An apt name for this chapter would be “The Human Animal”. By and large, the first humans were just another animal, not a breed apart. Yet, like any animal, early Homo evolved a set of characteristics not shared by any other genus, including our closest ape cousins. Humans are as biologically unique as zebras or termites. Our large brain, bare skin, and agile tongue are just a few standout features.
Some of the most buzzworthy and controversial questions about evolution involve the characterization of human nature. What kind of diet are we “meant” to eat? Is it “natural” for humans to be monogamous? To search for answers, it is common to look to the early Pleistocene Epoch, when we (arbitrarily) seem to first recognize our ancestors as human. Although any conclusion based on the Pleistocene alone would be a pat answer, it can be insightful to review the environments in which some human behaviors were derived.
The human animal is a generalist. Originally shaped by the hot, dry plains of southeastern Africa, early human species colonized diverse ecosystems across all of Africa and southern Eurasia. The climate swings of the Quaternary ice ages further varied the landscapes that they encountered. Humans adapted by becoming intelligent and omnivorous. They learned to hunt, process, and cook food. Contrary to the paleo-diet fad, the human digestive and immune systems are now reliant on high quality meat and / or cooked food.
Late hominins or early humans underwent major changes in life history. Infants were born more helpless, childhood grew longer, females stopped signaling ovulation and became more monogamous, and males competed less with each other and bonded more with their mates and children. These trends all apparently contributed to formation of the nuclear family. Humans are highly social, though for millions of years their communities were no larger than loosely affiliated bands of extended families. Thus, what we think of as traditional marriage is suited specifically for that sparsely populated foraging environment (and for people with short lifespans). Variations on the theme might be just as “natural” in different settings.
Early humans were the smartest animal, yet they were still underdeveloped as intellectual beings. It is tantalizing to imagine what drove the big brain bang. The most popular hypotheses propose that braininess was forced by social competition and / or the creation of tools. Alternatively, it may have been a biological byproduct of juvenilization, a developmental carryover of childlike features (like large heads) into adulthood.
The first inklings that humans had mental powers beyond the other animals were stone tools, dating back to hominins 3 MYA, and the use of fire, especially within the last million years. Otherwise, species like Homo erectus probably did not exhibit much of the spark that we now call human spirit. Its full realization would have to wait until the appearance of Homo sapiens in Chapter 5.
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