Friday, February 6, 2015

On semi-hidden agendas and the misuse of Gödel's theorems

An old friend of mine, a philosophy PhD with a background in literature and theology, told me that it was the work of Kurt Gödel which had drawn her to philosophy. She, like many others (including myself at one stage), saw his famous theorems as vindicating a non-reductionist and perhaps even religious view of the world.

I don't think this view is correct. A mythic narrative has been built up around Gödel's work which needs to be treated with great skepticism. Certainly his work could be seen to have decisively undermined one aspect of the so-called Hilbert program, but what reason was there to think it likely that a formalized version of arithmetic could be complete or have the necessary resources to prove itself consistent in the first place? And why does this matter so much anyway (except perhaps to mathematicians who might have been seeking a certain kind of certainty or security or self-containedness for (fundamental parts of) their discipline)?

I concede that there are many deep and interesting questions which work by Gödel and others (Turing, Church, Post, et al.) opens up in metamathematics, computer science and other areas. But I question its relevance (or at least its direct applicability) to general human questions.

I say these things to give a sense of my general stance and it is not my intention here to elaborate or defend a comprehensive point of view. Rather, I just want to sketch out my reaction to some posts at Scientia Salon by Marko Vojinovic whose PhD is in theoretical physics but whose interests appear to be largely philosophical. In January a two-part essay of his appeared which uses Gödel's work in what I see as an inappropriate way. [Part I here and Part II here].

Initially I was going to write a more harshly anti-Vojinovic piece but, rereading the pieces and some comments and responses I have tempered my original views somewhat. On a personal level, I think I would like Vojinovic. He writes well and engages readily with his critics, often in a disarming way. He is clearly intelligent and knowledgeable and interested in interesting things.

Nonetheless it remains crystal clear that he has a (not particularly hidden) agenda. In fact his contributions to SciSal (including comments on posts by others) could be seen to provide (further) evidence in support of points I have made in the past about (sometimes hidden) ideological or religious agendas lying behind much philosophical discourse.

The basic pattern is a common one. One has a fundamental view of how things are which one has arrived at for unknown, obscure or unknowable reasons, and one deploys one's intellect and knowledge of science, maths, logic, etc. (i.e. one's expertise) to make a case for or defend the plausibility of one's intuitively held views.

On one level, this sounds fine. And it is fine. Conjectures and refutations. Popper et al.. We can't escape it. Much of science and philosophy and ordinary argument is like this, and that's okay.

But there's a continuum involved (or a multitude of personal continua). My point is that if religion and maybe some other kinds of ideological commitment are too strongly involved the whole process becomes problematic.

Certain aspects of my own personal history give me an insight into these issues. I used to be religious and, just like Duhem (a classic case if ever there was one), I felt that I had an epistemic head start on others because I knew that the true theories of science etc. had to be compatible with my beliefs and, plainly, many popular theories and interpretations were not. Moreover, I was strongly motivated to argue my case (for obvious reasons). I even saw a career in academia (in philosophy, for example) as a possible way of promoting these ideas (and doing good, because the ideas were good and true).

When you are getting too close to the apologetics end of the continuum, expertise is deployed merely to serve the argument. And, as every high-school debater knows, any intelligent person can make a plausible-seeming case for any half-plausible proposition. In the light of these facts and, given the overwhelming amount of stuff out there which might call for our attention, lines just have to be drawn.

It's a personal thing, where one draws the line. I would exclude Pierre Duhem but include Popper (say) – despite the latter's belief in an essential truth underlying religion and his commitment to (something very like) Cartesian dualism – in my personal list of thinkers worth reading for not purely historical reasons.

So where does Marko Vojinovic's work lie on this continuum which runs from careful, exploratory argument to polemics and apologetics? His writing (at least at Scientia Salon) tends to the latter end of the spectrum, I would say. The essays are certainly tendentious.

In a September article at SciSal, he argued against determinism but his argument relied on so many contested assumptions that, even if his reasoning was valid, the soundness of the argument was far from assured. Vojinovic also claimed somewhat surprisingly – and very revealingly – that his conclusions "open[ed] the door for the compatibility between the laws of physics on one side, and a whole plethora of concepts like free will, strong emergence, qualia, even religion – on the other. But these are all topics for some other articles..."

Then, early in January, the two-part essay on reductionism and emergence appeared, with even more extravagant claims in the final paragraph, claims which one sympathetic commenter interpreted as "a tactical error".

Here is the final paragraph in its entirety:

"Giving up the idea of reductionism essentially amounts to accepting strong emergence as a fundamental property of Nature — a physical system might display behavior that is more than the behavior of the sum of its parts. Proponents of reductionism might find this at odds with their favorite ideology (physicalism, naturalism, atheism, etc.), but there are actual examples of strong emergence in Nature, the arrow of time being the most prominent one. It would be interesting to see how many people would actually agree to change their minds when faced with this kind of approach, as giving up reductionism generally weakens the arguments that a physicalist may have against dualism, a naturalist against the supernatural, an atheist against religion, etc. Philosophy teaches one to keep an open mind, while science teaches one to appreciate the seriousness of experimental evidence. When these two combine to demonstrate that certain parts of a physicalist/naturalist/atheist belief system are just unfounded prejudices, even downright wrong, it would be interesting to see how many people will actually give them up. After all, these are precisely the people who boast about both open-mindedness and the scientific method, and invoke them to criticize dualists/supernaturalists/theists. Now they are challenged with giving up one of their cherished beliefs, and I would like to see how truly open-minded and scientific they can be in such a situation."

Overall it seems clear that Vojinovic's philosophico-religious preoccupations have led him to deploy some very idiosyncratic definitions of key words and to make false (or at least very misleading) claims, claims which he has sometimes backed away from when challenged in the comments section – like the claim that his concerns were ontological rather than merely epistemic. (How can Gödel's work be used to make ontological claims if it is all about what we can know and what we can prove within the context of a formal system?)

I agree with those who call into question Vojinovic's use of Gödel's work (and in general the appropriateness of applying Gödel's ideas to scientific theories) and who talk about the red herrings, etc. which the author's use of Gödel has generated.* Gödel's results are specifically about what we can know and prove within certain strictly formal contexts, i.e. it's not about normal scientific thinking. You can axiomatise certain theories, sure, but such formal structures are entirely provisional from a scientific point of view and subservient in the end to empirical considerations.

In his enthusiasm to make his case, Vojinovic even appears to misrepresent Gödel's basic claims. He writes in a comment: "The moral of the [sic] Gödel’s theorem is that there is a difference between truth and provability, in a given axiomatic system. … Gödel’s theorem establishes the existence of statements that are (a) unprovable within a given axiomatic system, and (b) also “true” in that axiomatic system, given any notion of truth the axiomatic system may be compatible with."

"No," replies one commenter, "there is only one notion of truth in an axiomatic system. That is, provability from the axioms. Yes, there are unprovable statements in ZF [Zermelo-Fraenkel set theory (in effect, first-order logic enhanced to encompass arithmetic: Gödel's original paper referred to Russell and Whitehead's system)]. Such a statement will be either undecidable or provably false. An undecidable statement is true in some models of ZF, and false in others. Gödel proved the existence of undecidable statements in ZF, assuming consistency of ZF. Those statements have a metaphysical interpretation in which they are true, but they are certainly not true in ZF, as Gödel proved that there are models of ZF in which they are false."

Conclusion: "Almost everything Marko says about Gödel is wrong."

Hyperbole perhaps. But the main point is that Vojinovic overreaches by trying to apply Gödel's findings to a hypothetical axiomatised 'final theory'. Science is never about certainty in the way logic or pure mathematics is about certainty – and doesn't aspire to this kind of certainly. This simple fact, I think, undercuts Vojinovic's whole argument.

Sure, the validity of arguments on scientific questions matters, but the primary focus is not on validity (as it is in logic, etc.) but on soundness. The axioms, in other words, must all be 'true' – and this is something we can never affirm with absolute confidence. They are always going to be provisional and revisable (in the face of new evidence); and the formal system or theoretical context in which they are embedded is likewise always going to be provisional, even if it functions successfully as – and so is thought to represent – a 'final theory'.

* "... Marko wants to prove that Weinberg’s reductionism is wrong. There are several problems. If Goldbach’s conjecture turns out to be undecidable, then why would that have any physical implications? And if it did, then some physical experiment ought to decide it, thereby eliminating the issue as any impediment to reductionism. So there is no actual connection between Gödel and reductionism, except to confuse readers with red herrings." [From Part II comment thread.]

Monday, December 15, 2014

Mathematics; panpsychism

Last month I listed a number of topics (mainly linguistic, psychological and historical) I have been thinking about. The last item on the list was the most philosophical, relating to the challenge that mathematics can be seen to pose for empiricism.

Mathematics is often presented as a deep and interesting area of knowledge which is somehow independent of the empirical world. Well, it certainly is a deep and interesting area of knowledge, but it is also very much a product of physical brains interacting with the wider physical (and cultural) world. Sure, it operates at a very high level of abstraction; and, sure, many mathematicians are mathematical realists (or Platonists) who feel themselves to be exploring (and discovering things within the context of) an independently-existing and non-empirical realm.

But the old idea of a realm of pure mathematics without applications (promoted by mathematical Platonists such as G.H. Hardy) is looking increasingly forced and dated (i.e. tied to a particular cultural tradition). It's well known that ideas from pure mathematics often find subsequent – and unexpected – applications. Non-Euclidean geometries, for example, were originally developed in the 19th century as pure mathematics but subsequently found applications in cosmological theories.

What Hardy shied away from particularly, however, were technological applications. He would not have been happy that his own area, number theory, which he loved for its purity and uselessness, turned out to have important applications in computer science.

Cantor, of course, was also a Platonist. I was looking again at his 'diagonal argument' which shows that the set of real numbers is not countable (denumerable) – so that some infinite sets (as George Orwell might have put it) are more infinite than others.

But I always feel uneasy when infinities (even common or garden variety infinities like the sequence of natural numbers or the expansion of pi) are built into arguments. Cantor's argument is clever and convincing in a sense, but the (infinite) matrix on which it is based is merely imagined (or postulated, or projected).

I think I'm okay with mathematical procedures which involve an unending series of steps (potential infinity); but not with mathematical objects which contain an infinite number of elements (actual infinity).

So it seems that I am an intuitionist, but I can't really say at this stage whether I'm a finitist also. (The latter only recognize mathematical objects which can be constructed from the natural numbers in a finite number of steps).

Another topic I've been thinking about is panpsychism. What prompted my (renewed) interest was coming across a philosophically-oriented blogger with a PhD in theoretical physics whose nom de plume happens to be 'Panpsychist'. He had made some intriguing comments on a post by Massimo Pigliucci on reductionism in science and invited people to continue the discussion on his site. (Massimo has set limits on comments at Scientia Salon.)

I followed quite closely but didn't participate in the reductionism debate which was characterized by a certain degree of terminological confusion, specifically about the meaning and application of certain terms used in the philosophical literature, e.g. "token physicalism" (which is associated with "supervenience") and "type physicalism" (which is associated with "strong emergence").

Panpsychism is relevant to the topic of reductionism in that it can be seen as a way of getting around the problem of reducing mental properties to physical properties.

'Panpsychist' rejects dualism and also rejects the idea of emergence, the idea, as he puts it, "that mental properties emerge from certain configurations of regular, non-mental matter." He says that reading David Chalmers convinced him that the standard idea of emergence was wrong because it failed to address the 'hard problem' of consciousness. He also argues against the view that panpsychism is an essentially religious position.

Some time ago I considered and rejected David Chalmers' take on the so-called hard problem of consciousness as unconvincing and unscientific. Basic to his approach is imagining beings that look and behave just like humans but lack conscious awareness; logically coherent perhaps but utterly implausible both in terms of common sense and in terms of science.* Biological creatures have various levels or degrees of consciousness or awareness or sentience: that's just how things work. And imagining a world in which quite arbitrary – not driven by scientifically-based reasoning – differences apply is merely idle speculation. Also, Chalmers-inspired approaches tend (as I see it) to be too much focused on human consciousness rather than on more primitive – and basic – forms of awareness from which the former ultimately derives. The sentience of simple life-forms is where the real (philosophical) interest lies, in my opinion.

I have also in the past seriously considered and rejected panpsychism, but I do acknowledge that the curious spectacle of an apparently inanimate universe producing sentient and ultimately conscious organisms – and so in a sense becoming conscious of itself – does give one reason to ponder the possibility that consciousness (in some form or other) is fundamental (in some sense or other).

Looking again at these issues, I note that the revival in panpsychism in philosophical circles (prompted in part by Chalmers' work in the 1990s) is being driven largely by 'process' thinkers. (It used to be called 'process theology' but the 'theology' is generally dropped these days and replaced with 'thought' or 'thinkers' or nothing at all.) It all goes back to Whitehead – and ultimately to neo-Platonism, I suppose.

I tried to read Whitehead a couple of times, but found him rather vague and wordy and (unnecessarily?) obscure. It's not just that he had grown up when 19th-century philosophical idealism was at its zenith and had internalized old idealist assumptions and ways of speaking because I've read and found interesting the work of F.H. Bradley who was not only an idealist but had far less mathematical and scientific knowledge than Whitehead. I think perhaps Bradley had keener insights into human psychology than Whitehead and so was more grounded. He also had a better prose style, which is often a sign of groundedness.**

Despite not warming to Whitehead's work (or that of his followers), I do like the idea of seeing fundamental reality as process rather than 'stuff'. (The fact that matter and energy are functions of one another makes old-fashioned materialism unviable.)

This view fits in nicely with the idea of computation, and with seeing the cosmos as some kind of computational (or computation-like) process.

And finally, returning to mathematics, I see the natural numbers also in terms of process: namely iteration.***

* As I see it, logic derives from and is intimately related to mundane real-world and scientific reasoning. Logic may be an independent discipline but this does not entail that the subject of the discipline constitutes or forms the basis of some kind of alternative reality.

** Heidegger comes to mind here also: despite the excesses and idiosyncrasies, his language meshes with reality somehow (at least some of the time!).

*** As they are expressed, for example, in Church's lambda calculus. On the whole, Church is a bit too abstract (and Platonic) for me however.

Sunday, November 2, 2014

Thoughts and questions

Here are some thoughts and questions which have come to mind recently. I will definitely be following up on some of them.

• Human communication is not what it seems. This is a fact which typically takes some time (and multiple relationship failures) for us to learn. Even relatively straightforward and sincere messages are routinely construed by recipients quite differently from how senders conceive them such that, while what is being sent and received at the level of symbols is the same thing (i.e. the same set of symbols), what is being sent and received at the level of interpreted symbols are different things.

• The contingent (and unrepeatable) features of any individual's upbringing – which includes as a central element a unique and ever-changing cultural matrix – raises awkward questions about values. We like to think of our core values as being, if not objective or universal, then at least as having some permanent or abiding relevance. But do they?

• Terms like 'moral' and 'ethical' refer to important aspects of human behaviour but I am inclined to think that ethics can only be usefully intellectualized when approached in a more or less descriptive way. Nietzsche in his more scientific moods is my model on this front. I don't know that normative ethics can ever be a coherent intellectual discipline – in part because making moral judgments and decisions is not just an intellectual matter. A very 'thin' kind of ethics based on notions such as reciprocity might be seen as a precondition for any kind of social life and so as uncontroversial, however.

• Is there – as Karl Kraus thought – a deep and intimate link between morality and how we use language? (I don't think so. Not in the way Kraus saw the matter, anyway.)

• What is the cause (and significance?) of the disappearance of the subjunctive and, more generally, of formal and literary modes of speaking and writing?

• What is the source and significance of that strange sense of dread and guilt which some people feel deeply and others don't feel at all? This is one of those many topics which you could approach via psychology or historically. The Etruscans were said to be particularly prone to such feelings, and certain strands of Christian thinking were driven by this sort of thing. There was, I recall, an obscure member of the Vienna Circle who wrote something on this topic (taking a psychological approach). Must look him up.

• The Idealist and Romantic notion of the spirit or genius of a language or a people generally makes far too much of linguistic and cultural groupings, imputing to them not only a life of their own but also a destiny to fulfil, a totally implausible – and very dangerous – idea which is still being energetically propagated today. Culture is crucially important, but clearcut cultural and linguistic boundaries between languages and cultures simply don't exist.

• In fact, the very notion of a (natural) language is problematic. Certainly it represents an abstraction from empirical reality. (Chomsky believes that there are only (overlapping) idiolects.)

• The early-20th century fad for constructed international languages: what was driving it? How did this movement – or competing set of movements – relate to other international movements of the time, like socialism for instance?

• The nature of mathematics. Can mathematics be fitted into a (broadly) empiricist epistemology and/or a naturalistic worldview?

Monday, September 29, 2014

Dial M for Metaphysics

I had to laugh when I saw this advertisement for a kind of New Age one stop shop. You can certainly imagine people paying these folks to get hypnotic help to give up smoking or lose weight, or access other services like counselling or massage or even astrological guidance. But I just couldn't figure out why anyone would want to consult a metaphysician.

Of course, what these people mean by 'metaphysics' is very different from what academic philosophers mean by it. The term has long been appropriated by New Age types. What you might find in the metaphysics section of a bookshop, for example, would bear no relation to what academic philosophers mean by the term.

In fact, the very word 'philosophy' is becoming problematic. People have all sorts of notions of what philosophy might be, but few of them mesh with how academic philosophers see their discipline. And even academic views of philosophy tend to diverge alarmingly between different schools of thought and traditions and even between individuals.

I recently tweeted [@englmark] the above photo with a comment to the effect that the appropriation of such words by others may indicate that academic philosophy is losing the battle for the very terms which have traditionally defined it. This prompted the philosopher Massimo Pigliucci to come in and suggest that science and the sciences face similar problems. He cited so-called 'creation science' and the use (or misuse) by mystics of quantum physics.

But neither example is a complete appropriation and both merely represent attempts to use the prestige and respectability of science to promote religiously-driven points of view.

Unlike Massimo, I think that confusion over terms like 'metaphysics' and 'philosophy' may be indicative of more general problems facing the discipline, and that academic philosophy has suffered a significant loss of status in recent decades – especially in scientific and secular circles. (An essay of mine published earlier this month at Scientia Salon dealt with some of these issues.)

Saturday, August 16, 2014

Designing a conscience for warrior robots

You wouldn't normally expect to come across a reference to deontic logic in a Bloomberg opinion piece but a recent article on the perceived dangers and possible downside of artificial intelligence cites a paper [PDF] which, drawing on formal logical and ethical theory, proposes a method for creating an 'artificial conscience' for a military-oriented robotic agent.

The paper, by Ronald C. Arkin, "provides representational and design recommendations for the implementation of an ethical control and reasoning system potentially suitable for constraining lethal actions in an autonomous robotic system so that they fall within the bounds prescribed by the Laws of War and Rules of Engagement." *

What interested me particularly was seeing basic logical and ethical theory being seriously discussed and applied in such a context.

Arkin sees virtue-based approaches as not being suitable for his purposes because they are heavily reliant on interpretation and on cultural factors and so are not amenable to formalization. Utilitarian approaches may be amenable to formalization but, because they are not geared to utilize the concept of human rights, do not easily accommodate the sorts of values and outcomes upon which the research is particularly focussed (e.g. protecting civilians or not using particular types of weapon).

So Arkin opts for a basically deontological approach, but a scaled-down version which does not purport to derive its rules or guidelines from first principles or from a universal principle like Kant's Categorical Imperative.

Arkin's recommended design would incorporate and implement sets of specific rules based on the just war tradition and various generally accepted legal and moral conventions and codes of behavior pertaining to warfare.

He points out that machines programmed on such a basis would be likely to be more reliably moral than human agents partly because they would be unemotional, lacking, for example, the strong sense of self-preservation which can sometimes trigger the use of disproportionate force in human agents.

The main problem as I see it is that, in general terms, the more morally constrained the robot is, the less effective it will be purely as a fighting machine and so there will be an ever-present temptation on the part of those who are deploying such machines to scale back – or entirely eliminate – the artificial conscience.

Although the need to maintain the support of a public very sensitive to moral issues relating to such matters as torture and the safety of non-combatants would lesson such temptations for the U.S. military and its traditional allies, it would be foolish to imagine that other players and forces less committed to applying ethical principles to the conduct of war would not get access to these technologies also.

* Arkin is based at Georgia Tech, and the research is funded by the U.S. Army Research Office.

Tuesday, July 22, 2014

Faint possibilities

I have identified a possible flaw in a thought-experiment-based argument I posted here ('Kirk dies') some time ago. I wrote:

"We willingly go to sleep at night. We willingly get anesthetized for an operation. We might also be happy to go into 'cold storage' for a long space journey or to survive a devastating catastrophe on earth (a 'nuclear winter', for example).

But, what if, though we could be certain the hibernation device would not fail to keep our body alive and in a resuscitatable state, we just did not know whether or not it would ever get around to waking us up?

Going into such a device becomes exactly equivalent to a game of Russian roulette. Death (as in the death of the body) is functionally equivalent to not waking up, ever. All the death of the body does is make it impossible ever to wake up. It takes away hope.

But, from the point of view of the unconscious person, hope – or any kind of expectation – is irrelevant. So the experience of death is equivalent to the experience of going into a state of unconsciousness – nothing more."

The problem (as I now see it) is that I was overlooking the fact that a body which is revivable must, like any living thing, be in some sense sentient.*

A person requires consciousness as well as a social context, etc., and so is much more than a sentient body or body components. But the latter is the basis and sine qua non of the former and – crucially – is what makes me me and not you.**

The higher functions of my brain (or my 'mind') fade in and out, and may go permanently before my body fails. Once they are gone, I (as a functioning person) am gone. But in another sense I live on in my separateness until the death of the body.

In a fundamental sense, basic sentience is a far more interesting phenomenon than consciousness or self-consciousness, as it is the root of the latter. If there is a deep mystery in the universe, sentience is it. The primitive organism in a rock pool attracted to the warmth of the sun: this is what is most remarkable.

A human body, then, in some imagined technology-induced kind of super-hibernation would be unconscious but sentient (probably in many ways). And such a 'sleep' – even if extended indefinitely – is not at all equivalent to death.

I thought I had demonstrated (assuming that a functioning human body is entirely physical, i.e. soulless) that there can be no afterlife, no waking up (as it were) after death.*** But my little thought experiment was, I think, fatally flawed.

All sorts of possibilities – especially in an infinite universe (or multiverse) with multiple copies and so on – remain in place (faint though these possibilities may be).

* I am assuming here that any process which completely shuts down the functioning of organs, cells etc. would not be reversible: it would in effect kill the body.

** I know there are difficult questions about what it is exactly that confers identity on an individual or what identity consists of or in which I'm skirting here, but (if one rejects a Cartesian view) the living body is clearly basic.

*** Looking at things from a first-person perspective helps to keep these sorts of discussions grounded. Look, for example, at the sort of question that a dying person might ask him/herself. Something like: "Is this the end, the end of all experience (for me)?" I put the 'for me' in brackets because the burden of the question lies elsewhere. The dying person is not interested in me-ness but in whether or not there are going to be any more experiences. One can imagine – looking forward – waking up as oneself at another (say, earlier) stage of life, as someone else entirely or even as a giant cockroach – and I think these imaginings are at least coherent. (Kafka's giant bug had psychological continuity with the man who suffered the transformation. My cockroach doesn't (necessarily), and nor does my someone else. Thus the inserted clause, 'looking forward'.)

Tuesday, June 17, 2014

On modern human origins and the emergence of complex language

Though much about the movements, migrations, interactions and material culture of early modern humans remains uncertain, rapid progress is being made by researchers. Questions concerning the non-material culture of our ancient ancestors, however – and, in particular, concerning their languages or modes of language-like communication – are far more problematic. What follows are a few reflections on what, in general terms, we know, and what the prospects might be for learning more.

Our ultimate African origins are not in dispute, but there are still fundamental disagreements between supporters of models which see modern humans as having migrated (more or less recently) to other continents, replacing other hominins in the process, and supporters of versions of a multiregional hypothesis who see the evolution of modern humans from earlier forms not just as an African but as a worldwide phenomenon involving significant interbreeding between different kinds of hominin, complex gene-flows and a number of regional continuities dating back at least 200,000 years.

Despite these disagreements it is, I think, becoming increasingly clear that the recent African origin model, the view that modern humans arose as a new species in Africa and migrated to other continents around 60,000 years ago, replacing existing human species in the process, is at best an oversimplification. For there is now firm genetic evidence that interbreeding occurred between modern humans and Neanderthals in Europe and between modern humans and Denisovans in Asia, as well as evidence that migrations of modern humans occurred more than 100,000 years ago. New versions of the 'out of Africa' model – which push back the dates of migrations and take into account interbreeding between different human groups – bring it closer to a multiregional model, though any consensus is still a long way off.

A recent University of Tübingen research project exemplifies how the African origin model is changing. The study focuses on modern humans who migrated east via the Arabian peninsula area where stone tools dating from more than 120,000 years ago have been found. Two significant migrations – a very early one (ca. 130,000 years ago) along the southern coast of the Arabian peninsula and a much later one via a northern route – were hypothesized, and the researchers' models predict in general terms the actual data (skull measurements and genetic data) of population groups currently living in the Asia-Pacific region.

According to Hugo Reyes-Centeno, a leading member of the Tübingen team, Aboriginal Australians, Papuans and Melanesians were "relatively isolated after dispersal along the southern route" and other Asian populations were largely descended from groups migrating much later (about 50,000 years ago) along other routes, the main one going via the north of the Arabian peninsula and northern Eurasia.

These results need to be treated with caution, however, as the data on which the models are based are necessarily extremely limited and incomplete. The results need also to be integrated with other data, including, for example, findings which indicate that Denisovans, who were widespread in Asia during the Late Pleistocene, contributed 4-6% their genetic material to present-day Melanesians.

The Denisovans were named after a cave in southern Siberia where a finger bone fragment from which DNA was able to be extracted was discovered. Geneticists have now managed to sequence the entire Denisovan genome to a high degree of accuracy.

Though closely related to Neanderthals, Denisovans seem to have interbred with an unidentified species and picked up some of their DNA. "Denisovans," claims David Reich of the Harvard Medical School in Boston, "harbour ancestry from an unknown archaic population, unrelated to Neanderthals." One possibility is that these scattered DNA fragments (which constitute only about 1% of the Denisovan genome) derive from H. heidelbergensis who lived in Europe and western Asia between about 600,000 and 250,000 years ago. Another possibility for the source of the archaic genes is Homo erectus.

While new archaeological and genetic evidence about the early history of humanity continues to accumulate and the broad outlines of a plausible story are beginning to fall into place, making progress in understanding linguistic (and many other cultural) factors will be difficult. Sure, archaeological findings may throw some light on questions concerning where and when complex languages first developed amongst human populations and also on the vexed question of whether Neanderthals used complex languages. For example, there is strong archaeological evidence that behavioral and cultural changes occurred amongst modern humans about 50,000 years ago, and this may well suggest that it was at about this time that human languages similar in structure and more or less equivalent in complexity to languages spoken today first appeared. Also, evidence of subtle genetic changes – relating to the FOXP2 gene, for example – may yield clues about which populations were capable of complex language and which were not.

Theories of culture-driven gene evolution tend to support the idea that humans developed language in a piecemeal but not necessarily always gradual process. The basic notion is that the existence of some form of primitive spoken language (without complex syntax or an extensive lexicon) may have created a cultural environment in which certain small genetic changes – e.g. in the FOXP2 gene which is important for (amongst other things) the fine motor control of vocalizations – could have had huge evolutionary advantages and so spread rapidly, prompting further cultural changes which in turn would have facilitated further genetic change, and so on.

But, in the final analysis, anatomical, genetic and broader archaeological findings will only ever be able to answer very general questions about culture and language (and only to a certain degree of probability) and it is difficult to see how specific questions concerning the nature of very early languages, or questions concerning to what extent particular groups such as Neanderthals or Denisovans developed their own languages or adopted (modified versions of?) the languages developed by modern humans, could move beyond the realm of speculation.

So, even if it could be argued convincingly on the basis of archaeological and genetic evidence that a certain population (modern or Neanderthal) at a certain time was extremely likely to have used a language of comparable complexity to today's human languages, the content of such a claim would necessarily be rather thin – and indeed linguistically vacuous – if any knowledge of the nature of that language is (and must remain) inaccessible to us.

In a recent post I referred to claims made by researchers at the Max Planck Institute that linguistic contacts with Neanderthals may have left discernible traces in the structure of non-African languages. However, given the time-frames involved and the fact that we only have access – and will only ever have access – to a minuscule fragment of the relevant linguistic data, it seems highly unlikely that even the most sophisticated computational approaches will be of much use. The researchers' claims are intriguing but, I would say, far too optimistic about what the sorts of approaches they are proposing could actually achieve.

It needs to be borne in mind that the earliest true writing systems for natural languages for which we have evidence date only from the 3rd millennium BC. Educated guesses and speculations about Proto-Indo-European, the hypothesized language from which the Indo-European language family (which includes Sanskrit, Persian, Latin, Greek and the Romance, Germanic and Slavic languages) is seen to derive, take us further back, but only to about 4000 BC.

Can knowledge of the languages spoken in recent times by preliterate peoples take us further back? Probably not. Though many of these languages have been recorded and analyzed, it would be a mistake to assume, even if the associated material cultures have been relatively stable for (in some cases) tens of thousands of years, that the languages themselves have exhibited anything like a similar stability.

The history of the human languages for which we have no historical written records (usually because there was no writing system but sometimes because written records have survived only in a fragmentary state or not at all) can only be hypothesized, largely on the basis of the elaborate comparative methods devised by philologists in the 19th and early-20th centuries coupled with general speculations about the speed and nature of linguistic change and its relation to broader social and cultural changes.

So it seems clear that, while broad evolutionary developments and migrations may eventually be able to be mapped with a high degree of confidence, the cultures of our ancient, preliterate forebears will only ever be able to be characterized in very general terms. Gaining substantive knowledge of the content of their cultures and belief systems, as of the actual (as distinct from the possible) nature and structures of the languages upon which these cultures were built and depended, lies forever beyond our grasp. The evidence just isn't there.