انگیختگی ادراکی ایجاد حافظه های جدید اپیزودیک را بهبود می بخشد

First, I describe why intelligence (Spearman's g) can only be fully understood through r–K theory, which places it into an evolutionary framework along with brain size, longevity, maturation speed, and several other life-history traits. The r–K formulation explains why IQ predicts longevity and also why the gap in mortality rates between rich and poor has increased with greater access to health care. Next, I illustrate the power of this approach by analyzing a large data set of life-history variables on 234 mammalian species and find that brain size correlates r=.70 with longevity (.59, after controlling for body weight and body length). A principal component analysis reveals a single r–K life-history factor with loadings such as: brain weight (.85), longevity (.91), gestation time (.86), birth weight (.62), litter size (−.54), age at first mating (.73), duration of lactation (.67), body weight (.61), and body length (.63). The factor loadings remain high when body weight and length are covaried. Finally, I demonstrate the theoretical importance of this approach in restoring the concept of “progress” to its proper place in evolutionary biology showing why, over the last 575 million years of evolutionary competition of finding and filling new niches, there has always been (and likely always will be) “room at the top.”

In both vertebrates and invertebrates, the increments in neural complexity and brain size over the last 575 million years of evolutionary history (Fig. 1) are related not only to increasing behavioral complexity (i.e., intelligence) but also to a matrix of life-history traits. For example, across 21 primate species, Smith (1989) found that brain size correlates .80 to .90 with life span, length of gestation, age of weaning, age of eruption of first molar, age at complete dentition, age at sexual maturity, interbirth interval, and body weight. As large brains evolved, they required more prolonged and complex life histories to sustain them. Large brains are also metabolically expensive, representing 2% of body mass but consuming 5% of basal metabolic rate in rats, cats, and dogs, 10% in rhesus monkeys and other primates, and 20% in humans.

Most researchers have focused on one or two adaptations taken at the same time in specific organisms rather than on a suite of correlated characteristics coevolving over 4 billion years in many organisms, or even the full 5 million years of human evolution. However, because the life-history variables associated with brain size—such as longevity and social organization—correlate both across species and within humans, they call for a general theory to explain them (Rushton, 1985 and Rushton, 2000). Because, in the upward spiral of life, regulator genes have been identified in brain development, particularly in the ape lineage leading from mammals to humans (Evans, Anderson, Vallender, Choi, & Lahn, 2004), these might be relevant for understanding not just g, but the whole suite of traits that make up the r–K dimension. The once traditional view that man is the most “advanced” of species gains novel support from the perspective of an r–K dimension. If man can no longer boast of being “created in the image and likeness of God,” he may, at least, take pride in having evolved to be the most K species on earth.