Author: Hannah

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.

Are mirror neurons the basis of speech perception?

The discovery of Mirror Neurons in Macaque monkeys has lead to theories of the neurophysiological substrate of speech perception being grounded in mirror neurons. This is also relevant to the evolution of speech as if ability to perceive a rapid stream of phonemes is present in species such as macaques then this provides a foundation on which other linguistic abilities could have been built to form language.

A recent paper by Rogalsky et al. (2011) explores these theories by testing the hypothesis that damage to the human mirror system should cause severe deficits in speech perception. This is due to there being a number of recent studies which explore whether the areas of motor neurons are activated during speech perception but these do not address the prediction that patients with lesions in the motor regions (left posterior frontal lobe and/or inferior partiental lobule) should lack an ability to perceive speech.

Patients with Broca’s aphasia are well documented as having severe speech perception and Broca’s area is known to be an area of motor speech perception. This sets up a link between a lesions involving Broca’s area and a difficulty in speech perception. However, despite these problems in speech perception, it has been shown that Broca’s aphasics are quite capable of processing speech sounds. This creates a problem for motor theories of speech perception as it would predict the ability to percieve speech sounds when the lesion lies in Broca’s area. Rogalsky et al. (2011) states that this conclusion may not be so reliable as a lot of the group based studies which these conclusions have been drawn from do not present detailed lesion information but instead rely on clinical diagnosis of Broca’s aphasia to infer lesion location.

Rogalsky et al. (2011) present 5 cases of people with lesions which effect areas of mirror neurons.

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Project Nim

How cool is this? They’ve made a movie about Nim Chimpsky called Project Nim!

By the same guys who made Man on Wire, it’s currently been shown at the Sundance Festival.

Nim was  raised and nurtured like a human child in order to see to what extent apes could acquire human language.

SO CUTE!

Following Nim’s extraordinary journey through human society, and the enduring impact he makes on the people he meets along the way, the film is an unflinching and unsentimental biography of an animal we tried to make human. What we learn about his true nature – and indeed our own – is comic, revealing and profoundly unsettling.

 

http://sundance.slated.com/2011/films/projectnim_sundance2011

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

Mathematical Modelling 101 – The Price Equation

So in this post I’m going to assume you know absolutely nothing about anything. If you know something about something this probably isn’t what you’re looking for. If you’re looking for something which will go into depth on how the price equation is derived this probably isn’t what you’re looking for either. If you simply want to know what the price equation does and how to use it at face value then welcome! You’ve found the right place.

The price equation is used to calculate how the average value of any variant can change within a population from generation to generation.

Here I will cover everything you need to know to understand the equation and slot in the right values:

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Williams Syndrome, Modularity and Language Evolution

Williams Syndrome (WS) is a rare genetic condition which manifests itself as a severe deficit in development and IQ, however it leaves language ability largely unaffected and is, as a result, often cited as evidence for a specific language module (Bellugi et al. 1988), as language can be unaffected despite other mental deficits. This argument has a strong bearing on the evolution of language as it contributes to the debate of whether language evolved for language’s sake or whether it is as the result (an exaptation or spandrel) of general cognitive capability in other areas.

Work by Brock (2007) has shown that the language abilities of people with WS could be predicted by non-linguistic abilities (You could probably argue this of the language abilities of anyone, but that’s another blog post). It has also been shown that language acquisition in WS children is behind that of normal children. Many studies have shown deficits in WS children’s language (reflexive pronouns, grammatical morphems, verb raising, negative wh-sentences) which are generally put down to normal-but-delayed language acquisition as people with the condition will usually pick these grammatical rules up by adolescence.

Perovic and Wexler (2010) suggest that if some grammatical knowledge is shown not to be present in WS children by adolescence, (as is apparently the case with verb raising) then this is evidence to suggest not just ‘normal-but-delayed’ language, but in fact, ‘atypical’ language.

Perovic and Wexler (2010) did a study on 26 children with Williams Syndrome between the ages of 6 – 16. They were tested using picture matching comprehension tasks on passives featuring ‘actional’ verbs and ‘psychological verbs’. The results confirmed what has been seen in previous studies, that WS children can process actional passives with ease, but also showed a previously unreported deficiency in their ability to process psychological verbs.

They also found this deficiency in 5 adult sufferers of WS.

So it seems that the linguistic ability of people with WS is not so exceptional after all.

In the discussion of this paper it is explored as to whether these differences could just be down to the general cognitive impairments which people with developmental problems face. The fact that this question even needs to be discussed is evidence to contradict a ‘language module’ theory. That is that if the deficit in WS children’s passive is a specifically linguistic one then WS can no longer be used as evidence for affected intellectuality but unaffected language, and on the other hand, if it is as a result of general cognitive deficiency, then this is evidence to suggest that it is general cognitive ability that results in much, if not all, linguistic ability in the first place.

References

Bellugi, U. Marks, S. Bihrle, A. and Sbo, H. (1988) Dissociation between language and cognitive functions in Williams Syndrome. In D. Bishop and K. Mogford (Eds.) Language developement in excpetional circumstances (pp. 177 – 189). Hillsdale, NJ: Erlbraum

Brock, J. (2007) Language abilities in Williams syndrome: A critical review. Development and Psychopathology, 19, 97-127.

Perovic A, & Wexler K (2010). Development of verbal passive in Williams syndrome. Journal of speech, language, and hearing research : JSLHR, 53 (5), 1294-306 PMID: 20631227

Tool making and Language Evolution

There’s an often cited gap in tool making history in which humans did not advance from simple Oldowan tools (which date back to about 2.5 million years ago) until about 500,000 years ago when progress became much faster. There is much debate as to whether this gap in progress is the result of the cognitive abilities to make more innovative tools or if it was an issue of dexterity.

A recent article by Faisal et al. (2010) “The Manipulative Complexity of Lower Paleolithic Stone Toolmaking” has tried to address these problems by assessing the manipulative complexity of tool making tasks from the Oldowan tools to the more advanced hand axes from much later.

A stone ‘core’ (A) is struck with a hammerstone (B) in order to detach sharp stone ‘flakes’. In Oldowan toolmaking (C, top) the detached flakes (left in photo) are used as simple cutting tools and the core (right in photo) is waste. In Acheulean toolmaking (C, bottom), strategic flake detachments are used to shape the core into a desired form, such as a handaxe. Both forms of toolmaking are associated with activation of left ventral premotor cortex (PMv), Acheulean toolmaking activates additional regions in the right hemisphere, including the supramarginal gyrus (SMG) of the inferior parietal lobule, right PMv, and the right hemisphere homolog of anterior Broca's area: Brodmann area 45 (BA 45).

The following is taken from a press release from Eureka.org:

Researchers used computer modelling and tiny sensors embedded in gloves to assess the complex hand skills that early humans needed in order to make two types of tools during the Lower Palaeolithic period, which began around 2.5 million years ago. The cross-disciplinary team, involving researchers from Imperial College London, employed a craftsperson called a flintnapper to faithfully replicate ancient tool-making techniques.

The team say that comparing the manufacturing techniques used for both Stone Age tools provides evidence of how the human brain and human behaviour evolved during the Lower Palaeolithic period.

The flintnapper who participated in today’s study created two types tools including the razor-sharp flakes and hand-held axes. He wore a data glove with sensors enmeshed into its fabric to record hand and arm movements during the production of these tools.

After analysing this data, the researchers discovered that both flake and hand-held axe manufacturing techniques were equally complex, requiring the same kind of hand and arm dexterity. This enabled the scientists to rule out motor skills as the principal factor for holding up stone tool development.

The team deduced from their results that the axe-tool required a high level of brain processing.

This has implications for language evolution as brain scans from tool makers have shown significant overlap with areas involved in discourse-level language processing as well as complex hand gestures. The study finishes with the following:

…the anatomical overlap of Late Acheulean toolmaking and right hemisphere linguistic processing may reflect the flexible “mapping” of diverse overt behaviors onto shared functional substrates in the brain. This implies that: 1) selection acting on either language or toolmaking abilities could have indirectly favored elaboration of neural substrates important for the other, and 2) archaeological evidence of Paleolithic toolmaking can provide evidence for the presence of cognitive capacities also important to the modern human faculty for language.

Read the original article at PLoS ONE:

http://www.plosone.org/article/info:doi/10.1371/journal.pone.0013718

Mathematical Modelling 101 – Evolutionary Game Theory

Game Theory was fist applied to evolution by John Maynard-Smith and George Price in 1973. It differs from traditional game theory is that it focusses on dynamics of strategy change more than the properties of strategy equilibria, although equilibria still exist within EGT but are know as Evolutionary Stable Strategies as opposed to Nash Equilibria.

Dove-Hawk

Imagine a situation in which 2 members of a species come into conflict over a resource. Within this conflict each animal has the optional to ‘fight’, ‘display’ or ‘run away’. There are 2 strategies within this species, either the Dove strategy or the Hawk strategy. In the Dave strategy, upon meeting someone also adopting the Dove strategy both “Doves” display and share the resource or upon meeting a “Hawk” the Dove runs away. Adopting the Hawk strategy entails always fighting. So upon meeting a Dove the Hawk will fight and the Dove will run away and the Hawk will take all of the resource, and upon meeting another Hawk, both will fight and one will win out. On average across many interactions with other Hawks, the payoff gained ends up being (v/2)-c where v=value of resource and c=cost.

Dove Hawk
Dove v/2, v/2 v, 0
Hawk 0, v (v-c)/2, (v-c)/2

The question to ask of this game is, given values v and c, which strategy will evolutionarily win out?

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Mathematical Modelling 101 – Intro to Game Theory

This post is going to just be a very brief introduction to what Game Theory is, how it works and some basic terminology. In later posts I will get more advanced and cover how it can be applied to Cultural Evolution.

What is Game Theory?

Game theory is a branch of applied mathematics most commonly used in Economics. However, it can be very successfully applied to other social sciences as well as Evolutionary Biology. It gives both descriptive answers (what people do) and prescriptive answers (what people should do) in a given game.

Why is this relevant?

Game Theory is a very good tool in predicting outcomes, not only in the very simple games covered in this post, but also in predicting the outcomes of evolutionary strategies and of predicting outcomes for signalling games which can inform us on human and animal communicative strategies.  Running iterated games over populations can introduce interesting qualifications to these very simple ideas as well and explain some things which may, at first, appear maladaptive, as such is a very useful tool in bypassing our intuitions. It is of these things that the next few posts will explore.

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