Today we are going to examine early human evolution and briefly go over the evolutionary “mile-markers” that lead from our earliest apelike ancestors in the Miocene to the arrival culturally modern humans by 50,000 BCE. This leads to a discussion of how humans out-competed rival hominids and how humans spread throughout the world. Our final topic will be the adoption of agriculture, at which point various human groups begin to diversify in terms of wealth, health and standard of living.
The Himalayas arose (had their orogeny) during the Miocene. As the mountains rose, the climate cooled and in Africa, forests gave way to grasslands. The Great Apes are unique from other simians in that they are able to walk upright. The savannah-like environment rewarded creatures who could see for long distances and at wide angles. The line of Great Apes that contained the ancestors of modern humans were perhaps the best adapted to this grassy, treeless environment.
While other human ancestors and relatives (including chimps) have used tools, homo erectus was the first of the hominids to spread widely outside of Africa and the first to use fire. The taming of fire is an epochal event in the development of humanity. Fire allows for cooking and cooking predigests food, allowing more calories to be consumed. Big brains are needed to handle fire and big brains require extra calories – again, made possible by cooking. Don’t make the teleological mistake of assuming that fire caused big brains (or even that big brains caused fire). Brain size would have hit a natural caloric constraint or upper limit. That limit was removed through the taming of fire and the spread of cooking. The two things – fire and brain size – are mutually reinforcing and correlated, not necessarily causally related (in either direction).
One of the noticeable physical differences between early homo sapiens and other hominids is that h. sapiens is very well-adapted for long-distance running. Not just our bones and muscles but our upright posture and hairy heads helps protect us by minimizing the surface area exposed to the sun. Hairless arms and torsos allow sweat to evaporate and cool us most efficiently. Many anthropologists believe our homo sapiens-specific adaptations made us excellent at running – so good that we could run other animals to exhaustion in what is known as “persistence hunting”.
Many people have strong opinions on evolution. As you advance in your education, you will find fewer and fewer people who reject evolution. The process of natural selection – that advantageous adaptations to the environment survive while those that do not confer advantages tend to die out – is an idea with tremendous explanatory power and is accepted by virtually all educated people.
I can’t stress enough how much and how quickly life changed for Homo Sapiens about 50,000 years ago. We use words like “suddenly” to describe the acquisition of art (cave paintings), religion (burial of the dead) and composite tools (axes with stone blades and wooden handles). In reality, those changes happened over thousands of years. Did the changes occur gradually, one building on the other – or did they happen suddenly, perhaps because of the invention of language? Biologists talk about “punctuated equilibriums” – the idea that systems stay the same until suddenly, everything changes then resets to a new stable state. This idea of punctuated equilibrium would be consistent with the belief that language caused these dramatic behavioral changes.
We have a lot of forensic evidence for the Neanderthals and have even sequenced their DNA. Neanderthal DNA is found in every human subpopulation except for those humans from sub-Saharan Africa. The evidence for Denisovans is much smaller, limited to a few fingerbones in a cave in central Asia. But Denisovan DNA has been found amongst humans adapted to live in cold climates. The “hobbits” (pictured here) may have coexisted alongsid humans until just ten thousand years ago. What killed off our competitors? We did, obviously, whether through outright homicide, through out-competing them or through disease. In the case of the Neanderthals and Denisovans, there was also inter-breeding.
When the Great Leap forward begins, humans can be found in Africa and Asia. By 15,000 years ago, humans had spread to every continent except Antarctica. When humans arrived in Australia and the Americans, the large animals that had thrived there for millions of years (like the giant American armadillo, the glyptodont, pictured here) soon vanished. Human hunting played a big role in their extinction and this points to a quantum leap forward in human hunting efficiency after the development of language and composite tools. Why didn’t the large African mammals vanish? They had evolved alongside of humans and had developed a basic wariness where humans where concerned – a fear not shared by their American and Australian counterparts.
Hunter-gatherer societies are those in which the men engage in high-risk hunting while the women focus on the low-risk gathering of fruits, nuts and other foods. Hunter-gatherer bands are based on the family unit and tend to be matriarchal. Private property is practically nonexistent, everything is shared and decisions are made, as needed, by a family elder or elders. ALL human societies were of this basic type in 11,000 BCE. No one region or group had advantages over any other group. If there is a “starting line” for human history, this is it.
Hunter-gatherers are constantly on the move, seeking or following major food sources (think of the Plains Indians following the herds of buffalo). About 9000 BCE, hunter-gatherers in Southwest Asia began to stay out, and focus on the regular planting of crops native to the region, like wheat, barley, oats and peas. They began to domesticate animals like cows and goats instead of hunting them. About this time, Eurasian people begin to become tolerant of milk digestion – an adaptation very advantageous to people who now have access to cow and goat milk. Such an adaptation may have appeared tandonly, but given its huge adaptive value, it was quickly selected for and became widespread.
Different regions adopted agriculture at different times, based on how easy it was to domesticate the native plants. The Americans had the toughest job in that corn was notoriously difficult to turn into a reliable food source. The root stock of corn, teosinte, only yields a couple of stubby grains. The southwest Asians had the easiest job – wheat, barley, oats and peas are even in their natural state, easy to cultivate. This head start on agriculture gave an advantage in development to the southwest Asians – an early lead in the race to wealth, technology and power that persists to this day. Which makes sense, given that Europeans have had a 2,000 year head start on Asia – and a 6,000 year head start versus Native Americans.
Agriculture and domestication of animals created a positive feedback loop for human populations. More calories means more people and more people leads to a greater demand for food which results in more food being produced which leads to still more babies… and – well, you get the picture. Human groups grow past the hundred-person or so maximum found in hunter-gatherer tribes. New social structures and new customs are needed to cope with the population increases. The first governments begin to appear as large groups need to find some better way of coordinating activities and distributing resources than simply letting custom and family elders call the shots. It is this increase in population that leads us towards a recognizable civilization.
We often associate the adoption of agriculture as if it were invented, like the telephone. But hunter-gathers have always engaged in some agriculture. They would plant seeds, move on to the next food source and then return, to harvest whatever grew. Those tribes that had the most success with agriculture had the most surplus food – and the most population growth. More people required more food which meant more planting. Eventually, a tipping piint is reached where the food needs are so great they can only be met through continuous planting. In such a manner did hunter-gather tribes transition from hunting, gathering and migration to settled agriculture. Such a gradual process is autocatalytic or self-starting. Once it begins, the positive feedback loop thus created will generate the final outcome.
Those that adopted permanent settlements and agriculture first had a head start over other cultures in other regions. Much of the disparity in wealth even today can be traced back to the early advantages conferred by an early adoption of agriculture. Agriculture increases population. Extra people allows for specialization – now, some community members can do other things besides look for food. Art, sciences, technology, commerce, organized religion, organized government all become possible. These early advantages build on one another. Now we have a planet full of unequal societies.
Çatalhöyük, pictured here, is a large Neolithic settlement in central Turkey that represents this transitional period from hunter-gatherers to settled, city life. Çatalhöyük flourished about 7000 BCE and is interesting in that the buildings are grouped closely together, without any hierarchy (no one house is much bigger or better than the others). Access was via rooftop, not by side doors. At this point, agriculture is making huge population densities possible and those extra people can now engage in specialization. Specialization leads to hierarchies, to priests and kings but the evidence of Çatalhöyük is that humans in southwest Asia clung to older, hunter-gatherer ideas of equality even after population densities allowed for towns and cities. The final step in this process will be the development of writing in southwest Asia about 4,000 BCE and the beginnings of recorded history.
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