The history of Earth reveals how evolution unfolds through time. Simple life held sway for much of the planet’s history. Mammals became major actors only after dinosaurs left the stage of life. From an evolutionary perspective, the rise of hairless apes happened in a heartbeat.
In the context of life’s legacy on Earth, Spokes 3 explains the elements of evolution. Evolution is coherent adaptation, not a competitive exercise in random mutation as Darwin believed.
Spokes 3 chronicles the roots of hominins, and traces the path to the emergence of humans. The book closes with early civilizations creating the patterns of polity that would continue to the present day.
From the chapter on Life’s History:
Earth has witnessed a staggering array of biota, beyond imagination in variety. This proliferation derives from evolutionary impulse to diversely adapt: to fit into niche habitats, so as to optimally exploit available energy resources.
But environments change, often dramatically. The causes are various, but all ultimately involve changes in temperature and the availability of water.
From the section on Birds:
Birds became itty-bitty by truncating the juvenile growth spurt that gave dinosaurs their girth. The shrinking process started 210 MYA and proceeded apace for 50 million years. This appears a reversion evolution back to the earliest dinosaurs, who were quite small.
Miniaturization afforded flight and novel ecological opportunities that went with it. Besides the aerodynamic advantage of carrying less weight, smaller animals can flap their wings faster than large ones.
After growth slowed to keep size down early in their evolution, avian growth sped up again, to rates even faster than the extinct dinosaurs they descended from. This lets a bird mature quickly. By the end of the Cretaceous, a bird the size of a sparrow could grow up in a week’s time.
From the chapter on Evolution:
A fundamental misunderstanding behind natural selection is that evolution is necessarily competitive: Darwin’s imagined struggle to “survival of the fittest.”
Evolution via competition would eventuate in a dearth of the population diversity which is characteristic of every species of organism. This fact alone dispels this crucial factor in Darwinism.
Evolution is not inexorably the product of competitive selection. Instead, speciation is adaptive, not some hit-or-miss selection process. Populations do not diverge from variation to speciation as a potential suicide pact.
Though every population faces survival pressures, adaptation is not a species competition, with a winner among losers that go extinct. If that were the case, chimps and other great apes would be extinct, leaving only humans. And there would not have been several hominid species during the descent of the human races.
From the chapter on Human Descent:
The emotional stature of apes and hominins is identical. Apes have an innate capacity for empathic kindness, as do many other animals. Conversely, when provoked, chimpanzees have a capacity for savagery that is positively human.
There was slight difference in intellectual capacities between chimps and early hominids. Even now, the working memory of chimps outperforms humans.
In essence, culture represents shared symbolic expression: an exhibition of abstraction in a social context. The earliest hominids had culture, just as other social animals do.
From their advent, sociality defined the success of hominids. Language was the key facility. Early on, hominids shed the sharp, pronounced canine teeth which apes use as a threat signal.
From the chapter on Early Human History:
Agriculture radically modified the habitat. In the fertile but arid regions of the Levant, where crops were first grown, irrigation succored cultivation, affording surplus food production.
This allowed higher population densities, labor diversification, trading economies, polity, accumulative culture, ideologies and depersonalized systems of knowledge, including writing. Ingrained territoriality gave birth to property regimes.
War drove human social evolution. Societies evolved from small groups, which were integrated by face-to-face cooperation; their cohesiveness reinforced by the need to further consolidate and defend local resources.
Humans emerge in Spokes 3. Spokes 4 explains the ecologies of human bodies.