There is scarcely a week that passes that we do not hear of a new discovery in anthropology that further opens up the deep human past to scientific inquiry. Most recently, it has been reported that Homo sapiens regularly interbred with other related but distinct hominids (cf., e.g., Ancient Denisovan DNA excavated in modern Pacific Islanders). The flood of scientific evidence about our own past is in part a result of the anthropic bias that drives us to focus on our own natural history to a greater degree than the natural history of other species, but in this case anthropic bias has had a paradoxical outcome: we have experienced a Copernican revolution in our self-understanding as a species. The once-controversial idea that many distinct hominid species co-existed in relatively recent prehistory is now widely accepted, which places our former assumptions about human uniqueness in question.
A new wrinkle in early human history has been introduced by the discovery in China of anatomically modern human teeth dated to between 80,000 and 100,000 years before present (cf. Teeth from China reveal early human trek out of Africa and Ancient teeth found in China reveal early human migration out of Africa). This discovery was widely reported in the science press in October 2015. We should not be surprised by this discovery, as pre-human ancestors had already made their way out of Africa; when Homo sapiens began its dispersion into Eurasia, Eurasia was already populated by hominids who had earlier left Africa, and it is likely that Neanderthals were a species of hominid (or a subspecies of hominid) that separately evolved in the Levant or Europe from earlier (and distinct) hominid ancestors that came from Africa.
In anthropology, the idea that distinctively modern human beings (i.e., anatomically modern Homo sapiens) originated in Africa and then spread outward from there is called the out-of-Africa hypothesis (also known as OOA). Another idea is called the multiregional hypothesis, according to which human beings first spread out across the Earth, and then separately but nearly simultaneously achieved their modern form in multiple geographically distinct regions of the world. Multiregionalism as a scientific theory in anthropology has been somewhat like the steady-state cosmological theory of Fred Hoyle, Hermann Bondi, and Thomas Gold: it has provided some interesting scientific insights, but it fails to accord with evidence when it comes to the ultimate framework for scientific thought. (I recently learned that Robert G. Bednarik defends the multiregional hypothesis. I’ve been skimming his book, The Human Condition, and while I am sympathetic to his criticism of the “African Eve” narrative, this is not at all essential to an account of cognitive modernity, nor would a rejection of “African Eve” necessarily entail multiregionalism.)
Darwin himself addressed multiregionalism long before the idea had this name:
“Although the existing races of man differ in many respects, as in colour, hair, shape of skull, proportions of the body, etc., yet if their whole structure be taken into consideration they are found to resemble each other closely in a multitude of points. Many of these are of so unimportant or of so singular a nature, that it is extremely improbable that they should have been independently acquired by aboriginally distinct species or races.” (Charles Darwin, The Descent of Man, Part I, Chap. VII)
There is, of course, convergent evolution, but convergent evolution does not arrive at the identically same species, but species with a similar appearance due to a response to similar selection pressures: this is why marine mammals like whales and dolphins look vaguely like fish, even though they aren’t fish.
For the multiregional hypothesis to be true, the genetically identical species of homo sapiens would have to separately and independently evolve in geographically isolated regions. Given that human beings are, genetically speaking, more closely related to each other than the members of many other species are related to each other (although cheetahs, for example, are even more closely related than human beings, pointing to an even more recent and severe bottleneck in the species’ history), this greatly raises the bar for the multiregional hypothesis.
It is not enough to identify multiple hominid species as being the same species either by applying the honorific “human” to all of them, or by demonstrating (which we cannot now do after the fact) that individuals of diverse lineages and from separate populations can mate and produce fertile offspring. If someone is going to maintain multiregionalism, then the nearly identical human genome of today, in its widely geographically separated instances, had to have converged upon an identical sequence by different means.
Evolution never works in this way. The most commonly cited process of speciation is allopatric speciation, which involves the geographical isolation of two populations originally the same species, but which in geographical isolation genetically diverge under distinct selection pressures. Peripatric, parapatric, and sympatric speciation are also possible, but probably are less frequent mechanisms for speciation because of the absence of a geographical barrier to gene flow. The structure of Earth itself has facilitated this process (processes that I call speciation pumps.). Macroevolutionary biological changes have been driven in the past by macroevolutionary geomorphology, i.e., plate tectonics, which has repeatedly separated populations and then joined them together again over hundreds of millions of years. (Macroevolutionary climatological changes have also played a significant role in driving speciation.)
Now, after this rather strongly formulated rejection of multiregionalism, I will perhaps surprise the reader by asserting that there is another possible form of multiregionalism that may well be the case: not a biological multiregionalism of the miraculous appearance of the same genome by different processes in different parts of the world, but a cognitive multiregionalism, with cognitive modernity separately emerging in different geographical regions from the anatomically identical modern human brain of homo sapiens, which anatomically modern brain was in turn an expression of the modern human genome. Anatomically modern homo sapiens may have dispersed throughout Eurasia and only then, in widely disparate geographical regions of Earth, attained cognitive modernity separately and independently.
The cognitive development of a distinct population within a single species is tied to biology, but not exhaustively determined by biology. Cognitive evolution is distinct from biological evolution, which we must keep in mind not only in researching the distant human past, but also in the distant future (or the analogue of our future realized in some other more advanced species): despite our increasing ability to quantify the earlier terms of the Drake equation, for example, none of this helps us at all to quantify the later terms of the Drake equation, which all concern cognitive evolution, or what is sometimes called social evolution. The two — biological and cognitive evolution — are distinct, although not absolutely so.
With anatomically modern human beings in China as early as a hundred thousand years ago (i.e., not long after the appearance of Homo sapiens as a distinct species), it seems that one can maintain one of the following theses on cognitive modernity:
- There is no cognitive modernity as distinct from anatomical modernity (this is David Christian’s position, as far as I understand it)
- Cognitive modernity occurred prior to 80,000–100,000 years before present (which is significantly earlier than dates usually placed on cognitive modernity), or
- Cognitive modernity followed a multi-regional model.
Since I would argue for cognitive modernity as distinct from anatomical modernity, I would exclude the first of these three, and I would hesitate over the second. The Mt. Toba catastrophe theory has been closed tied to theories of cognitive modernity (there is no current consensus on the theory, and it has been dismissed by many anthropologists), and the Mt. Toba eruption dates to about 70,000 years before present, so that any selective population bottleneck as a result of the catastrophe would have had to come after that. This is sufficiently long of a period of time after the date of the teeth discovered in China that no cognitive modernity in Africa 70,000 years ago could account for cognitive modernity in human beings separately arrived in China more than 80,000 years ago.
These considerations, among others, have pushed me to consider the possibility of multiregional cognitive modernity. This idea is not perfect, as cognitive modernity was one of the factors that allowed human beings to establish themselves throughout the world, using their advanced skills and technology to make their way through the glaciated world of the Upper Paleolithic. But even Neanderthals had rudimentary clothing, though they did not sew the form-fitting clothing that modern humans crafted with the use of bone needles. Was this lower level of technology sufficient to account for anatomically modern, but not cognitively modern, human beings to make their way from Africa to China?
Some general observations about the possibility of cognitive multiregionalism follow:
First Observation: Cognitive modernity need not be a black-or-white, discrete event in time; cognitive modernity may be a spectrum and may have emerged over time. This observation could be highly controversial, as it suggests the possibility of different human populations achieving cognitive modernity at different times (and under different circumstances). This, in turn, would be an affront to Enlightenment universalism and its postulation of a single (or no) human nature.
Second Observation: If, as I argued in a recent post, encephalization is the Great Filter, then the developmental events after encephalization — which for me would include cognitive modernity — would not present the same degree of unlikelihood as separate instances of encephalization. Cognitive modernity might, then, be achieved without the great difficulty of overcoming a major developmental barrier.
Third Observation: Cognitive multiregionalism could be used to explain the differences among civilizations separately emergent in different parts of the world. If the emergence of civilization, like encephalization, is not the great filter, and does not present the fundamental barrier to the proliferation of intelligent life, then we would expect that civilization, like cognitive modernity, would naturally emerge at many times and places as soon as the opportunity arises — and this is exactly what we find in the historical record.
While cognitive multiregionalism has obvious vulnerabilities, I think it is an idea worthy of further development and could be formulated so as to offer an explanation for many currently problematic episodes in early human history. And I am not blind to the many controversies that would follow from adopting multiregional cognitive modernity as a research program.