Category: Evolution

Intelligence: Darwin vs. Wallace

It’s Charles Darwin’s birthday today! He’s 202. So in celebration I’ve written a post on the still ongoing controversy which the theory of evolution by natural selection caused and is causing, specifically with regards to the emergence of human intelligence.

Alfred Russel Wallace is widely seen as the co-discoverer of the theory of evolution by natural selection. While Darwin had been formulating his theory from as early as the late 1830s, he kept quite about it for more than twenty years while he amassed evidence to support it. In 1858 Alfred Russell Wallace, a naturalist of the same time, sent Darwin a letter outlining for him a theory of evolution which very closely mirrored Darwin’s own. The pair co-presented their theory to the Linnaean Society in 1858 but due to Darwin’s long time amassing evidence and refining his ideas, it was his book, On The Origin of Species, which was published in 1859 and set Darwin’s name firmly in the history books as the discoverer of natural selection.

While Wallace’s part in the discovery of natural selection is far from undocumented or unknown, it is largely for presenting ‘the same ideas’ as Darwin for which he is known and what is rarely discussed in the differences in their ideas. In this post I will briefly discuss a new(ish) paper by Steven Pinker on the evolution of human intelligence and some the differences between the thinking of Darwin and Wallace on the subject.

Darwin, unsurprisingly, asserted that the abstract nature of human intelligence can be fully explained by natural selection. In opposition to this Wallace claimed that it was of no use to ancestral humans and therefore could only be explained by intelligent design:

“Natural selection could only have endowed savage man with a brain a few degrees superior to that of an ape, whereas he actually possesses one very little inferior to that of a philosopher.”(Wallace, 1870:343)

Unsurprisingly most scientists these days do not agree with Wallace on either the point that the human brain could not be the result of natural selection or that as a result of this problem it must have been a product of design by a higher being. It would be both dismissive and dull to leave the discussion at that however, which is where Pinker comes in. Despite Wallace’s argument probably coming to the wrong conclusion he does bring up some very interesting questions which need answering, namely that of; “why do humans have the ability to pursue abstract intellectual feats such as science, mathematics, philosophy, and law, given that opportunities to exercise these talents did not exist in the foraging lifestyle in which humans evolved and would not have parlayed themselves into advantages in survival and reproduction even if they did?” (Pinker, 2010:8993)

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Bipedalism: New Fossil Evidence and Language Evolution

Published in Science today, 11.02.2011 (yey! palidromic date!) is a report on the find of a Complete Fourth Metatarsal and Arches in the Foot of Australopithecus afarensis.

New fossil evidence from Hadar, Ethiopia suggests that our ancestors from 3.2 million years ago (Australopithecus afarensis (better known as Lucy)) had arches in their feet.

Arched feet are an essential part of the bipedal way that modern humans walk.

Although the skeleton of Lucy was found in 1974, until now important foot bones in all of the specimens uncovered to date have made it difficult for researchers to understand precisely how well adapted for bipedalism a. afarensis were.

Why should people interested in Language Evolution care about bipedalism? Well, here’s some food for thought:

1) Bipedalism likely had an impact on our cognitive abilities. As climbing as a form of locomotion became less common, different ways to cognitively represent space and distance probably had to be found. These new systems could have involved imitation (mirror neuron alarm bells start ringing). By adding imitative abilities to already existing spacial awareness that are seen in modern, non-human primates, this may have created mechanisms which allowed hominins to visualise themselves walking across plains (McWhinney 2005). This may have been the original selective pressure for imitative ability and therefore could have some implications for the imitative abilities which exist within language.

2) Upright posture would free up forelimbs which may have had communicative advantages as it would free the hands up for gesture. This theory has been somewhat rubished in that  the first apes to adapt a bipedal posture were probably cognitively not much different from today’s apes (assumed from evidence of skull size). However even if this was not the selective pressure FOR bipedalism it doesn’t stop it being relevant to the discussion.

3) Free hand movement would also lead to making tools. Stone tools getting more complex and language developing as evolution took place may show a close relationship between enhanced motor movement and language. Deficits in motor control are also often linked to aphasia so there is a strong connection between manual activity and speech communication.

4) When Chimpanzees and Gorillas are socializing in groups they go from a ‘knuckle walk’ to sitting in circles, this allows apes to keep eye contact with each other in social situations,  bipedalism would also allow one to keep eye contact at all times, even when in motion, and so the this may have been a selective pressure. Stanford (2003)

5) Evolution of the cortico-striatal neural circuits (basal ganglia) that regulate human language may have been shaped by the demands of upright bipedal locomotion. (Lieberman, 2001)

A lot of this debate is quite controversial but I thought I’d put some thoughts/theories out there in celebration of exciting new finds!

References

Lieberman, P. (2001) On the subcortical bases of the evolution of language. In Jurgan Trabant and Sean Ward, editors, New Essays on the Origins of Language, pages 21–40. Berlin-New York:Mouton de Gruyter.

McWhinney, B. (2005) Language Evolution and Human Development. In Bjorklund, D. and Pellegrini, A. (Eds.). Origins of the Social Mind: Evolutionary Psychology and Child Development (pp 383-410). New York: Guilford Press.

Stanford, C. B. (2003). Upright: The evolutionary key to becoming human. New York: Houghton Mifflin

Ward, C. V., W. H. Kimbel & D. C. Johanson (2011) Complete Fourth Metatarsal and Arches in the Foot of Australopithecus afarensis. Science: 331 (6018), 750-753.

Imitation and Social Cognition in Humans and Chimpanzees (II): Rational Imitation in Human Infants and Human-Raised Chimps

In my last post I wrote about two experiments on imitation in young children and chimpanzees by Lyons et al. (2005) and Horner & Whiten (2005).  Their results suggested that young children tend to copy both the ‘necessary’ and the ‘unnecessary’ parts of a demonstrator’s action who shows them how to get a reward out of a puzzle box, whereas chimps only copy the ones necessary to get the reward.

ResearchBlogging.orgOne important question raised by these experiments was whether these results can only be applied to wild chimpanzees or whether they also hold for enculturated, human-raised chimps. This is an important question because it is possible that chimpanzees raised in these kinds of richly interactive contexts show more sensitivity to human intentionality.

Buttelman et al. (2007) tested just that. They used the “rational imitation” paradigm, which features two conditions

a) the subjects are shown an action in which the specific manner of the action is not purposive and intentional but results from the demonstrator being occupied with something else. For example, he may be carrying something so that he has to use his foot to turn on a light (often called the Hands Occupied Condition).

b) the subjects are shown an action in which the demonstrator chooses a specific manner of doing something on purpose. For example he may have his hands free but still choosto turn on the light with his foot (Hands Free Condition).

taken from Call & Tomasello 2008

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Prairie Dog Communication

istockphoto.comA recent NPR radio show covered the research of the biosemiotician Con Slobodchikoff of the Univeristy of Arizone on prairie dog calls. The piece is very public-orientated, but still might be worth listening to.

ResearchBlogging.orgWe’ve all (I hope) heard of the vervet monkeys, which have different alarm calls for different predators, such as for leopard (Panthera pardus), martial eagle (Polemaetus bellicosus), and python (Python sebae). (Seyfarth et al. 1980) For each of these predators, an inherent and unlearned call is uttered by the first spectator, after which the vervet  monkeys respond in a suitable manner – climb a tree, seek shelter, etc. It appears, however, that prairie dogs have a similar system, and that it is a bit more complicated.

Slobodchikoff conducted a study where three girls (probably underpaid, underprivaleged, and underappreciated (under)graduate students) walked through a prairie dog colony wearing shirts of the colors green, yellow, and blue. The call of the first prairie dog to notice them was recorded, after which the prairie dogs all fled into their burrows. The intern then walked through the entire colony, took a break for ten minutes, changed shirts, and did it again.

What is interesting is that the prairie dogs have significantly different calls (important, as they are pretty much exactly the same to human ears) for blue and yellow, but not for yellow and green. This is due to the dichromatic nature of praire dog eyesight (for a full study of the eyesight of retinal photoreceptors of subterranean rodents, consult Schleich et al. 2010). The distinction between blue and yellow is important, however, as there isn’t necessarily any reason that blue people are any more dangerous to praire dogs than yellow ones. “This in turn suggests that the prairie dogs are labeling the predators according to some cognitive category, rather than merely providing instructions on how to escape from a particular predator or responding to the urgency of a predator attack.” (Slobodchikoff 2009, pp. 438)

Another study was then done where two towers were built and a line was strung between them. When cut out shapes were slung down the line, the prairie dogs were able to distinguish a triangle from a circle, but not a circle from a square. So, the prairie dogs are not entirely perfect at encoding information. The conclusion still stands however that more information is encoded in the calls than is entirely relevant to a suitable reaction (unless one were to argue that evolutionary pressure existed on prairie dogs to distinguish blue predators from yellow ones.)

NPR labels this ‘prairiedogese’, which makes me shiver and reminds me of Punxatawney Pennsylvania, where Bill Murray was stuck on a vicious cycle in the movie Groundhog Day, forced every day to watch the mayor recite the translated proclamation of the Groundhog, which of course spoke in ‘groundhogese’. Luckily, however, there won’t be courses in this ‘language’.

References:

Schleich, C., Vielma, A., Glösmann, M., Palacios, A., & Peichl, L. (2010). Retinal photoreceptors of two subterranean tuco-tuco species (Rodentia, Ctenomys): Morphology, topography, and spectral sensitivity The Journal of Comparative Neurology, 518 (19), 4001-4015 DOI: 10.1002/cne.22440

Seyfarth, R., Cheney, D., & Marler, P. (1980). Monkey responses to three different alarm calls: evidence of predator classification and semantic communication Science, 210 (4471), 801-803 DOI: 10.1126/science.7433999

Slobodchikoff CN, Paseka A, & Verdolin JL (2009). Prairie dog alarm calls encode labels about predator colors. Animal cognition, 12 (3), 435-9 PMID: 19116730

Imitation and Social Cognition in Humans and Chimpanzees (I): Imitation, Overimitation, and Conformity

ResearchBlogging.org

Imitation is often seen as one of the crucial foundations of culture because it is the basis of  social learning and social transmission. Only by imitating others and learning from them did human culture become cumulative, allowing humans to build and improve on the knowledge of previous generations. Thus, it may be one of the key cognitive specializations that sparked the success of the human evolutionary story:

Much of the success of our species rests on our ability to learn from others’ actions. From the simplest preverbal communication to the most complex adult expertise, a remarkable proportion of our abilities are learned by imitating those around us. Imitation is a critical part of what makes us cognitively human and generally constitutes a significant advantage over our primate relatives (Lyons et al. 2007: 19751).

Indeed, there have been some interesting experiments suggesting that the human capacity -and, above all, motivation – for imitation is an important characteristic that separates us from the other great apes.

In a series of intriguing experiments by Victoria Horner and Andrew Whiten from the University of St. Andrews in Scotland, and Derek Lyons and his colleagues from Yale University,  young wild-born chimpanzees and Children aged 3 to 4 were shown how to get a little toy turtle/ a reward out of a puzzle box. In the first condition of the experiment the puzzle box was transparent, whereas in the second condition the puzzle box was opaque.

And here’s the catch: both chimpanzees and children were not shown the ‘right’ or ‘simple’  solution to how to get the reward but one that was actually more complicated and involved unnecessary steps.

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Recursion: what is it, who has it, and how did it evolve?

Hello Hello and Happy New Year,

So a new article appeared on the internet late last year by Coolidge, Overmann and Wynn (2010) (hereafter referred to as COW because it makes me smile). It’s a really short sweet little paper and you should read it as recursion is perhaps one of the hottest topics around language evolution. This generally stems from Hauser, Chomsky and Fitch’s (HCF, 2002) claim that it is the only feature of language unique to humans. I thought it would be useful to outline some of the issues surrounding it as put forward by the COW paper due to its high-profile, controversial and important position within current issues in language evolution.

History

Recursion was first talked about within the field of linguistics by Bar-Hillel in 1953. This was before Chomsky included the concept in his Generative Grammar in 1956.

It wasn’t until 2002 that HCF made the claim that recursion was the only feature of language which was included in the faculty of language in the narrow sense (FLN) and was therefore unique to humans.

Definition

The article outlines two definitions of recursion (within linguistics):

(1) embeddedness of phrases within other phrases, which entails keeping track of long-distance dependencies among phrases

(2) the specification of the computed output string itself, including meta-recursion, where recursion is both the recipe for an utterance and the overarching process that creates and executes the recipe

I always worry when there is more than one definition for a thing because this often results in people talking past eachother or getting confused within their own arguments. These definition are also important to define before one starts making claims about whether recursion is present in species outside of humans or what people are talking about when referring to the evolution of recursion.

Evolutionary Scenarios

The paper also outlines two evolutionary scenarios for the adaptive value of recursion in human language.

(1) The gradualist position posits precursors, such as animal communication and protolanguages, and holds that the selective purpose of recursion was for communication.

(2) The saltationist position assumes no gradual development of recursion and posits that it evolved for reasons other than communication

The latter of these is the stand point taken by the HCF paper. Reasons for recursion evolving if one discounts communication could include the increase of working memory for other reasons or spacial navigation.

Pinker and Jackendoff (2005) argue that since recursion only exists in language to express recursive thoughts it must have pre-existed language.

COW (2010) points out that this is all very well but the question remains of what are recursive thoughts and why are they adaptive? These recursive acts may exist for the purposes of diplomatic speech, perlocutionary acts or for prospective memory and cognition (these are discussed at greater length in COW). These assume that the adaptive force was a social one which before Pinker and Jackendoff was not considered because recursion is often understood away from the social context of speech acts in the realm of mathematics.

Unique to Humans?

An often cited example debunking recursion’s importance to human language is the Piraha tribe who apparently do not have it (Everett 2005). The data from Everett is anecdotal, from one source and sketchy. Even if one was to accept the claims of lack of recursion they can be attributed to other factors such as cultural constraints or (although I think this is going a bit far, but then Bickerton always does go a bit too far) claiming the Piraha tribe have an underlying neurophysiological deficiency such as a limited working memory capacity or an extreme case of acquisitional delay.

COW then covers several animal studies which claim that recursion is present in animals including starlings and various monkeys. These are subject to the claim that the ability to acquire a phrase structure grammar means the presence of recursive ability (which is bollocks). These studies also fall short when one considers that starling’s songs are used to communicate emotional states, not recursive thoughts.

References

Bar-Hillel Y. (1953) On recursive definitions in empirical science. Proceedings of the 11th International Congress of Philosophy, Brussels. 1953, 5:160–165.

Coolidge, F., Overmann, K., & Wynn, T. (2010). Recursion: what is it, who has it, and how did it evolve? Wiley Interdisciplinary Reviews: Cognitive Science DOI: 10.1002/wcs.131

Hauser MD, Chomsky, N, Fitch (2002) The faculty of language: what is it, who has it and how did it evolve? Science, 298:1569-1579

http://www.st-andrews.ac.uk/~wtsf/downloads/HCF2002.pdf

“Xanadu” Revisited (Culturomics?)

Google has just released an interesting dataset. Geoff Nunberg describes it at Language Log:

Culled from the Google Books collection, it contains more than 5 million books published between 1800 and 2000 — at a rough estimate, 4 percent of all the books ever published — of which two-thirds are in English and the others distributed among French, German, Spanish, Chinese, Russian, and Hebrew. (The English corpus alone contains some 360 billion words, dwarfing better structured data collections like the corpora of historical and contemporary American English at BYU, which top out at a paltry 400 million words each.)

It is, he says, “the largest corpus ever assembled for humanities and social science research.” The New York Times has reported on it and there’s an article in Science based on it.

You can also play around with it online with the Google Books Ngram Viewer. You enter individual words or phrases (up to five words long) and a Google graphs their frequency over time. I’ve spent a little time playing around with it.

In particular, I’m interested in the proper noun, “Xanadu.” As you may know, it’s the name of Kubla Khan’s summer capital and is also the second word in Coleridge’s most famous poem, “Kubla Khan.” Several years ago I did a Google search on “Xanadu” and was surprised to come up with over two-million hits. How’d that happen? I wondered.

I ended up writing a long post on The Valve, which generated an interesting discussion, and then distilling that down into a tech report. You can download the report here (One Candle, a Thousand Points of Light: The Xanadu Meme). Here’s the abstract:

I treat a single word ‘xanadu’, as a ‘meme’ and follow it from a 17th century book, to a 19th century poem (Coleridge’s “Kubla Khan”), into the 20th century where it was picked up by a classic movie (“Citizen Kane”), an ongoing software development project (Ted Nelson’s Project Xanadu), and another movie and hit song, Olivia Newton-John’s Xanadu. The aggregate result can be seen when you google the word, you get 6 million hits. What is interesting about those hits is that, while some of them are directly related to Coleridge’s poem, more seem to be related to Nelson’s software project, Olivia Newton-John’s film and song, and (indirectly) to Welles’ movie. Thus one cluster of Xanadu sites is high tech while another is about luxury and excess (and then there’s the Manchester Swingers Club Xanadu).

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Michael Tomasello – Why We Cooperate

cross-posted at Shared Symbolic Storage

In this post I will offer a short overview of some aspects of Michael

Tomasello’s latest book „Why We Cooperate,” which is based on his 2008 Tanner Lectures on Human Values.

Tomasello deals with the question how cooperative behaviour and its socio-cognitive foundations arise both in development and during the evolution of the human species. His short text is accompanied by four short commentaries by leading scholars who contributed in important ways to the theory of the evolution and ontogenetic development Tomasello espouses here. These are: psychologist Carol S. Dweck, anthropologist Joan B. Silk, philosopher Brian Skyrms and developmental psychologist Elizabeth Spelke.

In this post I only want to briefly summarize some of the key tenets of Tomasello’s book to offer an introduction to his work on cooperation, whose main impetus it is to have a closer look at the relatively simple and primal cooperative and interactive social behaviour that builds the foundation of human culture.

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Cultural and linguistic diversity: evolutionary approaches

Via HENRY:

There’s a special issue of Philosophical Transactions of the Royal Society out on the theme of Cultural and linguistic diversity: evolutionary approaches.

From the introduction:

Evolutionary approaches to cultural change are increasingly influential, and many scientists believe that a ‘grand synthesis’ is now in sight. The papers in this Theme Issue, which derives from a sym- posium held by the AHRC Centre for the Evolution of Cultural Diversity (University College London) in December 2008, focus on how the phylogenetic tree-building and network-based tech- niques used to estimate descent relationships in biology can be adapted to reconstruct cultural histories, where some degree of inter-societal diffusion will almost inevitably be superimposed on any deeper signal of a historical branching process.

Papers:

  • On the shape and fabric of human history – Russell D. Gray, David Bryant, and Simon J. Greenhill

    • On Phylogenic Analogues

    A recent post by Miko on Kirschner and Gerhart’s work on developmental constraints and the implications for evolutionary biology caught my eye due to the possible analogues which could be drawn with language in mind. It starts by saying that developmental constraints are the most intuitive out of all of the known constraints on phenotypic variation.  Essentially, whatever evolves must evolve from the starting point, and it cannot ignore the features of the original. Thus, a winged horse would not occur, as six limbs would violate the basic bauplan of tetrapods. In the same way, a daughter language cannot evolve without taking into account the language it derives from and language universals. But instead of viewing this as a constraint which limits the massive variation we see biologically or linguistically between different phenotypes, developmental constraints can be seen as a catalyst for regular variation.

    ResearchBlogging.orgA recent post by Miko on Kirschner and Gerhart’s work on developmental constraints and the implications for evolutionary biology caught my eye due to the possible analogues which could be drawn with language in mind. It starts by saying that developmental constraints are the most intuitive out of all of the known constraints on phenotypic variation.  Essentially, whatever evolves must evolve from the starting point, and it cannot ignore the features of the original. Thus, a winged horse would not occur, as six limbs would violate the basic bauplan of tetrapods. In the same way, a daughter language cannot evolve without taking into account the language it derives from and language universals. But instead of viewing this as a constraint which limits the massive variation we see biologically or linguistically between different phenotypes, developmental constraints can be seen as a catalyst for regular variation.

    A pretty and random tree showing variation among IE languages.

    Looking back over my courses, I’m surprised by how little I’ve noticed (different from how much was actually said) about reasons for linguistic variation. The modes of change are often noted: <th> is fronted in Fife, for instance, leading to the ‘Firsty Ferret’ instead of the ‘Thirsty Ferret’ as a brew, for instance. However, why the <th> is fronted at all isn’t explained beyond cursory hypothesis. But that’s a bit besides the point: what is the point is that phenotypic variation is not necessarily random, as there are constraints – due to the “buffering and canalizing of development” – which limit variation to a defined range of possibilities. There clearly aren’t any homologues between biological embryonic processes and linguistic constraints, but there are developmental analogues: the input bottleneck (paucity of data) given to children, learnability constraints, the necessity for communication, certain biological constraints to do with production and perception, etc. These all act on language to make variation occur only within certain channels, many of which would be predictable.

    Another interesting point raised by the article is the robustness of living systems to mutation. The buffering effect of embryonic development results in the accumulation of ‘silent’ variation.  This has been termed evolutionary capacitance. Silent variation can lay quiet, accumulating, not changing the phenotype noticeably until environmental or genetic conditions unmask them. I’ve seen little research (not that I don’t expect there to be plenty) on the theoretical implications of the influence of evolutionary capacitance on language change – in other words, how likely a language is to make small variations which don’t affect language understanding before a new language emerges (not that the term language isn’t arbitrary based on the speaking community, anyway). Are some languages more robust than others? Is robustness a quality which makes a language more likely to be used in multilingual settings – for instance, in New Guinea, if seven languages are mutually indistinguishable, is it likely the that local lingua franca is forced by its environment to be more robust in order to maximise comprehension?

    The article goes on about the cost of robustness: stasis. This can be seen clearly in Late Latin, which was more robust than the daughter languages as it was needed to communicate in different environments where the language had branched off into the Romance languages, and an older form was necessary in order for communication to ensue. Thus, Latin retained usage well after the rest of it had evolved into other languages. Another example would be Homeric Greek, which retained many features lost in Attic, Doric, Koine, and other dialects, as it was used in only a certain environment and was therefore resistant to change. This has all been studied before better than I can sum it up here. But the point I am making is that analogues can be clearly drawn here, and some interesting theories regarding language become apparent only when seen in this light.

    A good example, also covered, would be exploratory processes, as Kirschner and Gerhart call them. These are processes which allow for variation to occur in environments where other variables are forced to change. The example given is the growth of bone length, which requires corresponding muscular, circulatory, and other dependant systems to also change. The exploratory processes allow for future change to occur in the other systems. That is, they expedite plasticity. So, for instance, an ad hoc linguistic example would be the loss of a fixed word order, which would require that morphology step in to fill the gap. In such a case, particles or affixes or the like would have to have already paved the way for case markers to evolve, and would have had to have been present to some extent in the original word order system. (This may not be the best example, but I hope my point comes across.)

    Naturally, much of this will have seemed intuitive. But, as Miko stated, these are useful concepts for thinking about evolution; and, in my own case especially, the basics ought to be brought back into scrutiny fairly frequently. Which is justification enough for this post. As always, comments appreciated and accepted. And a possible future post: clade selection as a nonsensical way to approach phylogenic variation.

    References:

    Caldwell, M. (2002). From fins to limbs to fins: Limb evolution in fossil marine reptiles American Journal of Medical Genetics, 112 (3), 236-249 DOI: 10.1002/ajmg.10773

    Gerhart, J., & Kirschner, M. (2007). Colloquium Papers: The theory of facilitated variation Proceedings of the National Academy of Sciences, 104 (suppl_1), 8582-8589 DOI: 10.1073/pnas.0701035104

    Gerhart, J., & Kirschner, M. (2007). Colloquium Papers: The theory of facilitated variation Proceedings of the National Academy of Sciences, 104 (suppl_1), 8582-8589 DOI: 10.1073/pnas.0701035104