Whilst Homo sapiens is defined by its biology, if one were forced to identify their most important attribute then their anatomy would not be it. No, it is our behaviour which truly sets apart from other creatures.
Although our body is a highly derived object with surprisingly derived adaptations, it is how we behave that most people look to when talking about our unique traits. Thus identifying when modern behaviours emerged in our lineage has long been an area of great interest for EvoAnth.
Despite this importance, it’s been a somewhat neglected topic on this blog. Whilst I’ve discussed various aspects of modern behaviour in the archaeological record, I haven’t really put into a wider context.
Then I bumped into a recent paper (for those of you keeping track it’s published by the same guy who discovered the language groups of our ancestors) discussing the current state of our understanding about the emergence of modern behaviour and it seemed like the perfect opportunity to correct this shortfall.
So ladies, gentlemen and variations thereupon, without further ado I present to you a brief introduction to what we know about the emergence of modern behaviour.
First, I suppose it’s best to define what people view as modern behaviour (creatively titled “behavioural modernity”). There isn’t really a universal criteria, but generally speaking it consists of
Exploitation of coastal environments; greater complexity of food gathering procedures, such as the use of nets, traps, fishing gear; complex use of fire for cooking, food conservation; ecosystem management; producing and hafting stone tools; invention of specialized tool-kits to adapt to extreme environments; higher population densities approaching those of modern hunter–gatherers; complex tools, the styles of which may change rapidly through time and space; structures such as huts that are organized for different activities; long-distance transport of valued materials; formal artefacts shaped from bone, ivory, antler, shell; musical traditions; sea crossing and navigation technology; personal ornamentation in the form of body painting and personal ornaments; art, including abstract and figurative representations; evidence for ceremonies or rituals; complex treatment of the dead
The real focus on the emergence of modern behaviour started back when all archaeology took place in the Western world. There, people started to notice that the Upper Palaeolithic was very distinct from the periods which had preceded it as it contained a whole suite of new behaviour.
This discovery was quickly termed a “revolution” and identified as the moment at which modern behaviour emerged. Modern cognition, language, imagination, art, religious beliefs and so forth all seemed to appear overnight ~35,000 years ago. Was this the moment at which humanity really got going?
Since then several new finds have been added to the picture and archaeological investigation has expanded into Africa which has added a whole new dimension to this story. The result of this is that nowadays there are 4 basic hypotheses which account for the emergence of behavioural modernity.
- ~50,000 years ago – just before the Upper Palaeolithic emerged – there was a brain mutation amongst a population of anatomically modern humans that restructured, altered or in some other way improved their cognitive ability and enabled them to engage in modern behaviour.
- ~80,000 years ago – when Upper Palaeolthic-esque finds appear in the African record – there was a brain mutation which improved human cognition. This was responsible for not only the emergence of modern behaviour but also our ability to leave Africa.
- As populations grow there is an increase in the rate at which they innovate. At some point in the past human populations crossed a critical threshold that led to a series of innovations which developed into modern behaviour.
- All the cognitive abilities were in place by the time neanderthals and humans had diverged, it was just a combination of climate, demography (see hypothesis 3) and other such factors which prompted them to use these abilities to develop what is now known as modern behaviour
The obvious question (which is not begged in any way) then, is which of these 4 hypotheses is correct?
Well, several of the supposedly “modern” behaviours appear at greater ages than early research suggested.
- Costal exploitation now seems to date to ~90 kya (thousand years ago) based on harpoons found in Africa. Also, neandertals seems to have participated in this also, suggesting it (or the cognitive processes required) may have emerged even before that.
- Complex fire use appears to date to ~75 kya based upon tools that were made with the assistance of fire.
- Complex tools – including blades – appear as early as ~145 kya, although they frequently disappear and reappear throughout this time. Further, neanderthals also produced similarly complex tools
- Hafted tools are first identified ~186 kya
- Burials appear as early as ~100 kya
- Personal ornamentation appears ~100 kya with the use of pigments occurring even early, at ~200 kya (although they might not have been used for symbolic reasons)
Thus hypotheses 1 & 2 seem to be refuted by this wealth of older dates (unless of course, one redefines behavioural modernity to exclude these aspects but that seems a rather dishonest way of supporting them) and the paper itself is unwilling to decide whether 3 or 4 is more accurate.
I personally suspect number 4, since it posits a range of explanations and so avoids the reductionism and oversimplification that is often present in science.
At any rate, we can rather safely say that it isn’t the result of a brain mutation 50 or 80 kya.
|d’Errico F, & Stringer CB (2011). Evolution, revolution or saltation scenario for the emergence of modern cultures? Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 366 (1567), 1060-9 PMID: 21357228|