genetics – Page 2 – Replicated Typo

Answering Wallace's challenge: Relaxed Selection and Language Evolution

How does natural selection account for language? Darwin wrestled with it, Chomsky sidestepped it, and Pinker claimed to solve it. Discerning the evolution of language is therefore a much sought endeavour, with a vast number of explanations emerging that offer a plethora of choice, but little in the way of consensus. This is hardly new, and at times has seemed completely frivolous and trivial. So much so that in the 19th Century, the Royal Linguistic Society in London actually went as far as to ban any discussion and debate on the origins of language. Put simply: we don’t really know that much. Often quoted in these debates is Alfred Russell Wallace, who, in a letter to Darwin, argued that: “natural selection could only have endowed the savage with a brain a little superior to that of an ape whereas he possesses one very little inferior to that of an average member of our learned society”.

This is obviously relevant for those of us studying language evolution. If, as Wallace challenged, natural selection (and more broadly, evolution) is unable to account for our mental capacities and behavioural capabilities, then what is the source behind our propensity for language? Well, I think we’ve come far enough to rule out the spiritual explanations of Wallace (although it still persists on some corners of the web), and whilst I agree that biological natural selection alone is not sufficient to explain language, we can certainly place it in an evolutionary framework.

Such is the position of Prof Terrence Deacon, who, in his current paper for PNAS, eloquently argues for a role for relaxed selection in the evolution of the language capacity. He’s been making these noises for a while now, as I previously mentioned here, with him also recognising evolutionary-similar processes in development. However, with the publication of this paper I think it’s about time I disseminated his current ideas in more detail, which, in my humble opinion, offers a more nuanced position than the strict modular adaptationism previously championed by Pinker et al (I say previously, because Pinker also has a paper in this issue, and I’m going to read it before making any claims about his current position on the matter).

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Phylogenetics, Cultural Evolution and Horizontal Transmission

For some time now, evolutionary biologists have used phylogenetics. It is a well-established, powerful set of tools that allow us to test evolutionary hypotheses. More recently, however, these methods are being imported to analyse linguistic and cultural phenomena. For instance, the use of phylogenetics has led to observations that languages evolve in punctuational bursts, explored the role of population movements, and investigated the descent of Acheulean handaxes. I’ve followed the developments in linguistics with particular interest; after all, tracing the ephemeral nature of language is a daunting task. The first obvious road block is that prior to the invention of writing, the uptake of which is limited in geography and history, language leaves no archaeological record for linguists to examine. One particular note I’d like to make is that when Charles Darwin first formulated his theory of natural selection, he took inspiration from linguistic family trees as the basis for his sketch on the evolutionary tree of life. So it seems rather appropriate that phylogenetic approaches are now being used to inform our knowledge regarding linguistic evolution.

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Culture and the human genome: a synthesis of genetics and the human sciences

Humans are immersed in culture from birth. It is so fundamental to our experience, and what it means to be human itself, yet we often overlook the consideration that “cultural practices might have transformed the selection pressures acting on humans” (Laland, Odling-Smee & Myles, 2010, pg. 137).

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Cumulative Culture Evolved to Rapidly Coordinate Novel Behaviours

In the deliberations over humanity and its perceived uniqueness, a link is frequently made between our ability to support a rich, diverse culture and the origin of complex human behaviour. Yet what is often overlooked in our view of these two, clearly connected phenomena is the thread that weaves them together: the ability to coordinate behaviour. We need only look at the products of our culture, from language to religion, to see that any variant we may deem successful is contingent on coordinating the behaviour of two or more individuals. Still, what is truly illuminating about this ability is that, far from being a uniquely human feature, the ability to coordinate behaviour is ubiquitous throughout the many organismal kingdoms.

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Guns, Germs and Predictable Reviews

If, like me, you generally like the Guardian’s science features, then please avoid reading Tim Radford‘s book club discussion of Jared Diamond‘s Guns, Germs and Steel. Ever since I noticed this book was on the Guardian’s reading list, it’s been an ongoing curiosity of mine as to how they will tackle the subject. Mainly because Diamond’s book, along with Richard Dawkins’ The Selfish Gene, urged me to move into studying evolution. Sadly, and perhaps not very surprisingly, you get little from the discussion bar an unequivocal acceptance of Diamond’s central thesis: that of environmental determinism.

Nowhere is there a mention of ideas that stand somewhat in opposition to Diamond’s, such as those in the 10,000 Year Explosion. Namely, the consequences of agriculture on recent human evolution, and the growing mountain of evidence supporting the contention that different human populations have adapted to their local environments.

And just to be clear: I think Diamond’s book is a well-written, scholarly account of human history, and it’s influence is not to be understated. But I also think he overlooked a large portion of the argument.

How Culture Shaped The Human Genome

The study of culture, cultural evolution, gene-culture coevolution and niche construction have all received much more attention over the last decade. So it’s nice to see Nature taking on-board a fascinating review by Kevin Laland, John Odling-Smee and Sean Myles about how culture shaped the human genome: bringing genetics and the human sciences together. It’s really worth reading for anyone interested in the interactions between biology and culture. In particular, I was pleased to see them put forward the notion of culture having accelerated recent evolution, contra Stephen J. Gould’s claim that “there’s been no biological change in humans for 40,000 or 50,000 years”. Here’s the abstract:

Researchers from diverse backgrounds are converging on the view that human evolution has been shaped by gene–culture interactions. Theoretical biologists have used population genetic models to demonstrate that cultural processes can have a profound effect on human evolution, and anthropologists are investigating cultural practices that modify current selection. These findings are supported by recent analyses of human genetic variation, which reveal that hundreds of genes have been subject to recent positive selection, often in response to human activities. Here, we collate these data, highlighting the considerable potential for cross-disciplinary exchange to provide novel insights into how culture has shaped the human genome.

What conclusions can we draw from Neanderthal DNA pt.2

4. Nuclear DNA: Forays into 3 billion base pairs

4.1 Before Vi-80

The Vindija-80 (Vi-80) specimen is an important find for geneticists: it yielded a minimally contaminated sample and provided those first steps into Neanderthal genomics.

Previously, attempts at retrieving ancient nuclear DNA sequences proved to be a notoriously difficult process, plagued with problems of degradation, contamination and chemical damage (Hofreiter et al., 2001). Researchers also need to contend with quantities of nuclear genome available: for every nuclear genome there are approximately several hundred mtDNAs (Green et al., 2008). The severity of these problems, especially contamination, is magnified through Neanderthal genetic similarity with humans (Green et al., 2006). This is troubling because nuclear DNA presents far less variability than mtDNA (Russell, 2002). As a result, huge stretches of nuclear sequences are required to find a significant number of polymorphisms (ibid). Such implications meant that discovering endogenous DNA sequences requires sifting through a large corpus of “[…] more than 70 Neanderthal bone and tooth samples from different sites in Europe and western Asia” (Green et al., 2006, pg. 331).

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What conclusions can we draw from Neanderthal DNA pt.1

In recent times, genetic technology has progressed sufficiently to elucidate upon some of the questions normally preserved for archaeologists. One such question concerns the fate of a group of hominins that roamed Europe and East Asia for at least 250,000 years. During this time, this species adapted and endured some of the harshest environments on offer, all while showing signs of a unique culture. Only for them to suddenly disappear from the fossil record approximately 30,000 years before present (BP) (cf. Barton et al. 2007). So, what happened to our closest evolutionary relatives, the Neanderthals?

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# 12 # 19 # 22 # 26 # 36 # 41

Excuse the lack of research-based posts over the past few days, I’ve been busy packing and travelling back to my homeland. No more Scotland, sadly. I will hopefully be posting the first in a series of posts about writing systems and what the study of them can reveal to us about the interactions taking place between culture, development and genetics. That aside, my main reason for posting is because I just watched Derren Brown predict the lottery numbers. Very impressive. Watch his show on Friday 11th to find out how he did it. Until then, here is a clip from one of his previous shows:

Olfactory communication and mate choice

From the regulation and reproduction in bacteria colonies (Bassler, 2002) to complex smell and taste systems of humans (Van Toller & Dodd, 1988), the ability of sensing chemical stimuli, known as chemosensation, is believed to be the most basic and ubiquitous of senses (Bhutta, 2007). One strain of thought places chemosensation as merely an evolved ability to detect dangerous and volatile substances – such as putrefied food (see Bhutta, 2007). Still, the notion that this ability to detect chemical stimuli, particularly in the domain of smell, serves a purpose in communication is not necessarily a contemporary concept (Wyatt, 2009).

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