Neanderthals invented more sophisticated stone tools about 300 kya, for the first significant advance in more than a million years, and their toolset is called , or . Neanderthals had the largest human-line brains ever measured, and they may have also invented the practice of , but they could from their ancestors. As with their ancestors, they and carved flesh from their corpses, in . Neanderthals seemed to be a regional human variation, adapted to colder environments, and the fact that they interbred with has caused some scientists to classify them as . If they did not become a truly separate species, they were slowly speciating as they adapted to their ice age environment. Neanderthals built shelters, may have drawn cave paintings, and engaged in activities comparable to of the time. There seems to be little reason to call them “primitive” when comparing them to , particularly the early ones. The last Neanderthals died out about 30 kya, about the same time that humans arrived in the region, and it was .
Humans took a different path 2.5 mya. There are generally two schools of thought regarding the appearance of among scientists: one is called the Multiregional Model, and the other is called the . In their essence, the Multiregional Model had those migrants eventually evolving into today’s races, and the “Out of Africa” Model had humans evolve in Africa and then spread across the world and replace/displace all other members of the genus. The rise of has largely resolved the issue in favor of the “Out of Africa” Model. There are also intermediate views and variations of each hypothesis, which generally relate to the invaders mating with the natives, even if they could be classified as separate species. For instance, Neanderthal DNA is part of the human genome, which reflects interbreeding. Since Neanderthals were largely confined to Europe and what became the Fertile Crescent, and the migration of the original was from Africa, sub-Saharan Africans . Africans also have the most genetic divergence, which reflects the idea that humans have lived longer in Africa than anywhere else. There is virtually no doubt that evolved in Africa.
The ecosystems may not have recovered from Olson’s Extinction of 270 mya, and at 260 mya came another mass extinction that is called the mid-Permian or extinction, or the , although a recent study found only one extinction event, in the mid-Capitanian. In the 1990s, the extinction was thought to result from falling sea levels. But the first of the two huge volcanic events coincided with the event, in . There can be several deadly outcomes of major volcanic events. As with an , massive volcanic events can block sunlight with the ash and create wintry conditions in the middle of summer. That alone can cause catastrophic conditions for life, but that is only one potential outcome of volcanism. What probably had far greater impact were the gases belched into the air. As oxygen levels crashed in the late Permian, there was also a huge carbon dioxide spike, as shown by , and the late-Permian volcanism is the near-unanimous choice as the primary reason. That would have helped create super-greenhouse conditions that perhaps came right on the heels of the volcanic winter. Not only would carbon dioxide vent from the mantle, as with all volcanism, but the late-Permian volcanism occurred beneath Ediacaran and Cambrian hydrocarbon deposits, which burned them and spewed even more carbon dioxide into the atmosphere. Not only that, great salt deposits from the Cambrian Period were also burned via the volcanism, which created hydrochloric acid clouds. Volcanoes also spew sulfur, which reacts with oxygen and water to form . The oceans around the volcanoes would have become acidic, and that fire-and-brimstone brew would have also showered the land. Not only that, but the warming initiated by the initial carbon dioxide spike could have then warmed up the oceans enough so that methane hydrates were liberated and create even more global warming. Such global warming apparently warmed the poles, which not only melted away the last ice caps and ended an ice age that had , but deciduous forests are in evidence at high latitudes. A 100-million-year Icehouse Earth period ended and a 200-million-year Greenhouse Earth period began, but the transition appears to have been chaotic, with wild swings in greenhouse gas levels and global temperatures. Warming the poles would have lessened the heat differential between the equator and poles and further diminished the lazy Panthalassic currents. The landlocked Paleo-Tethys and Tethys oceans, and perhaps even the Panthalassic Ocean, may have all become superheated and anoxic as the currents died. Huge also happened, which may have and led to ultraviolet light damage to land plants and animals. That was all on top of the oxygen crash. With the current state of research, all of the above events may have happened, in the greatest confluence of life-hostile conditions during the eon of complex life. A recent study suggests that the extinction event that ended the Permian may have lasted only 60,000 years or so. In 2001, a bolide event was proposed for the Permian extinction with great fanfare, but it does not appear to be related to the Permian extinction; the other dynamics would have been quite sufficient. The Permian extinction was the greatest catastrophe that Earth’s life experienced since the previous supercontinent existed in the .
The end-Permian extinction correlated rather precisely with the eruption of the , which continued for a million years and spewed millions of cubic kilometers of basalt. The end-Permian extinction was the final blow for many ancient organisms. My beloved made their final exit from Earth during the end-Permian extinction, as did tabulate and rugose corals, , and the last freshwater . Articulate brachiopods completely vanished from the fossil record, but reappeared in the Triassic via , but brachiopods never recovered their former abundance and have lived a marginal existence ever since. and disappeared along with the reefs, while complex foraminiferans and also vanished, and all of them staged comebacks in the Triassic via ghost ancestors. Bivalves suffered relatively modestly (“only” about 60% of bivalve genera went extinct) and quickly recovered, fish were barely affected, and gastropods were devastated but quickly recovered. Ammonoids went through their typical boom-and-bust pattern during the Permian extinctions, while nautiloids kept dwindling but scraped by in their deep-water exile. In the final tally, more than 95% of all marine species went extinct. Not only was the death toll tremendous, but the from before that the Permian extinction marks the end of an era, which began with the Cambrian Explosion. The ended with the Permian extinction and the began.
On land, the devastation was similar. Again, insects , and several orders of insects vanished from the fossil record after the Permian; those of Paleozoic times also vanished forever. Permian forests gave way to deciduous forests in the wake of global warming, and early gymnosperms and seed ferns were largely replaced as made a comeback in the early Triassic. The lycophyte radiation in the wake of the Permian extinction is typical of what are called , which are the first organisms to colonize disturbed environments. Reptiles and amphibians lost nearly two-thirds of their families, which translates to more than 90% of all species. All large herbivores and predators went extinct, along with gliding reptiles. In total, the Permian extinctions wiped out about 90-96% of all species, more than 80% of all genera, and nearly 60% of all families. Nothing else in the history of complex life comes close and puts the Permian extinction in a category all its own.
The that arrived in East Asia and the islands off of Southeast Asia existed, and virtually no changes are evident in their anatomy or technology for more than 1.5 million years, only to disappear about when arrived. Like finding refuge in the islands near Southeast Asia, those at the far end of the “known” world seem to have lived like country bumpkins for well over one million years, without any outside disturbances or benefits from their cosmopolitan homeland. The foregoing is largely my speculation on the issue, which could collapse like a house of cards with the Next Great Finding, and the lack of evidence for early fires is the biggest hurdle. Like Wrangham, I will follow those investigations of early fire with great interest. I doubt that any species that ever acquired the greatest technology in Earth's history would ever lose it, as it would have quickly become indispensable.
Two major events happened soon after appeared, and their sequence seems to support the Cooking Hypotheses. The first of which was the migration of from Africa ; they spread to and by 1.8 mya (perhaps 1.6 mya in the case of Java), and . It was the , and may have become the first multi-continental member of the human line, and certainly the first widespread one. Favorable climates and a lower Himalaya range and Tibetan Plateau may have encouraged that migration. Unlike Miocene apes that began to migrate from Africa 16.5 mya, there was no unbroken forest to sustain journey to East Asia. Those migrants would have to sleep on the ground for much of the journey and were not adapted for sleeping in trees, . From today’s viewpoint, it may seem that they were adventurers, but as will also become obvious with the spread of , in one individual’s lifetime, there was probably only modest movement, expanding into the next uninhabited valley or two. Such an expansion happened one valley at a time, one generation at a time, to make it across a continent in a few thousand years for those that could adapt to changing biomes. Migrating at the same latitude would not have presented great climatic issues. As those migrations happened during the ice age, they were along southern Eurasia. There is no evidence yet that ever made it to Australia, probably because of the ocean crossing required for passage.
The most-accepted hypothesis today is that evolved from and first appeared in East Africa between 2.0 and 1.8 mya. If those are not the exact species that the human line descended through during those times, our actual ancestors were close cousins. The early adults had brains of about 850 ccs, and some later specimens reached 1,100 ccs, or triple the mass of a chimpanzee’s brain. Today’s human brain only averages about 1,200 ccs (). , as with other members of the line, had a brain that was another third larger than , and probably was responsible for its relatively sophisticated material culture. But important as its growing brain was, other anatomical changes were more telling. was fully adapted for living on the ground and walking great distances. For the first quarter-million years of existence, it lived in the Oldowan culture, which used tools and weapons that were little more than rocks with sharpened edges, and probably some shaped sticks. They evolved in a highly dangerous environment and all of their ancestors slept in trees. How could they have slept on the ground? In a word: fire.
Did the control of fire to , ? Or did merely use it to begin dominating the world? Was cooking the seminal event in the appearance of humans? Those questions may not be definitively answered in my lifetime, and led to the somewhat uncertain title of this chapter. Highly transformative developments coincided with the appearance and dispersal of , which was a radical break from all that came before – biologically, technically, and culturally – and strongly implies great cognitive enhancements. I believe that the control of fire and cooking would leave deep cultural and biological impacts on the human journey, and because barely changed during its nearly two-million year tenure on Earth, both in biology and in Acheulean artifacts, I favor Wrangham’s hypothesis, at least until the Next Big Finding. Just as Einstein said that and that his theories would one day become obsolete, but that their best parts would survive in the new theories, I suspect that significant aspects of Wrangham’s hypothesis will live on in successor hypotheses, and other scientists have been following Wrangham’s lead.
I am taking some liberties in calling Turkana Boy a ; he is technically a member of , which is often considered ancestral to , which is the Asian variant’s name. There is great debate regarding how the human family tree branches between and . Some call the various -type species all subspecies of , while others argue for several distinct species. I will not stray far from the orthodox narrative here, for good reason. The reconstructed early human tale is based on very limited evidence, but that evidence will only grow over time, and the tools and techniques for using them will become more sophisticated. Although there may be some upcoming radical changes in the view of the early human journey, efforts of countless scientist and fossil hunter lifetimes support the narrative that this essay sketches, and I respect their findings and opinions, even though I acknowledge many limitations. The human ego, it seems, becomes more involved as the story of life on Earth moves closer to its human chapters.