We are all one with creeping things;
And apes and men
Blood-brethren.
From ‘Drinking Song’ by Thomas Hardy
The consensus among the scientific community is that the Earth is a planet orbiting a fairly typical star, one of many billions of stars in a galaxy among billions of galaxies in an expanding universe of enormous size, which originated about 14 billion years ago. The Earth itself formed as the result of a process of gravitational condensation of dust and gas, which also generated the Sun and other planets of the solar system, about 4.6 billion years ago. All present-day living organisms are the descendants of self-replicating molecules that were formed by purely chemical means, more than 3.5 billion years ago. The successive forms of life have been produced by the process of ‘descent with modification’, as Darwin called it, and are related to each other by a branching genealogy, the tree of life. We human beings are most closely related to chimpanzees and gorillas, with whom we shared a common ancestor 6 to 7 million years ago. The mammals, the group to which we belong, shared a common ancestor with living species of reptiles about 300 million years ago. All vertebrates (mammals, birds, reptiles, amphibia, fishes) trace their ancestry back to a small fish-like creature that lacked a backbone, which lived over 500 million years ago. Further back in time, it becomes increasingly difficult to discern the relationships between the major groups of animals, plants, and microbes, but, as we shall see, there are clear signs in their genetic material of common ancestry.
Less than 450 years ago, all European scholars believed that the Earth was the centre of a universe of at most a few million miles in extent, and that the planets, Sun, and stars all rotated around this centre. Less than 250 years ago, they believed that the universe was created in essentially its present state about 6,000 years ago, although by then the Earth was known to orbit the Sun like other planets, and a much larger size of the universe was widely accepted. Less than 150 years ago, the view that the present state of the Earth is the product of at least tens of millions of years of geological change was prevalent among scientists, but the special creation by God of living species was still the dominant belief.
The relentless application of the scientific method of inference from experiment and observation, without reference to religious or governmental authority, has completely transformed our view of our origins and relation to the universe, in less than 500 years. In addition to the intrinsic fascination of the view of the world opened up by science, this has had an enormous impact on philosophy and religion. The findings of science imply that human beings are the product of impersonal forces, and that the habitable world forms a minute part of a universe of immense size and duration. Whatever the religious or philosophical beliefs of individual scientists, the whole programme of scientific research is founded on the assumption that the universe can be understood on such a basis.
Few would dispute that this programme has been spectacularly successful, particularly in the 20th century, which saw such terrible events in human affairs. The influence of science may have indirectly contributed to these events, partly through the social changes triggered by the rise of industrial mass societies, and partly through the undermining of traditional belief systems. Nonetheless, it can be argued that much misery throughout human history could have been avoided by the application of reason, and that the disasters of the 20th century resulted from a failure to be rational rather than a failure of rationality. The wise application of scientific understanding of the world in which we live is the only hope for the future of mankind.
The study of evolution has revealed our intimate connections with the other species that inhabit the Earth; if global catastrophe is to be avoided, these connections must be respected. The purpose of this book is to introduce the general reader to some of the most important basic findings, concepts, and procedures of evolutionary biology, as it has developed since the first publications of Darwin and Wallace on the subject, over 140 years ago. Evolution provides a set of unifying principles for the whole of biology; it also illuminates the relation of human beings to the universe and to each other. In addition, many aspects of evolution have practical importance; for instance, pressing medical problems are posed by the rapid evolution of resistance by bacteria to antibiotics and of HIV to antiviral drugs.
In this book, we shall first introduce the main causal processes of evolution (Chapter 2). Chapter 3 provides some of the basic biological background, and shows how the similarities between living creatures can be understood in terms of evolution. Chapter 4 describes the evidence for evolution derived from Earth history, and from the patterns of geographical distribution of living species. Chapter 5 is concerned with the evolution of adaptations by natural selection, and Chapter 6 with the evolution of new species and of differences between species. In Chapter 7, we discuss some seemingly difficult problems for the theory of evolution. Chapter 8 provides a brief summary.
procrastinator show
lunes, 12 de marzo de 2018
preface
Cognitive neuroscience, the study of brain-behavior relationships, is
historically old in its attempt to map the brain. As a discipline it is flourishing,
with an increasing number of functional neuroimaging studies
appearing in the scientific literature daily. Unlike biology and even psychology,
however, the cognitive neurosciences have only recently begun
to apply evolutionary theory and methods. Approaching cognitive neuroscience
from an evolutionary perspective allows scientists to apply a
solid theoretical guidance to their investigations, one that can be carried
out in both human and nonhuman animals. This book represents the
first formal attempt to document the burgeoning field of evolutionary
cognitive neuroscience.
Introduction to Evolutionary Cognitive Neuroscience
All organisms were and continue to be subject to the pressures of natural
and sexual selection. These pressures are what formed all biological
organs and hence also carefully crafted animal nervous systems—the seat
of animal and human behavior, and the means by which organisms
employ information-processing programs to adaptively deal with their
environment. This theory was first formalized by Darwin (1859) in his
seminal book, On the Origin of Species by Natural Selection. Unlike the
theoretical work of early psychologists and behavioral scientists such as
Skinner and Watson, which envisioned organisms as “blank slates”
capable of making an infinite number of associations, evolutionary
metatheory is beginning to shed light on this flawed theoretical approach
to behavior analysis (see Barkow, Cosmides, & Tooby, 1992; Buss, 2005;
Cosmides & Tooby, 2005). In fact, many of the emerging studies are contending
directly with the standard social science model of psychology,
namely, that organisms possess general-purpose learning mechanisms
and that biology plays little if any role in the manifestation of behavior.
Some of the first psychological studies to demonstrate that learning is
not mediated by general-purpose learning mechanisms were conducted
several decades ago and mark what might be considered the beginning
of evolutionary thinking in psychology; they also contributed greately to
what has become known as the cognitive revolution.
In his landmark study, Garcia discovered that animals learned to
avoid novel food products that made them ill in as little as one learning
conditioning trial, something that had not been demonstrated with any
other stimulus class previously. Labeled conditioned taste aversion, this
effect describes an adaptive problem that has since been demonstrated
in almost every species tested (the exception to this rule appears to be
crocodilians; see Gallup & Suarez, 1988). This adaptation serves an
important function: don’t eat food that makes you ill, or you might not
survive to reproduce and pass on your genes. In other words, being ill
could result in a number of fitness disadvantages such as death,
inability to avoid predation, inability to search and secure mates, and
loss of mate value.
In a similar discovery, Seligman demonstrated what he referred to
as prepared learning. Prepared learning is a phenomenon in which it is
easier to make associations between stimuli that possess a biological
predisposition to be conditioned because of a role these stimuli played
in an organism’s evolutionary history. Seligman and his colleagues
demonstrated that it was much easier for humans (and animals) to form
conditioned emotional responses and associative fear responses to evolutionarily
relevant threats such as snakes, insects, and heights than it
took to condition fear to present-day threatening stimuli that subjects
were much more likely to be have encountered and be harmed by, such
as cars, knives, and guns. In other words, it was easier to condition
humans to fear snakes, spiders, and heights than it was to condition them
to fear guns, cars, and knives.
These two series of studies demonstrated that psychological traits,
like the design of bodily organs, were crafted by evolutionary forces into
adaptations that allowed our ancestors to flourish. That is, the information-processing
mechanisms designed to deal with situations such as
poisonous food or potential threats to survival evolved as part of our
ancestors’ recurrent experience with such situations. These studies refute
a key premise of the standard social science model, emphasizing that
there is no general-purpose learning mechanism. Rather, all learning is a
consequence of carefully crafted modules dedicated to solving specific
evolutionary problems (see Barkow, Cosmides, & Tooby, 1992; Pinker,
xiv Preface
2002). Our brains have evolved to be efficient problem solvers, and the
problems they are designed to solve are those that our ancestors recurrently
faced over human evolutionary history. Hence, those among our
ancestors who were psychologically adaptated to solve these problems
survived and passed the genes for those traits on to offspring.
Recently, evolutionary metatheory has been applied directly to
investigations of the cognitive neuroscience kind. For example,
O’Doherty, Perrett, and colleagues (2003) have begun to investigate
neural correlates of facial attraction. O’Doherty and colleagues discovered
that the orbitofrontal cortex appears to be activated when a person
finds a face attractive, which suggests that facial attractiveness activates
a reward system in the brain. Further, Baron-Cohen and colleagues have
demonstrated that there is a neural module dedicated to processing
socially relevant information. Baron-Cohen and colleagues demonstrated
that the ability to conceive of others’ mental states appears to be (1) a
highly modularized neurocognitive process and (2) affected by certain
neuropsychiatric pathologies (e.g., autism). Platek and colleagues have
extended initial behavioral findings of sex differences in reaction to
children’s faces to the cognitive neuroscience arena, demonstrating sex
differences in functional neural activation associated with reactions to
children’s faces. They found that males but not females showed activation
in left frontal regions of the brain when viewing self-resembling child
faces, suggesting that males inhibit negative responses to children’s faces
as a function of facial (phenotypic) resemblance.
Perhaps the most convincing set of studies demonstrating evolved
structures or modules dedicated to social interaction and exchange has
come from Cosmides, Tooby, and colleagues at the Center for Evolutionary
Psychology in Santa Barbara, California. By modifying a logic
problem known as the Wason Selection Task to reflect evolutionarily
important social interactions (e.g., cheater detection), Cosmides, Tooby,
and colleagues have demonstrated that the human brain appears to have
evolved a cheater detection mechanism that is extremely efficient. They
have furthered the evidence for a cheater detection module by showing
that one can incur impairment (i.e., brain trauma) of performance on
cheater detection problems but remain relatively unimpaired on other
types of problem solving. Their data suggest that parts of the limbic
system are implicated in the ability to detect cheaters in social
interactions.
The investigation of an evolutionary cognitive neuroscience extends
beyond humans, however. Hauser, Hare, and a number of other
researchers have been studying social behavior and social exchange
xv Preface
in nonhuman primates and have demonstrated an apparent cognitive
continuity among primate phyla in the ability to understand the mental
states of others. Daniel Povinelli’s ongoing research program has been
particularly powerful at demonstrating phylogenetic and ontogenetic
trajectories for the capacity for theory of mind and self-awareness among
nonhuman primates.
These new investigations, by applying cognitive neuroscientific
methods to answer questions posed from an evolutionary theoretical perspective,
are crafting a new understanding of how the mind and brain
evolved. In fact, they call into question much of the psychological investigation
that was conducted throughout the twentieth century. This book
is the first to present, in an organized overview, the way in which
researchers are beginning to wed the disciplines of evolutionary psychology
and cognitive neuroscience in order to provide new data on and
insights into the evolution and functional modularity of the brain.
Each of the six sections in this book addresses a different adaptive
problem. Part I consists of three chapters that outline the basic tenets of
an evolutionarily informed cognitive neuroscience. These chapters
discuss evolutionary theory as it can be applied to behavior and cognition,
as well as modern technological advances and methods that are
available to the cognitive neuroscientist for the investigation of the
adapted mind.
In Chapter 1, Aaron Goetz and Todd Shackelford present an
overview of the basic principles of evolution—natural and sexual selection,
fitness, and adaptation—as they apply to behavior and cognition.
In Chapter 2, Robin Dunbar expands on this presentation by describing
a theory known as the social brain hypothesis and discusses the major
social evolutionary forces that gave rise to big-brained humans and
adaptive brains. Chapter 3, by Shilpa Patel and colleagues, outlines
the current methodological approaches used in evolutionary cognitive
neuroscience.
Part II broaches the topic of neuroanatomy from an ontogenetic
and phylogenetic perspective. In Chapter 4, Valerie Stone considers why
big-brained organisms have extended ontogenetic and brain developmental
periods. In Chapter 5 William Hopkins considers hemispheric specialization
in our closest living relative, the chimpanzee. In Chapter 6, J.
Philippe Rushton and C. Davison Ankney review their studies on the
relationship between brain size and intelligence. To close Part II, Lori
Marino in Chapter 7 discusses the current state of the science in cetacean
brain evolution.
xvi Preface
Part III tackles the topic of reproduction and kin recognition.
Chapter 8, by Russell Fernald, discusses the degree to which social environments
can exert effects on reproductive behaviors. He draws on
studies in his own laboratory on fishes and other nonhuman organisms,
as well as on classic studies of this effect. In Chapter 9, Steven Platek
and Jaime Thomson describe their recent findings supporting a sex difference
in neural substrates involved in the detection of facial resemblance,
and discuss what these findings might mean for kin selection or
detection and paternal uncertainty. In Chapter 10, Helen Fisher and
J. Anderson Thomson, Jr., summarize their recent studies with fMRI
to identify the neural correlates of romantic attraction and lust. In
Chapter 11, David Newlin outlines his SPFit model for drug addiction,
which posits that drugs of addiction capitalize on evolutionary
predispositions for reward- and reproductive-based behavioral and
neural mechanisms.
Part IV addresses two well-known and well-researched areas:
spatial cognition and language. David Puts, Steven Gaulin, and Marc
Breedlove in Chapter 12 discuss sex differences in spatial abilities, paying
particular attention to the endocrinological aspects associated with sex
differences. In Chapter 13, Ruben Gur and colleagues extend the discussion
of the evolution of sex differences in spatial cognition by summarizing
current literature showing sex differences in neural substrates
involved in solving spatial tasks. To conclude Part IV, Michael Corballis
in Chapter 14 describes a theory of language evolution that draws
on recent findings in animal and human neuroscience, especially the
discovery of mirror neurons.
Part V takes up the topic of self-awareness and social cognition. In
Chapter 15, Laurie Santos and her colleagues summarize their recent
research showing that nonhuman primates possess the capability for
social cognition, such as rudimentary theory of mind. In Chapter 16,
Farah Focquaert and Steven Platek discuss their theory about the
evolution of self-processing, introducing evidence from the nonhuman
primate literature as well as from their own functional neuroimaging
studies. Simon Baron-Cohen in Chapter 17 then presents his systemizingempathizing
theory for the development of theory of mind and describes
how the model can be used to help classify individuals along this spectrum,
with particular reference to autism and autism spectrum conditions.
In Chapter 18, the discussion of self-awareness and social cognition
takes a different direction describing the evolution of deception. Sean
Stevens and colleages outline the “dark side of consciousness” theory,
xvii Preface
which links the capacity for deception to an intact self-awareness.
Finally, Stephen Kosslyn in Chapter 19 presents a new theory for human
motivation in which he describes social prostheses and reconsiders the self
in light of this social network.
The volume concludes with Part VI, which considers the ethical
implications for evolutionary cognitive neuroscience.
domingo, 18 de febrero de 2018
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