Addendum to Gardening in Eden

”Archaic” Homo sapiens subspecies were widespread across Africa and Eurasia. Not all looked like Neanderthals – many were clearly much more like anatomically modern Homo sapiens sapiens. This describes the specimens recovered in Israel at Misliya cave, Qafzeh, and Skhul (~120,000 – 195,000). In fact the data from such finds, seen together with earlier finds from Africa (Jebel Irhoud, Herto, Omg Kidish, Florisbad) indicate that an “archaic” Homo sapiens sp. was possibly an expanding meta-population that extended its range over parts of Eurasia some three hundred thousand years BEFORE it was overtaken and absorbed by an even faster expansion of anatomically modern Homo sapiens sapiens. The dating for the two fragmentary Omo skulls – also thought to represent “archaic” Homo sapiens – has recently been revised in excess of 230,000 years.



Meanwhile, we have evidence that some of these archaic Homo sapiens also survived until recently, in Africa, as well. (see Harvati K, Stringer C, Grün R, Aubert M, Allsworth-Jones P, Folorunso CA (2011) The Later Stone Age Calvaria from Iwo Eleru, Nigeria: Morphology and Chronology. PLoS ONE 6(9): e24024. and the article by Vincent Plagnol , Jeffrey D Wall, Possible Ancestral Structure in Human Populations, in which they write: “While the putative source population may not be as obvious as in Europe (Neanderthals), the fossil record shows that transitional forms of Homo were widespread in Africa, even after the time of emergence of modern humans. Other genetic studies have also found evidence for ancient structure in African populations…”

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The discovery of a human jawbone at Misliya cave, on the western coast of Israel, dated as early as 194,000, was referenced in another report, from the University of Wisconsin, on research by paleo-climatologist Ian Orland, who explained that “The Eastern Mediterranean was a critical bottleneck for that route out of Africa and if our suggestion is right, at 125,000 years ago and potentially at other periods, there may have been more consistent rainfall on a year-round basis that might enhance the ability of humans to migrate.”


Map of the potential distribution of archaic hominins, including H. erectusH. floresiensisH. neanderthalenesis, Denisovans and archaic African hominins, in the Old World at the time of the evolution and dispersal of H. sapiens between approximately 300 and 60 thousand years ago. Credit: Roberts and Stewart. 2018. Defining the ‘generalist specialist’ niche for Pleistocene Homo sapiens. Nature Human Behaviour. 10.1038/s41562-018-0394-4
This map was presented in an on-line report released by the Max Plank last year



According to some models, this sets back the timing for the “out of Africa” movement of Homo sapiens sapiens, the anatomically “modern” people we represent today. Previously this was thought to have occurred around fifty thousand years ago, as illustrated by this map, adapted from “A climatic context for the out-of-Africa migration“, published October 2017, authored by Jessica E. Tierney, Peter B. Demenocal, and Paul Zander, in the journal of the Geological Society of America. (the authors have made this article available on Researchgate here.

Caption
Figure 1. Site map and schematic of geographic expansion of Homo sapiens from 200 ka to 50 ka. Data from this study are derived from marine sediment core RC09-166. Also shown are locations of the Ocean Drilling Program (ODP) Site 968 sapropel record and Soreq Cave (Israel)…
This figure was uploaded by Peter B. Demenocal

What happens to our models – if we consider all the descendants of Homo erectus – Neanderthal and all the others – as members of a widespread polytypic species: “archaic” Homo sapiens? During the climatic turmoil of the last two million years, it seems that some local populations of both the parent or ancestral species and the penultimate poly-typical representative, died out or got absorbed as a more successful variant arose. This happened several times, and seems to have involved a combination of a) gene flow, through the original meta-population, via extensive networking that linked neighbouring groups*, and b) population growth as a faster-reproducing variant expanded its range. Such range expansion is most likely to occur if there were biogeographic events that caused previous occupants to suffer inbreeding depression or be extirpated altogether.

The occupation of the planet was not a zero sum game where one sole winner emerged. It was a long precarious application of a novel adaptive strategy – one that shaped intergenerational transmission of behaviour largely through cultural patterns.. which demanded of every human individual increasing cognitive capacity to fit into, not just a cognitive niche, but a COLLECTIVE cognitive niche: this thing we often label “Culture”. 

We made it. The vast majority of infant Homo sapiens born on this planet today can learn any language; can learn to fit into any culture into which they are reared, even if it differs from the one where they were born. As a beautiful example of this, I submit the case of a young lad born in Columbia, adopted at three months into a Saami family: https://www.youtube.com/watch?reload=9&v=woEcdqqbEVg

In fact, even adults can continue to learn new languages and to learn the ropes of new cultures (otherwise participant observation in-depth anthropological ethnography would never have been possible).

After that, what does anything matter but that all through the Pleistocene we continued to evolve cognition/behaviour systems finely tuned to cooperative (shared and learned thus collective) cultural adaptations? 

Over and over again our species was hit with profound crises where our very survival was at stake, and we made it. We made it because we ultimately learned to be the gardeners of eden… we learned how to manage – to engineer – the ecosystems of our planet to preserve species diversity and water table stability everywhere – against formidable odds.  All modern hunter-gatherers do this: even in the arctic, they replant favoured wild species of vegetation, maintain very accurate assessments of wild game numbers and reproductive rates, and tend to prey switch when numbers are down. They also, both deliberately and through unconscious habit, create ecological hotspots of soil fertility and species diversity, simply by leaving behind campsite after campsite with deeply accumulated ashes, and midden and latrine areas.

During the several hundred thousand years we have labelled “the Middle Stone Age”, these changes happened in bits and pieces, appearing and disappearing: as scattered camping parties of high mobile hunter-gatherers met and exchanged ideas, technologies, stories, and occasional personnel, and as all sorts of memes, insights, stories, songs, dances. All innovations and ideas, like material objects could thus be wafted effortlessly via six or seven degrees of separation across linguistic and demographic overlaps to span an entire continents.

One more thing… as it all eventually came together, it was these ideas and practices were assembled into a hunter-gatherer culture, there was a shift that is visible in the archaeological record: technologies began to more frequently reflect “distance” hunting – using hafted technology like spears, spear throwers, bows and arrows, and also the plant and animal remains indicated prey switching and broadening of the subsistence base as well as of the ecosystems exploited in the course of a seasonal round. Seafoods were incorporated more frequently. All of this appears to have transformed selection pressures on the overall anatomy. 

Especially men, in the beginning, ceased be so often injured, maimed, and even killed when grappling at close quarters with large, frightened, and injured animals. Hunting from a safer distance and relative silence also changed the behaviour of game: flight distances reduced, as the animals did not necessarily connect the human glimpsed at a distance with the sudden start of the animal struck by a hurled spear. It was especially effective to hunt with small arrows, tipped with a slow acting poison, since the animal that was hit often merely started, trotted a short way, and then returned to grazing. 

This kind of hunting made a shift in selection possible: for the first time, selection that favoured energetic efficiency over brawn and thick bones. Small lean hunters could return more calories relative to what they spent on a hunt, allowing more calories for growing children, smaller women could gather more efficiently for the same reason, and also spare more calories for their growing fetuses, and producing more milk for babies. Pregnancies, one might ask, could possibly have more often ended successfully, fewer children would have experienced seasonal hunger, and fewer men would have had to spend weeks recovering from concussions or broken limbs.

With this more level play field, the genetic odds tipped toward what we now call the “anatomically modern” human.

As these gains let our ancestors increase their numbers and expand their range, I wonder if our view today is biased toward seeing competition and even occasional genocide as somehow the most plausible way our ancestors dealt with all the other little struggling groups of humans they found? 

I have come to question this. The genetic proof of a period of widespread hanky-panky is pretty clear. 

And when that last mega-drought ended in Africa around 74,000 years ago, and as the population doubled and doubled and doubled – something I estimate would have taken about a millennium and a half, each time… and again occupied parts of the Near East, most people would hardly be aware of having entered another continent…They were, perhaps, reoccupying places spoken of in stories about distant relatives – the ones who lived for a time at Misliya, perhaps, handed down for 40,000 years.

When any living descendants of these distant and mythological people occasionally appeared, there were literally centuries for each group to become acquainted with the other’s language and customs, to negotiate access to fishing, hunting, and gathering opportunities, and to negotiate peace if misunderstandings and fighting broke out. 

The planet-encompassing scope of that last expansion was something no one could have any concept of, at the time. But it can be mathematically modelled, and if you do that based on even the modest rates of population growth typical of modern hunter-gatherers, it did not take more than twenty or thirty thousand years for these anatomically modern humans to number in the several millions in Eurasia alone.

Given that, it is not at all surprising to me that some might have made it to the islands of the Sahul within that time span. They were not, after all, the first people there. As for Australia, I have to say, I would not be surprised if evidence of “archaic” Homo sapiens, (followed of course by more and more “modern” Homo sapiens, eventually is found there. it would not be a shocker: that is what happened everywhere else but in (as far as we know) the Americas. 

What of those scattered groups of archaics – the Neanderthals, Denisovens, and Anatomically Archaic Africans – what did they experience? I would like to think they were more curious and interested than threatened and indifferent; I would like to think they had already learned the hard way that too much isolation and inbreeding led to bad outcomes; I would like to think we “anatomically modern” humans looked perhaps a little weird to them, as they might have appeared to “us”, but recognizably human and, potentially, as allies and friends.

Perhaps, too, they saw in us an opportunity for novelty and even, for rescue from isolation. I do think we brought them into “our” human family, as much as they welcomed us into theirs, and it is thus, all OURS now. So I doubt was a simple or one-sided process. In Africa, and in the rest of Eurasia, there were both genetic and cultural elements gained as a result of these meetings, this blending… of technology, of knowledge, and of a future. But we owe much of our present form, genetics, and certainly most of our present languages, to that last wave. And the evidence is strong that that last wave began along the coasts of SE Africa.


This image is from a 2015 online post at
https://www.past.org.za/looks-aside-dna-shows-99-9-alike/
Looks aside DNA shows we¹re all 99.9% alike. Fossil and genetic evidence supports this completely, confirming that Africa is humankind¹s birthplace, but that ancient changes in environments ­ from cold and rainy to sunny and dry ­ shaped human development over the eons. Thus our differences in skin and facial features explains Prof Robert Blumenschine… who reported on the following article https://www.iol.co.za/dailynews/lifestyle/looks-aside-dna-shows-were-999-alike-1952592#.VlxCyv2hfIU



Even more interesting, of course, is the evidence of the survival of small and relatively isolated populations of smaller brained Homo sp. populations from previous range expansions (Homo habilis? early Homo erectus?).

Let us be clear: the existence of Homo naledi, Homo floresiensis, and others like this, even until fairly late in the fossil record, is not an unusual pattern in mammalian biogeography. It is like the survival of pockets of many other “earlier” widespread polytypic species that subsequently disappeared in much of its former range, like the Pronghorn antelope, or the late much lamented Sumatran Rhino.

What these finds do, however, is disabuse us of the notion that early species and subspecies of Homo were not as “successful” as the later ones, like ourselves. It wakes us up to the reality that teleological assumptions about our own prominence in the natural world was somehow inevitable, let alone that it will necessarily persist and let us expand to the rest of the solar system.

At least, that is my hope: please let us have learned enough to tap hubris on the head, take its hand, and lead it away from the present precipice.



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