Charles Darwin's (1859) theory of evolution by natural selection is among the most important scientific theories and is the most important theory in all of the life sciences. Some have even argued that the principles of Darwin's theory can explain the laws of physics and the organization of the universe (e.g., Dennett, 1995). Although Darwin's name is synonymous with evolution (which refers to the modification of traits with descent), philosophers and scholars were thinking about evolution long before Darwin. In fact, one of the first discussions of evolution pre-dates Darwin by two and a half millennia. Anaximander, a Greek philosopher, suggested that “in water the first animal arose covered with spiny skin, and with the lapse of time some crawled onto dry land and breaking off their skins in a short time they survived.” Even Darwin's grandfather, Erasmus Darwin, wrote of common ancestry and speciation. What Charles Darwin (1859) provided, however, was a viable working mechanism of evolution: natural selection. Darwinian selection has become the centerpiece of biology, and in the last few decades, many psychologists and anthropologists have recognized the value of employing an evolutionary perspective in their work (for early writings see Barkow, Cosmides, and Tooby, 1992; Chagnon and Irons, 1979; Daly and Wilson, 1983; Symons, 1979). With a focus on evolved psychological mechanisms and their information processing, evolutionary psychology has risen as a compelling and fruitful approach to psychological science. This chapter provides an introduction to evolution by natural selection and its modern application to the study of human behavior and cognition.

Introduction

The evolution of human intelligence is one of the outstanding problems in the sciences of life and mind. It is a problem that so struck Alfred Russel Wallace, the codiscoverer of natural selection, that he categorically ruled out evolutionary hypotheses and invoked divine infusion as the source of higher cognition in humans. This turn by Wallace has become a paradigmatic illustration of the difficulty and fascination that attends the scientific investigation into the genesis of our extraordinary cognitive powers (Gould, 1980).

Although in many ways as daunted as their great predecessor, few psychologists and human evolutionists today endorse Wallace's solution. In the modern context the problem appears to pose two aspects with an as-yet uncertain degree of interdependence. The first aspect addresses the species-universal architecture of human cognition and its antecedents in more basal systems (Pinker, 1997). The second aspect is concerned with quantitative differences among individuals along dimensions of cognitive abilities and changes in the distributions of the traits represented by these dimensions over the course of evolutionary time. This second aspect, however, has been less well explored by evolutionary psychologists and other workers concerned with the stated outstanding problem. The aim of this chapter with respect to this underdevelopment is twofold: (1) to propose possible resolutions to problematic issues that may to some extent be responsible for this relative neglect, and (2) to discuss future prospects for the integration of differential psychology into human evolutionary studies.

Introduction

The question about when and how language emerged in human evolution has been a major and intriguing question since at least the classical Egyptian times. It is reported that the Pharaoh Psamtik took two children to be raised by deaf-mutes, in order to find out what was the first and natural language. When these children were later observed, one of them said something that sounded like bekos, the Phrygian word for bread. From this, Psamtik concluded that Phrygian was the first and original language. During the following centuries, the origin of language continued as a most intriguing and polemic question. Different approaches and interpretations were proposed throughout history. At a certain point the debate became so complex and hot that in 1866 the Linguistic Society of Paris banned discussion of the origin of language, arguing that it is an unanswerable problem.

Contemporary research on linguistics, archeology, comparative psychology and genetics has significantly advanced understanding of the origins of human language (e.g., Bickerton, 1990; Corballis, 2002, 2006; Enard et al., 2002; Mallory, 1989; Nowak and Krakauer, 1999; Ruhlen, 1994; Swadesh, 1967; Tallerman, 2005). Different disciplines have contributed from their own perspective to make the human communication system more comprehensible.

The purpose of this paper isnot to further review anddiscuss thehistorical origins of language, but to relate what is known (or supposed) on the origins of language, with contemporary neurology and neuropsychology data, particularly with the area of aphasia.

Conceptual frameworks

What was the interplay of biological and cultural evolution in yielding modern humans with their rich, flexible, and diverse languages? What has biological evolution contributed to the innate capabilities of the human brain that allow human children to master language and how has society evolved to develop those capabilities? I approach these questions through analysis of the recent development of two new sign languages: Nicaraguan Sign Language (NSL), which developed in just 25 years within a community of deaf Nicaraguans, and Al-Sayyid Bedouin Sign Language (ABSL), which developed over a period of at most 70 years in a community of deaf and speaking Bedouin. Understanding the tradeoff between innate capabilities and social influences in the emergence of NSL and ABSL will ground an understanding of how these modern social influences may differ from those available to early humans at the dawn of language.

The mirror system hypothesis (MSH) is a specific theory of the evolution of the human “language-ready brain.” It is informed by the view that language is a multimodal system of production and performance that involves voice, hands, and face. Speaking humans accompany their speech with facial expressions and cospeech gestures of the hands (Kendon, 2004; McNeill, 1992, 2005), while many deaf people employ signed languages that are very different from spoken languages – with specific signs (which may integrate arm, hand, and face movements) that are part of a conventionalized system with limited resemblance to cospeech gestures. Details of MSH are set forth in Arbib (2005a, developing the insights of Arbib and Rizzolatti, 1997; Rizzolatti and Arbib, 1998), with commentaries and a response.

Introduction

The study of domain specificity is the study of the fit between the properties of information processing systems and the properties of information that they process. Critical to this enterprise is the fact that information processing systems do not process information randomly. This gives rise to an inevitable relationship: every information processing system does something systematic with information, and that, in turn, delineates a domain. The question of what kind of information a system operates on therefore depends critically on what it does with that information, which in turn depends on its function. This is a version of the idea of “form-function fit” in biology, applied specifically to the realm of information processing, and it is the central tenet of the study of domain specificity as I will define it here.

The rest is in the details. Those details, however, are so critically important in any given case that they make the central tenet almost useless by itself. It is true that mechanisms entail domains. However, nothing follows specifically from this fact about how many adaptations the mind must contain “how specialized” they must be. The answers to those questions depend on particular details of evolutionary history. However, when knowledge of that history is combined with principles of cognitive engineering, the central principle of domain specificity is a powerful tool for the empirical exploration of mind design. The rest of the chapter will be devoted to explaining this principle, showing how it manifests in actual cognitive architecture, and exploring how it can be used as a tool for research.

Introduction

The human face has been a source of great interest to psychologists and other scientists in recent years because of the extraordinarily well-developed ability of humans to process, recognize, and extract information from others' faces. Our magazines and television screens are not just filled with any faces – they are filled with attractive faces, and both women and men are highly concerned with good looks in a potential partner (Buss and Barnes, 1986). Physical appearance is important to humans and there appear to be certain features that are found attractive across individuals and cultures (Langlois et al., 2000). The same holds true across the animal kingdom: most nonhuman species rely on external factors, such as the size, shape, and color of adornments (e.g., feathers, fur, and fins) to attract mates (Andersson, 1994). Research on animals has focused on individual traits that are attractive across individuals, and even species, such as symmetry (e.g., Møller and Thornhill, 1998).

An evolutionary view assumes that perception and preferences serve an adaptive function: the external world provides information to guide biologically and socially functional behaviors (Zebrowitz-McArthur and Baron, 1983). If in our evolutionary past, information was present about a person's value (e.g., genetic quality) in any way, then an advantage would accrue to those who utilized these signs and those individuals would leave more genes behind in the next generation. Theoretically then, preferences guide us to choose mates that will provide the best chance of our genes surviving. In many studies this evolutionary view of attractiveness has been used to predict the specific characteristics of attractive faces (Thornhill and Gangestad, 1999 for review).

The evolution of general fluid intelligence

In the decades following Darwin's (1859) publication of On the Origin of Species, there was a flurry of proposals and theories regarding human evolution (Darwin, 1871; Huxley, 1863; Wallace, 1864), including the evolution of human intelligence. The proposals of these early evolutionists were very similar to theories of cognitive and intellectual evolution offered by this generation's theorists (Alexander, 1989; Ash and Gallup, 2007; Dunbar, 1998; Flinn, Geary, and Ward, 2005; Geary, 2005; Kanazawa, 2004, 2007; Kaplan, Hill, Lancaster, and Hurtado, 2000; Miller, 2000; Mithen, 1996, 2007). Many of the themes and contrasting views that emerged during the middle decades of the nineteenth century are echoed by theorists in the first decade of the twenty-first century. The central theme that cuts across generations and theories is that the core of intelligence is the ability to anticipate and predict variation and novelty and to devise strategies to cope with this novelty. The core issue that divides theorists is the source of novelty; specifically, whether the primary source of this variation is due to climatic change, the vagaries and nuances of hunting other species, or from the dynamics of competition within and between human groups. Darwin (1871, pp. 158–160) suggested that each of these contributed to the evolution of human intelligence: