Thanks to Ed Yong several people on twitter have encountered my post, The point mutation which made humanity. My broader concern which I was attempting to highlight is that too often when we attempt to ascertain the origins of modern human success in relation to our archaic cousins/ancestors we presume that there must be a qualitative species-wide difference. So, for example, it used to be bandied about that a large effect mutation conferred upon the ancestors of modern humans the ability to speak with the fluency which we take for granted. For various reasons that seems less and less plausible.
But even my thin knowledge of archaeology does indicate that what remains plausible is that modern humans exhibited a level of scale in their group-size, as well as extended force projection, and the ability to rapidly traverse difficult territory. It was modern humans who pushed the frontier to Australia and the New World, even if some archaic lineages did brush up against the margins (e.g., Flores). This sort of concerted and somewhat crazy outward projection of numbers probably required greater specialization and integration of the various groups which would have to operate as a unit as they pushed the frontier outward. One way you can increase the flexibility of a group is by increasing the competencies of individual members of the group. So a large subspecies level difference between modern humans and Neandertals might explain why the former could scale up into larger and more effective groups. But another possibility is that a minority phenotype emerged among modern humans, and this phenotype was correlated with a set of strategies and personalities which allowed for improved coordination amongst who lacked the phenotype. A powerful leader with organizational drive. So, for example, the well fed Gauls that confronted Caesar’s legions may well have been more robust on a per person basis than the Romans, thanks to their protein rich diet. But the coordination of the legions, and the discipline of the troops, allowed them to grind away at their until they were crushed. That Republican Roman discipline did not exist in a cultural vacuum. For the clans of Latium to transform themselves into the mega-city of the ancient world there had to be a series of competent leaders such as Scipio Africanus to drive the process forward.
Plots like the one to the left (credit: Luke Jostins) illustrate that there were broad concurrent trends across the human lineage. More recently there have been parallel events such as the emergence of agriculture in distinct hearths after the Ice Age. Perhaps modern human civilization as we understand isn’t such a contingent miracle, and the process was already made nearly inevitable ~5 million years ago as the hominins began to hurtle toward some terminus, yet to be determined? If so, the “human journey” may not exhibit so many biological breaks which can be easily discerned from examining the physique or genomes of modern humans and our archaic relatives. Rather, the great cultural breaks which we can perceive in the physical record may simply reflect rapid shifts driven by a few, and catalyzed by the collective coordination of groups which were turned into the extension of the vision of charismatic leaders.
I don’t really believe the story above. But I do believe it more at this point than the possibility that we can find the gene which is responsible for making us human. And I’m someone who is quite willing to find genes responsible for great things….
Razib Khan’s degrees are in biochemistry and biology. He has blogged about genetics since 2002, previously worked in software development, is an Unz Foundation Junior Fellow and lives in the western US. He loves habaneros.
October 17th, 2011 at 7:29 am
Recent studies show that humans are significantly more prone to cooperation and collaboration than our Chimpanzee cousins. (http://www.sciencedaily.com/releases/2011/10/111013121519.htm) This could explain the ‘coordination miracle’
October 17th, 2011 at 7:44 am
I think you could say many of the same things about the sophisticated colony insects: coordination, combat between rival groups, rapid spread and expansion into new territory, convergent evolution of sociality, etc. At some point the scalability of that particular chemical-signal mediated sociobiological strategy hits its ecological limits. I don’t think the “super-colonies” are actually “coordinated” like the members of a particular hill or hive seem to be.
In mammals social groups the coordination is both chemical and cognitive. What seemed to happen with primates is some kind of significant intra-group social advantage to having a larger Dunbar number which created a selective pressure for ever larger brain capacity, but also increased the potential size of a cohesive social unit which likewise gave a significant inter-group competitive advantage. I don’t think it’s a pure coincidence that military companies have often settled somewhere around this maximum social capacity.
At some point, what must have happened next is the capacity to think in terms of hierarchy and social abstraction. I have my close relatives within a Dunbar group which has a chief. The chiefs also form a group, which has its own leader (albeit with a lot of jostling), etc. I am able to cooperate in a common effort many more people than I could possible know personally. Whoever was first able to organize something larger than a “natural” company-strength unit through the use of this abstraction would eventually defeat all the non-social-abstraction-capable groups.
But I think here’s the key. The only essential step is the abstraction itself – the idea of and capacity for hierarchy. After you have that, there may be no meaningful limit to “scalability” and the size of organizable force. After you see the possibility of making a battalion out of a few companies, it’s just as obvious to do the same thing again to make brigades, divisions, etc. Actually coordinated “super-colonies”. My hunch is that it’s a key ingredient in the recipe for civilization, and human-ish bands without the capacity would inevitably perish.
October 17th, 2011 at 7:51 am
“But another possibility is that a minority phenotype emerged among modern humans, and this phenotype was correlated with a set of strategies and personalities which allowed for improved coordination amongst who lacked the phenotype”
Yes but hasn’t it been argued in books like the 10,000 Year Explosion that it was the bourgeois which had higher fecundity rather than the charismatic military elite who were more likely to be killed in battle rather than to procreate to their maximal extent?
This argues for cultural memes trumping the superior genes of great leaders. Boudica was not any less innately talented than Suetonius, merely less well educated and organized.
Or am I completely missing your point here?
October 17th, 2011 at 9:02 am
“The Way We Are” by Stan Gooch (2000)
“In April 1999 Professor Trinkaus of Washington University announced that fossil finds in Portugal some 25,000 years old proved conclusively that Neanderthal man and Cro-Magnon man had interbred. That of course had long been obvious to anyone with eyes in his head—‘you can observe Neanderthal at any public gathering’ as Oswald Spengler remarked.
…from around 35,000 BP there is a sudden explosion in the complexity and style and use of tools throughout the whole world human community—as also of all aspects of culture. Where, asks McKie, did the modern world suddenly spring from and why? He then states, frankly, that he and the scientific community have no explanations to offer.
…When widely divergent species of animal are crossed and subsequently observed in the laboratory the offspring are frequently found to have inherited conflicting sets of instincts, evolved in their parents’ separate evolutionary pasts.
…[this] is also what occurred when Neanderthal and Cro-Magnon interbred. Now we can understand why our culture has so many established and enduring metaphors, and so many enduring and central storylines, attesting to our ‘double life’: the divided self, the two souls within one breast, the left hand not knowing what the right hand is doing, Cain and Abel, Jekyll and Hyde, Faust. This too is why, for example, we long for true, everlasting love on the one hand—yet hanker for promiscuity and one-night stands on the other,
How could two such diametrically opposed instinctive drives exist side-by-side in terms of any normal evolutionary scenario, within any one single species? Oh, but surely we are not governed by instinct to that extent? Oh, but surely we are. The greater part of our social life and culture is centrally governed by ‘fossil behaviours’ evolved by our ancestors in the distant past. Desmond Morris in particular has written several books on this subject.”
http://www.aulis.com/twothirds2.htm
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“Genomic Antiquities” (Oct 7, 2011)
“It is likely that many human populations are the descendants of modern and archaic hominids. Abi-Rached et al. (p. 89, published online 25 August) examined the HLA-A, HLA-B, and HLA-C genes (which play central roles in immune defense and placental reproduction) of archaic Denisovan and Neandertal individuals and modern humans. Population genetic evidence suggests that interbreeding between archaic and modern hominids introduced an allele of HLA-B that subsequently reached appreciable frequency in some modern human populations. Thus, admixture probably introduced advantageous genetic alleles that may have been involved in shaping the immune system of modern humans.”
https://www.sciencemag.org/content/334/6052/13.1.full
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“US researchers’ discovery promises answers on autism” (Sept 8, 2011)
“Researchers have for the first time identified two biologically different strains of autism…
One group of children – all boys – had enlarged brains and most had regressed into autism after 18 months of age; another group appeared to have immune systems that were not functioning properly.”
http://www.theaustralian.com.au/news/health-science/us-researchers-discovery-promises-answers-on-autism/story-e6frg8y6-1226131763200
October 17th, 2011 at 9:30 am
“The downside of sex with Neanderthals: Some modern humans carry immune genes that originated in Neanderthals and a related species. But these genes may have come at a price” (August 25 2011)
“Paul Norman, a co-author on the paper, put it like this: “There’s enormous genetic variation in people’s immune systems and that can control how different people fight different diseases. This could go some way to explaining why some people are better at fighting some infections than others, but we think it also goes some way to explaining why some people are susceptible to autoimmune diseases.”
http://www.guardian.co.uk/science/blog/2011/aug/25/neanderthal-denisovan-genes-human-immunity
October 17th, 2011 at 10:52 am
I remember those graphs. Sure you can go from Hawks’ reasonably simplest model and add more degrees of freedom, but then you have to compare which is the best.
The funny thing is if you do a moving average, AFAIK then our brains have been shrinking for a considerable time period. YMMV. (You can find that plot on the web too.)
October 17th, 2011 at 11:36 am
A plausible way to measure the “leadership factor” would be to compare societies based upon the degree to which they self-organize, which has been operationalized by some comparative sociologists. The classic example is the POW scenario. The Brits were quick to self-organize – choosing and showing loyalty to a leader chosen on an ad hoc basis who commanded loyalty and effectively managed limited resources. The Yankees faired rather more poorly in this measure. Similar distinctions were noted between units that became POWs in the civil war – those that self-organized swiftly faired better than those that did not with dramatic consequences for those involved surviving or not. Post-disaster response provides similar indicators – the Japanese quickly self-organized into viable communities after its tsunami, Haiti struggled much more mightily.
The trouble is that I’m not very convinced that this is very explanatory of long run prosperity. When climate conditions are good the self-organizers seem to have an edge, but in period of climate shock, the disorganized “barbarians” seem to prevail and civilization collapses for a while.
October 17th, 2011 at 7:03 pm
But I thought all modern humans where painters, sculptors, musicians, and seamstresses when they arrived in Europe 40,000 ya?
Evidently, division of labor as an accepted social structure was one factor of success, and I doubt that was just cultural. At any rate, it meant that even a smallish group could be much more than the sum of its components.