Over a hundred planets and moons of all sizes orbit the sun, yet only Earth has intelligent life—or perhaps any life at all. What are the required conditions to foster life? Solar energy, a protective atmosphere, liquid water—but maybe much more. The record of Earth’s past shows long-term stability, punctuated by moving continents, periods of rising and falling oceans and ice ages followed by global warming. What combination of environmental variation and stability is required for life to begin and to become intelligent?
Based on the genetic diversity in human DNA around the globe, all modern humans can be traced to an ancestral source population in East Africa. The East African Rift Valley is a unique environment for the discovery of ancient hominid remains. Here, moving faults have exposed sediments of ancient lakes and rivers, and the precious fossils they conceal.
Lucy lived here 3.2 million years ago, at a time of changing climate with more seasonal variation and of savannahs replacing rainforests. The embodiment of early hominids, Lucy was about the height and weight of a modern ten-year-old girl and was fully bipedal. By standing upright, she could look over the grassland, cover longer distances, spot predators, and regulate her body temperature more efficiently.
Following Lucy came hominids with more human behaviors: stone tool making, scavenging, meat eating, hunting and mastering fire. The larger brains needed for these tasks resulted in an extended childhood, which required more complex social groups and the development of language.
Lucy’s Cradle, the Birth of Wonder chronicles these developments along the East African Rift Valley and then follows the spread of humans around the globe. From the obelisks of Axum to mountaintop observatories, humans have searched for a relationship with the heavens. Modern astronomers are continuing a magnificent journey of human vision that began over 3 million years ago when a young female hominid peered over the grassland of East Africa and saw the distant horizon beyond her fingertips.