selection – Page 4 – Replicated Typo

Some links #8: Are you WEIRD?

We agree it’s WEIRD, but is it WEIRD enough? Greg Downey at Neuroanthropology gives his take on Henrich et al.’s paper The weirdest people in the world? which looks at acronym WEIRD (Western, Educated, Industrialized, Rich, and Democratic) and how we may be extrapolating too much from this particularly narrow data set. Yet, despite this, we continue to use WEIRD individuals in psychological experiments, even though it may not be representative of, say, the large body of Africans. I mean, come on, you wouldn’t take genetic data from Western Europe and then make sweeping generalisations about populations in Western Africa…

The Human Penis Bone. From WEIRD to just weird. Scicurious reviews a very old journal article from 1913, which tells of a guy who actually grew a penis bone. Now, many mammals do have penis bones, but human males generally lack this ossified aid. However, if you’re curious about how to get one, then all you have to do is simply wear a particular type of corset (see below) and, here’s a downside for those of you planning on ditching the Viagra, get syphilis. As Scicurious explains:

The syphilis, combined with the constant irritation of the corset, had apparently caused a build up of desposits, which eventually ossified and turned in to bone. REAL BONE, with marrow and holes in it and everything! […] So the moral of this story is: if you’re a guy, and you’re vain about your appearance, get a flat front corset. You don’t want to be sitting down in something pointy.

Wild cat found mimicking monkey calls. Some clever vocal mimicry from a margay. ScienceDaily reports:

Researchers first recorded the incident in 2005 when a group of eight pied tamarins were feeding in a ficus tree. They then observed a margay emitting calls similar to those made by tamarin babies. This attracted the attention of a tamarin “sentinel,” which climbed down from the tree to investigate the sounds coming from a tangle of vines called lianas. While the sentinel monkey started vocalizing to warn the rest of the group of the strange calls, the monkeys were clearly confounded by these familiar vocalizations, choosing to investigate rather than flee. Four other tamarins climbed down to assess the nature of the calls. At that moment, a margay emerged from the foliage walking down the trunk of a tree in a squirrel-like fashion, jumping down and then moving towards the monkeys. Realizing the ruse, the sentinel screamed an alarm and sent the other tamarins fleeing.

Nongenetic selection and evolution: flies use bacteria to adapt to parasitic worms. Jerry Coyne has a fascinating post about nongenetic evolution occurring in a mushroom-eating fruit fly Drosophila neotestacea. But how is it nongenetic? Well, as Jerry explains:

A new paper by John Jaenike and his colleagues in Science, however, shows a form of biological evolution by natural selection that isn’t based on changes in genes. It’s based on changes in the presence of symbiotic bacteria that protect a species from parasites […] Some flies also carry another organism: the bacterial symbiont Spiroplasma, which is found in many insects. In D. neotestacea, however, the presence of Spiroplasma protects the fly from the sterilizing effects of nematodes. While flies with worms and no Spiroplasma are virtually sterile, the presence of the bacteria confers almost normal fertility on worm-ridden flies. It’s not yet clear how this works, but worms in flies with Spiroplasma are much smaller than those without the bacteria. Presumably the bacteria does something to the worms (or to the flies) that makes the worms grow much more slowly.

Some Links #6: We are all Keynesians now. Yeah, but which type?

If you think economic cuts are necessary, you’re being fooled. Martyn Winters (known to me as dad) writes about Joseph Stiglitz’s thoughts on George Osborne’s attempts to reduce the deficit:

You may have heard of Professor Joseph Stiglitz – he’s the Nobel laureate economist who correctly predicted the global crash. He’s distinctly unimpressed with Osbourne’s budget. This, he predicts, will make Britain’s recovery from recession longer, slower and harder than it needs to be. The rise in VAT could even tip us into a double-dip recession. He took time to offer George Osbourne a bit of advice – which will probably go unheeded, because Osbourne’s objectives aren’t necessarily to improve the economy. They are an ideological attack on the state, with the intention of shrinking it by forty percent.

The basis for this is part Keynesian, and has been echoed by other commentators such as Johann Hari, in that we must spend our way out of economic woes. Now I must admit I’m not too fond of how Osborne is going about reducing deficit (raising VAT… huh?), but, for reasons that’ll become apparent below, I do think we need to tackle the deficit.

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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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Experiments in cultural transmission and human cultural evolution

For those of you familiar with the formal mathematical models of cultural evolution (Cavalli-Sforza & Feldman, 1981; Boyd & Richerson, 1985), you’ll know there is a substantive body of literature behind the process of cultural transmission. It comes as a surprise, then, that experiments in this area are generally lacking.

For instance, if we look at evolutionary biology, then there are many experiments into small-scale microevolutionary processes, such as natural selection, sexual selection, mutation and drift, which are then applied in showing how these processes generate population-level, macroevolutionary patterns. It follows then, that this sort of population-level thinking can be applied to cultural evolution: the forces and biases of cultural transmission can be studied experimentally to see if they fit with population-level patterns of cultural change documented by scientists. As the current paper by Mesoudi & Whiten (2008) notes, this potentially gives cultural transmission experiments added significance: “cultural transmission should not only be studied for its own sake (i.e. in order to better understand cultural transmission itself), but also in order to explain broader cultural patterns and trends, all as part of a unified science of cultural evolution”.

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Cultural innovation, Pleistocene environments and demographic change

It is well documented that Thomas Robert Malthus’ An Essay on the Principle of Population greatly influenced both Charles Darwin and Alfred Russell Wallace’s independent conception of their theory of natural selection. In it, Malthus puts forward his observation that the finite nature of resources is in conflict with the potentially exponential rate of reproduction, leading to an inevitable struggle between individuals. Darwin took this basic premise and applied it to nature, as he notes in his autobiography:

In October 1838, that is, fifteen months after I had begun my systematic inquiry, I happened to read for amusement Malthus on Population, and being well prepared to appreciate the struggle for existence which everywhere goes on from long-continued observation of the habits of animals and plants, it at once struck me that under these circumstances favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The results of this would be the formation of a new species. Here, then I had at last got a theory by which to work.

The interaction of demographic and evolutionary processes is thus central in understanding Darwin’s big idea: that exponential growth will eventually lead to a large population, and in turn will generate competition for natural selection to act on any heritable variation which conferred a greater fitness advantage. Under these assumptions we are able to interpret the evolutionary record of most species by appealing to two basic causal elements: genes and the environment. As we all know, in most cases the environment generates selection pressures to which genes operate and respond. For humans, however, the situation becomes more complicated when we consider another basic causal element: culture. The current paper by Richerson, Boyd & Bettinger (2009) offers one way to view this muddied situation by delineating the demographic and evolutionary processes through the notion of time scales:

The idea of time scales is used in the physical environmental sciences to simplify problems with complex interactions between processes. If one process happens on a short time scale and the other one on a long time scale, then one can often assume that the short time scale process is at an equilibrium (or in some more complex state that can be described statistically) with respect to factors governed by the long scale process. If the short time scale and long time scale interact, we can often imagine that at each time step in the evolution of the long time scale process, the short time scale process is at “equilibrium.” A separation of time scales, if justified, makes thinking about many problems of coupled dynamics much easier.

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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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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.

Falling miserably back to Earth

I just watched the first episode of the BBC’s new show Defying Gravity, and it is absolutely awful. Clichéd characters, boring plot, and a completely unrealistic setting (it’s set in 2052, which seems to have not moved on from 2009 — the obvious exception being space travel). However, it did remind me of a recent post by one of my favourite writers, Charles Stross:

There’s an implicit feedback between such a situation and the characters who are floundering around in it, trying to survive. For example: You want to deflect that civilization-killing asteroid? You need to find some way of getting there. It’s going to be expensive and difficult, and there’s plenty of scope for human drama arising from it. Lo: that’s one possible movie in a nutshell. You’ve got the drama — just add protagonists.

I use a somewhat more complex process to develop SF. I start by trying to draw a cognitive map of a culture, and then establish a handful of characters who are products of (and producers of) that culture. The culture in question differs from our own: there will be knowledge or techniques or tools that we don’t have, and these have social effects and the social effects have second order effects — much as integrated circuits are useful and allow the mobile phone industry to exist and to add cheap camera chips to phones: and cheap camera chips in phones lead to happy slapping or sexting and other forms of behaviour that, thirty years ago, would have sounded science fictional. And then I have to work with characters who arise naturally from this culture and take this stuff for granted, and try and think myself inside their heads. Then I start looking for a source of conflict, and work out what cognitive or technological tools my protagonists will likely turn to to deal with it.

Star Trek and its ilk are approaching the dramatic stage from the opposite direction: the situation is irrelevant, it’s background for a story which is all about the interpersonal relationships among the cast. You could strip out the 25th century tech in Star Trek and replace it with 18th century tech — make the Enterprise a man o’war (with a particularly eccentric crew) at large upon the seven seas during the age of sail — without changing the scripts significantly. (The only casualty would be the eyeball candy — big gunpowder explosions be damned, modern audiences want squids in space, with added lasers!)

TV sci-fi sucks.

N.B. They just started jabbering on about natural selection and completely missed the point. So I’ll repeat: TV sci-fi sucks.

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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