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”.
Continue reading “Experiments in cultural transmission and human cultural evolution”
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.
Continue reading “Cultural innovation, Pleistocene environments and demographic change”
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).
Continue reading “Culture and the human genome: a synthesis of genetics and the human sciences”
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.
Continue reading “Cumulative Culture Evolved to Rapidly Coordinate Novel Behaviours”
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).
Continue reading “What conclusions can we draw from Neanderthal DNA pt.2”
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?
Continue reading “What conclusions can we draw from Neanderthal DNA pt.1”
Originally identified by Reil (1809) and subsequently named by Burdach (1819), the arcuate fasciculus is a white-matter, neural pathway that intersects with both the lateral temporal cortex and frontal cortex via a “dorsal projection that arches around the Sylvain fissure.” (Rilling et al., 2008, pg. 426). Classical hypotheses saw this pathway as a critical component in connecting two centres of language: Broca’s area (speech production) and Wernicke’s area (speech comprehension) (Catani and Mesulam, 2008).
Much of these assumptions were based on a tentative relationship between language-impairment and damaged portions of the brain. Notably, damage to the arcuate fasciculus is implicated in a syndrome known as conduction aphasia, where an individual has difficulty in speech repetition. Often characterised by errors in spontaneous speech, an individual with conduction aphasia will be fully aware of their mistake, retaining well-preserved auditory comprehension and speech production while also being syntactically and grammatically correct (ibid).
Continue reading “Discerning the role of the arcuate fasciculus in speech processing pt.1”
A prominent idea in linguistics is that humans have an array of specialised organs geared towards the production, reception and comprehension of language. For some features, particularly the physical capacity to produce and receive multiple vocalizations, there is ample evidence for specialisation: a descended larynx (Lieberman, 2003), thoracic breathing (MacLarnon & Hewitt, 1999), and several distinct hearing organs (Hawks, in press). Given that these features are firmly in the domain of biology, it makes intuitive sense to apply the theory of natural selection to solve the problem: humans are specially adapted to the production and reception of multiple vocalizations.
Continue reading “Language as a complex adaptive system”
A developing interest of mine is that of complex adaptive systems. Like language, ant colonies and the immune system, the economy is such an evolutionary system. As Plektix explains in a very interesting article:
Continue reading “The economy as an evolutionary system”
The debate concerning the origin of our minds stems back to the diverging opinions of Darwin (1871) and Wallace (1870). When Charles Darwin first discussed the evolution of our seemingly unique cognitive faculties, he proposed that there is “no fundamental difference between man and the higher mammals in their mental faculties.” (Darwin, 1871, pg. 66). Conversely, Wallace was suspicious of whether natural selection alone could have shaped the human mind, writing: “[…] that the same law which appears to have sufficed for the development of animals, has been alone the cause of man’s superior mental nature, […] will, I have no doubt, be overruled and explained away. But I venture to think they will nevertheless maintain their ground, and that they can only be met by the discovery of new facts or new laws, of a nature very different from any yet known to us.” In the intervening years, the debate surrounding the degree of continuity between animal and human minds still rages on in contemporary discussions (Bolhuis & Wynne, 2009; Penn, Holyoak & Povinelli, 2009).
Continue reading “Continuity or Discontinuity: are our minds purely shaped by natural selection?”