c. 4.6 billion years ago (“bya”)

To revisit the Neanderthal split from about 500 kya, stayed in West Asia and Africa. When evidence of came to light, some scientists placed the beginning of the at about 500 kya. Stone tools have recently been dated using , which works for stone tools heated by fires, and using . That method measures water absorption into the surface of obsidian tools. For dating artifacts before the appearance of behaviorally modern humans about 70-50 kya, will not work, but successful. Neanderthals dominated Europe and today’s Middle East while home was Africa, and they also ranged to Europe and West Asia. Whether existed for only a half-million years or a million is controversial today, but what is not very controversial is that it is probably the direct ancestor of both Neanderthals and , and the first members of our species appeared in Africa about 200 kya. There is evidence that other descendants of may have existed, and . It also could have been a Neanderthal descendant. As with the discovery of the “” of Flores Island, it will not be surprising if scientists find more species that branched off of those early human and protohuman lines and died out when behaviorally modern humans spread across Africa and Eurasia.

Below is a diagram of two hydrogen atoms before and after reaction, as they bond to form H2.

From their through their and in the Eocene, primates continued evolving. About 35 mya, and monkeys, called (also called simians or anthropoids), split. Simians seem to have split from a group also ancestral to . Today’s prosimians include , , , and . During the , Africa and Southeast Asia became primate refugia. Tarsiers have , and the live on islands near Southeast Asia. Primate history in the late Eocene and Oligocene is controversial today. The fate of an from primates’ is debated, but they seem at least cousins to ancestors of , if not ancestral to them.

Organisms begin to capture chemical energy.

Those energy and chemistry concepts should make this essay easier to digest.

Although has a long history in the human line, permanent sedentism began by harvesting nuts and seeds. In the , in a swath of land that includes today’s Israel and Syria, about 13.5 kya the culture (c. 18 kya to 12.5 kya) made acorns and pistachios a dietary staple. Mortars and pestles were in the Kebaran toolkit for processing acorns, which must be pounded into a paste and soaked to leach out , and that work fell exclusively to women. Domestication often meant artificial selection to reduce/remove plant features that protected against grazing. That made the plants more palatable to humans, but it also made them more attractive to other animals. What all major crops developed by humans had in common was the domesticated plants' existence in tropical or warm temperate regions with a dry season. Those plants developed strategies to survive the dry season and stored energy in seeds, roots, and legumes. People learned to exploit that stored energy and they domesticated those plants. Many of today’s domestic crops could not survive in the wild, and protecting crops from other animals and competition from other plants has been an integral part of the Domestication Revolution. Similarly, many domestic animals would have a difficult time surviving in the wild, including people.

The most complex aquatic ecosystem appears.

Europe was a crucible for violence probably ever since the human conquest of Neanderthals, and evidence for warfare and mass violence increases as the timeline progressed from then. But going back to those , violence is not instinctual as much as calculated, and is a response to economic scarcity above all else. However, those early religious rituals were not only a method to form group cohesion; they were also a way to condition men to throw their lives away while trying to take the lives of others. The rituals and rites of passage for men were often extremely painful ordeals that conditioned them for the short life of a warrior, and forming highly contrasting in-group/out-group beliefs that facilitated killing other people. The portion of the human brain where emotions appear to be seated, in the , is no larger than in our great ape cousins. It is well-known that fear shuts down the neocortex, as animals prepare for fight-or-flight responses, and it is no different with humans. However, the response is much more dramatic with humans, with their huge neocortexes and frontal lobes. So the human response to fear is losing much of what makes humans seemingly sentient. Those religious rituals seem designed to bypass the neocortex and form a bridge to the limbic system where emotions rule. Religion seems to have arisen as a to warfare, but that will be explored in the next chapter, which covers the civilizing of humanity, which is the .