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Flipper's Sponge Crew: contexts of cultural adaptations, transmission and social networks

Despite having several topics to post on lined up, my first piece on The Rocks Remain has been hijacked... by dolphins.

While blearily looking at my Twitter feed this morning I saw a great Nature Communications paper (open access!) that @paleophile had tweeted. It reports on results from a long-term study headed by Janet Mann on the social networks of a community of 105 bottlenose dolphins from Shark Bay, Western Australia.

These are already a famous group of marine mammals, being one of the best studied examples of tool-using in non-human animals. Some dolphins at Shark Bay have developed a method for hunting in rocky channels   by using a type of locally-growing basket-shaped sponge. By wearing this on their beaks, they are protected while foraging over rough surfaces; the sponge also serves to disturb fish that are not detectable to dolphins using their major senses, echolocation and vision.

Juvenile female sponger.
"What a sponger!" Photo by Ewa Krzyszczyk; http://www.monkeymiadolphins.org Used under creative commons
The headline finding of the paper is that the dolphins that perform sponging (particularly females) appear to form social cliques with each other. The researchers make a comparison with the way that humans tend to prefer the company of those sharing their own sub-cultural contexts; think of the metallers all hanging out together to discuss Nine Inch Nails behind the school buildings (ok, I'm ageing myself here).

While my still waking-up mind found the idea of dolphin "spongers" pretty comical, I decided to blog about this research because it intersects with things I've been working on to do with Neanderthal 'subcultures'. Yes, I manage to find a Neanderthal link with anything.

The first thing I find interesting is that although sponging might seem an to give an adaptive advantage in allowing certain individuals to find more prey and reduce chance of injury, only a small percentage of the total population frequenting Shark Bay are spongers. This is probably because sponging is quite a solitary activity, often done at some distance from others adults, in clear contrast for example to chimpanzee nutcracking. Yet, sponging dophins are often not completely alone, as females are accompanied by their calves, who seem to learn the skill by the age of around 3 years. This is a perfect example of vertical cultural transmission (parent to offspring), with apparently no horizontal transmission at all. However, as with chimpanzees and nut cracking, some dolphins with a sponging mother never pick up the habit, suggesting either there may be some subtle element of teaching involved to successfully develop the skill, or that some dolphins cognitively don't 'get' it.



The researchers show that sponging dolphins are more solitary than others, and in particular, female spongers. It sounds like the combination of environmental context stimulating a novel behaviour (sponging) has also led to a novel social stucture: female dolphins spend time away from others while sponging, meaning there is little chance for the skill to spread by observation, and their offspring (especially female) then reproduce this. A subculture of 'loners' is created and maintained generationally.

The paper points out that the spongers are not cut-off from wider dolphin society, and do associate with others, though less often and not in the same way as non-spongers. Again, this is much more pronounced in females (males need to move around over larger areas to form alliances). Yet, if sponging is solitary, then how do fellow spongers recognise each other and affiliate more often (i.e. show homophily), as the paper demonstrates they do? It may be due to geographical proximity, as spongers show a clear spatial grouping for their averaged movements, around the area of the deep channels. It may also be kin-related: dolphins are socially similar to their parent, so offspring of spongers will tend to follow the same lifestyle.

So where do Neanderthals fit in? We still know embarrassingly little about the actual social structures of these hominins. This is simply because it's a very difficult thing to pick apart, especially with the coarseness of the evidence we usually are dealing with in the Middle Palaeolithic. Dolphins live in open communities, and display high fission-fusion in terms of their relationship dynamics. This is very reminiscent of the classic way human hunter-gatherers are described, although the extent of fission-fusion varies hugely and is probably linked to environmental context.

Although there's always a risk of simplistic correlation, we know that Neanderthals were living a hunting and gathering lifestyle, and researchers frequently draw analogies with extant or historical peoples living the same way in an attempt to consider fundamentals such as group size. I think several of the results in the paper are relevant here. It shows that despite a technological innovation being adaptive, it may not spread as widely as we might expect, because the behaviour itself has an effect on the levels of social interaction. If some cultural or technological skills are by their nature solitary, then although they may endure locally for some time, they may never become common, and therefore run the risk of also becoming culturally extinct.

The discussion about the structure of dolphin society within Shark Bay, with large gender differences in interactivity is fascinating. Males form small alliances and disperse widely, following diverse and generalised hunting methods. Females, probably because they need a greater input of resources while raising offspring for several years, are more likely to demonstrated specialised food procurement techniques that are habitat-specific, and to range less. I'm wondering whether our notions of Neanderthal social structure, as based on modern and historical hunter-gatherers, might be a little too 'nuclear family'. Perhaps groups structured around age and gender might explain some of the variety in the record, especially the lack of 'home' sites. If females were living in loose networks, providing food for themselves, and in a different manner to wide-ranging alliances of males, this could produce highly mobile, short-term occupations by small numbers of individuals. At sites with exceptional preservation of occupational layers, such as Abric Romani, Spain, this is exactly what we do see: small hearths dotted around the rockshelter, but apparently not occupied at the same time. Most frequently, these are interpreted as representing small family units camping for a few nights; perhaps we need to think outside the 'family' box.

An example of a Neanderthal 'subculture': a bout coupe biface from Castle Lane, Southampton, UK. Image: Author.


The final thing this research potentially links to, is the presence of Neanderthal regional 'sub-cultures' in the Late Middle Palaeolithic (c. 80-40,000 BP). I am intending to write a separate post about this, but suffice it to say, there is clear evidence of spatially delimited trends in Neanderthal tool form. This is not simply in terms of production technique, or reflections of variation in the available stone, but also the style of artefacts (and I used that word advisedly). How and why this occured is something I'll be covering later, but the example in this paper of how the extent of novel and adaptive cultural adaptations can be strongly limited by their contexts of use and impact on social networking, is really intriguing.

These are just some thoughts, and I'm not sure they make much sense (it would mean even greater gender segregation than in chimpanzees, actually more like elephants or lions). There are also occasional examples of sites that do seem to show larger numbers of individuals were present together, including the amazing open-air site of La Folie, France. But even if the idea of a gendered Neanderthal social structure is a flight of fancy, I've enjoyed having my morning diverted by dolphins.

Reference:
Mann, J., Stanton, M.A., Patterson, E.M., Bienenstock, E.J. and Singh, L.O. 2012. Social networks reveal cultural behaviour in tool-using using dolphins. Nature Communications 3, Article 980 doi:10.1038/ncomms1983

Comments

Ian Parry said…
We always seem to compare Neanderthals to 'Us' past or present and the case is that we don't have all the information about what 'We' were doing in any particular time, place or circumstance or what a present day group of hunter gatherers may be doing.

Thank you for an interesting blog(essay)

Ian Parry
Thanks for your comment Ian, and glad you enjoy what I write!

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