In comparison, infants in hunter-gatherer societies are not weaned until around three or four years of age. Clearly, female participation in close-range hunting would impact negatively upon child-rearing capacities while lullabies and cave painting would be more conducive to the mother-infant bond.
In my view, the human babies who had more time with their mothers, who were in turn supported by their own families in the task of raising highly dependent, slow-maturing, offspring, found themselves in an ideal learning environment. The mother-infant bond is key to the evolution of language, nonverbal communication and interpersonal emotional skills; the extended childhood increases the duration of learning and innovation.
Was the victory of humans over Neanderthals a result of the long-term benefits of a social structure that more highly valued the mother-infant bond? Firmer evidence is required. However, a stronger understanding of gender dynamics in Neanderthal and human populations will certainly contribute to a comprehensive understanding of human origins.