Until fossils were recognized for what they were, the (c. 541 to 485 mya) was considered to have produced the earliest known fossils, and that situation vexed scientists from Darwin onward. If animals just came into existence from nothing, the Creationist arguments of Darwin’s time may have had some validity. Darwin attributed the lack of Precambrian fossils to the geological record’s imperfection. As this essay’s previous sections have shown, scientists have filled many gaps and Darwin’s theory has held up well.
Readers for the collective task that I have in mind need to become familiar with the scientific process, partly so they can develop a critical eye for the kinds of arguments and evidence that attend the pursuit of FE and other fringe science/technology efforts. For the remainder of this essay, I will attempt to refrain from referring to too many scientific papers and getting into too many details of the controversies. Following my references will help readers who want to go deeply into the issues, and many of them are as deep and controversial as the Snowball Earth hypothesis and aftermath has proven to be, or attempts to explain the . These are relatively new areas of scientific investigation, partly due to an improved scientific toolset and ingenious ways to use them. It is very possible that the controversies in those areas will diminish within the next generation as new hypotheses account for increasingly sophisticated data, and in the near future are nearly certain. But science is always subject to becoming dogmatic and hypotheses can prevail for reasons of wealth, power, rhetorical skill, and the like, not because they are valid. The history of science is plagued with that phenomenon, and probably will be as long as humanity lives in the era of scarcity.
The Cambrian Explosion’s iconic animal was the . As a child, I read every paleontology text in my elementary school’s library, and I have fond memories of imagining trilobite lives. Was there love among the trilobites? Among the protists? The bacteria? To a scientist, those questions might be unanswerable and even meaningless, but a mystic might pursue them. I will not wax too mystically in this essay (I do it ), but that may well be the big question of life on Earth and . The nature of consciousness and love in the Cambrian, or the lack thereof, as much as it may always be a mystery, does not invalidate life’s arc through the evolutionary process; it only challenges materialism.
In 508 BCE, Athens entered its classical period, which lasted for nearly two centuries. In those two centuries, so much was invented by Greek philosophers and proto-scientists that it has been studied by scholars for thousands of years. One provocative question that scholars have posed is why the Industrial Revolution did not begin with the Greeks. The answer seems to be along the lines of Classic Greeks not having the social organization or sufficient history of technological innovation before wars and environmental destruction ended the Greek experiment. The achievements of Greece over the millennium of their intellectual fecundity are far too many to explore in this essay, but briefly, the Greeks invented: , , , the , a monetized economy, thought, such as , while developing other branches to unprecedented sophistication, and , which included the idea that . Long after the Classic Greek period was over, Hellenic intellectuals and inventors kept making innovations that had major impacts on later civilizations, such as Heron of Alexandria (or some other Greeks) inventing the and .
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As the megafauna that fueled humanity’s global expansion went extinct, all human populations became relatively immobile, and even hunter-gatherers had proscribed ranges. There were no more virgin continents to fill with people, and then humans began to turn on each other in earnest as they fought over their reduced energy supplies. Between the and the human warfare of the late hunter-gatherer phase, there seems to have been an intermediate stage that lasted from up to a million years ago among . Until hunter-gatherers began forming segmented societies (with some hierarchy) in the past 30 thousand years or so, the risks of killing one’s neighbor outweighed the advantages, especially when resolving conflicts meant easily moving to new, unoccupied lands. Although there was probably plenty of interpersonal violence, warfare did not appear until there was resource competition among the humans that conquered Earth. It is even speculated that when left Africa nearly two mya, it .
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The (c. 5.3 to 2.6 mya) began warmer than , but was the prelude to today’s ice age, as temperatures steadily declined. An epoch of less than three million years reflects human interest in the recent past. Geologically and climatically, there was little noteworthy about the Pliocene (although the was created then), although two related events made for one of the most interesting evolutionary events yet studied. South America kept moving northward, and the currents that once in the Tethyan heyday were finally closed. The gap between North America and South America began to close about 3.5 mya, and by 2.7 mya the current land bridge had developed. Around three mya, the began, when fauna from each continent could raft or swim to the other side. South America had been isolated for 60 million years and only received the stray migrant, such as rodents and New World monkeys. North America, however, received repeated invasions from Asia and had exchanges with Europe and Greenland. North America also had much more diverse biomes than South America's, even though it had nothing like the Amazon rainforest. The ending of South America’s isolation provided the closest thing to a controlled experiment that paleobiologists would ever have. South America's fauna was devastated, far worse than European and African fauna were when Asia finally connected with them. More than 80% of all South American mammalian families and genera existing before the Oligocene were extinct by the Pleistocene. Proboscideans continued their spectacular success after leaving Africa, and species inhabited the warm, moist Amazonian biome, as well as the Andean mountainous terrain and pampas. The also invaded and thrived as a mixed feeder, grazing or browsing as conditions permitted. In came cats, dogs, camels (which became the ), horses, pigs, rabbits, raccoons, squirrels, deer, bears, tapirs, and others. They displaced virtually all species inhabiting the same niches on the South American side. All large South American predators were driven to extinction, as well as almost all browsers and grazers of the grasslands. The South American animals that migrated northward and survived in North America were almost always those that inhabited niches that no North American animal did, such as monkeys, (which survived because of their claws), and their small cousins (which survived because of their armor), , and (which survived because of their quills). The opossum was nearly eradicated by North American competition but survived and is the only marsupial that made it to North America and exists today. One large-hoofed herbivore survived: the . The (it weighed one metric ton!) survived for a million years after the interchange. , that , also survived and migrated to North America and lasted about a million years before dying out. In general, North American mammals were , which resulted from evolutionary pressures that South America had less of, in its isolation. They were able to outrun and outthink their South American competitors. South American animals made it past South America, but none of them drove any northern indigenous species of note to extinction.
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This chapter falls at about this essay's midpoint, and humanity's role in this story has yet to be told. As I conceived this essay, studied for it, wrote it, edited it, and had numerous allies help out, an issue repeatedly arose regarding the half of this essay just completed, and can be summarized with: "What was the point?" Not everybody asked it and some understood, but others wondered openly and sometimes subtly what the purpose of this essay's first half was (and some asked if the essay had any point at all and considered my effort a waste of time). This chapter is my reply, and I think it is important to understand.