ABSTRACT
Except for very early developments like neural nets and mechanoreceptors 600 million years ago, pigmented cup eyes 580 million years ago, and muscles by 540 million years ago, the events in this book can be loosely summarized under nine "firsts".
Notable achievements of the first three include a nervous system and paired eyes in the first vertebrate; limbs, an auditory system, and a hippocampus in the first tetrapod; and a large brain, mostly erect body, and loss of two cone types in the first eutherian.
The first primate had grasping hands and feet, with an opposable thumb and a diagonal gait; binocularly convergent eyes; several cortical motor areas; and an area V5 supporting movement perception.
The first ape had reduced olfactory bulbs, a re-evolved third cone type, sharp vision involving a fovea, and more differentiated parietal and temporal lobe areas. Leftward brain asymmetry began.
The first great ape was more encephalized, created simple vegetative tools, and could plan. Limited causal understanding, self-recognition, and a rudimentary gestural grammar possibly existed.
The first hominin was bipedal and could carry limited loads. A strong precision grip accompanied predominant right-handedness for some tasks. Global-over-local bias existed, as did the ability to form a basic theory of mind.
The first human had increased encephalization, created stone tools, and was substantially right-handed. New inferior parietal gyri aided planning, and Broca's cap was consistently present. Communication gestures had likely become more frequent.
Finally, the first modern human showed high encephalization and made increasingly sophisticated tools. The parietal lobe had expanded. Numerous language adaptations existed in the brain (e.g., increased larynx control, and interconnected Broca's and Wernicke's areas) and body (e.g., loss of the hyoid, and vocal cavity "verticalization"). A modality-free, general semantic memory had appeared.
Human evolution, however, has not ended. Among possible species-wide changes now occurring are weakening bones due to sedentary lifestyles; and lactase persistence, allowing adults to digest milk. Infant head circumference is under strong selection pressure, possibly increasing intelligence but also Caesarian births. As for the future, all we can be sure of is that as the environment changes, so must we.
