1. Climate Change and the Big Giant Head

Today, we are learning firsthand the impact of climate change on life. It can trigger both mass extinction and evolution depending on a species ability to adapt to it. Climate change millions of years ago in East Africa is now thought to have been responsible for the evolutionary strides made by our distant ancestors. Then, East Africa was covered with humid forests and we were pretty content as knuckle-walking tree dwellers that lived in the canopy and succeeded in avoiding being made a meal by just about every predator around. But that forest was destined to change to arid savannah. Groves of trees became islands surrounded by undulating seas of grassland and hominidae had to rethink their food strategy or succumb to extinction. Sound familiar? Major events include Cretaceous Paleogene extinction event 65.5 million years ago and the Paleocene Eocene Thermal Maximum 55 million years ago. Our ancestors managed to survive, thanks to bipedalism undoubtedly triggered by the creation of those early savannahs.

Bipedalism made it possible to move efficiently from one tree island to another. Standing erect gave us a far more complex view of distances and the predators hoping to make a meal of us lurking in the grass. The gained efficiency in locomotion not only allowed us to run like hell if we had to, we could cover far more territory, and by doing so expand the our resources exponentially. Free hands allowed us to carry tools and infants. With handedness we found ourselves picking up objects that could be used as both tools and weapons. We quickly became proficient at killing small animals, cracking nuts, butchering carcasses, and carrying the bounty back to group members for sharing. Standing on two feet allowed us to reach foods previously inaccessible. Over the course of millions of years skeletal changes evolved that included legs, hips, vertebral column, feet, ankles, and of course the skull. The vast improvement and diversity of nutrition coupled to the epiphany of tools is convincingly linked to bipedalism and set the stage for developing a big and very hungry brain.

Even greater strides were made with more recent climate change events. In the last 3 million years there have been persistent cycles of glacials and interglacials (the growth and retreat of ice sheets especially in the Northern Hemisphere) with fluctuations of 40,000 to 100,000 years. These are believed driven by predictable changes in the Earth’s orbit, and the rise and fall of atmospheric carbon. The rise and movement of tectonic plates changed ocean currents, the distribution of heat, and altered atmospheric patterns 2.8, 1.7, and 1.0 million years ago. These dates correlate to big evolutionary leaps by our distant relatives.  This is commonly referred to as the Quaternary sub-era that began in the late Neogene period and continues today.

So let’s take a look at that big brain of ours. Its evolution is called encephalization and its sophistication is measured by the ratio of the brain’s mass to the rest of the body.  The human brain is more than twice the mass ratio of that found in chimpanzees and gorillas. An acceleration of brain growth and differentiation took off with Homo gauntengensis, Homo habilis, and Homo erectus. I’ll take a closer look at each of these ancestors later on. The increase in brain volume however was disproportionate. For example the temporal lobes increased due to language development and processing; the prefrontal cortex evolved allowing more and more complex decision making and moderating social behavior. Intelligence increased due to the necessary problem solving as society became more complex. Although the size of Neanderthal’s brain was actually bigger than ours it apparently had neither the complexity nor the subtle nuances our brains today have cultivated.

Encephalization is tied to eating more meat and the development of cooking. Big brains demanded energy rich food and undoubtedly triggered the escalation of tool technology. Tools in turn led to vastly more sophisticated hunting techniques to acquire energy rich meat and process more energy rich plants. Until about 50,000 years ago tools developed in steps. Each phase was higher than the previous phase but little development was demonstrated during the phases themselves. Then the phases turned into multi-platform leaps. Homo sapiens, 50,000 years ago began burying their dead and including grave goods and offerings in those burials. Tools and hunting techniques advanced inordinately with complex specialization. Items such as fish hooks, needles, and button showed up in some locations. Living space became organized, the concept of ritual began, and wondrous things like jewelry and cave painting commenced. Exploration of previously unknown regions began and led to trade networks. With some dismay it should be mentioned too that the ideas of trapping pits and running herds over cliffs also started to occur. It should be noted that not all of science embraces the 50,000 year mark; some believe the process was far more gradual. But either way from here we can see the unfortunate demise of our Neanderthal relatives whose tool technology did not advance even though Neanderthal and Sapiens lived side by side for many millennia.

About 350,000 years ago Neanderthal colonized Europe and the Middle East.  About 200,000 years ago Homo sapiens appeared in East Africa. Eighty to 100 thousand years ago three main branches of Homo sapiens diverged and the Great Leap Forward, as it is sometimes called, took place shortly thereafter marked by its increase and sophistication of tool making. Homo sapiens migrated out of Africa about 60,000 years ago at the end of the Middle Paleolithic and met his Neanderthal relatives for the first time perhaps 40,000 years ago. Neanderthal lived in the cold and he needed enormous amounts of fat and protein. He was a skilled hunter and there is no evidence that suggests he was a scavenger. But skeletal fractures, similar to those seen in rodeo clowns, suggest that hunting for Neanderthal was a dangerous affair, making some believe he often leapt on his prey and wrestled it to the ground. Fossil evidence shows that he suffered from degenerative diseases associated with over use. Although Neanderthal’s reign had been long and successful his failure to evolve parallel to Homo sapiens led to his extinction about 24,000 years ago even though for 190,000 years Homo sapiens led a similar life style consuming wild game, fruits, vegetables, and nuts. It should be noted that these dates are by no means set in stone and controversy about them continues.

Bipedalism, tool making, and encephalization with its nutritional demands, in my view, can’t so easily be compartmentalized. It is likely that our Hominidae relatives, the Great Apes, gave us cognition and empathy from the very beginning. The retreat of the forest 10 to 2.6 million years ago forced our later Homininae relatives to the ground. Seven to 5 million years ago bipedal, tool- using primates showed up in the Hominina sub tribe of Sahelanthropus. Rapid brain development, size, and differentiation took off from there and the distinction between humans and other primates began to show. Great apes aren’t particularly cooperative or communicative. They are highly competitive by nature sporting big canines used as a visible threat. Early Hominins were smaller and had smaller canines which might have been a factor in developing superior cooperation and communication, while abandoning the need to threaten others in their group with large, dangerous teeth. When the genus Homo emerged about 2.4 million years ago the advancement of tool technology indicates he had a large and sophisticated brain with the manual dexterity to accomplished subtle and complex hand movements. Our brains continued to increase in size, complexity, and differentiation.

But those big fat heads came with a price. The needed changes necessary in the birth canal would have led to a pelvis so wide a female would have lost her ability to run, no small thing in a world of predators looking to have a meal of genus Homo. The alternative, a successful one, was to give birth much earlier. This is thought to have led to social changes because females had to care for helpless infants and their bands tended to stay in one place longer so that that care could be rendered. It was probably a big factor in division of gender roles, becoming necessary for males to do most of the hunting. Protecting females and infants took on a new imperative for males as well. Tool technology now had to include greater and greater defense.

All of this leads us to a closer scrutiny of the brain’s nutritional appetites. Our brain requires 16 times more energy than muscle tissue per unit of weight. At rest the human brain metabolism accounts for 20 to 25 % of adult energy needs as compared to 8-10% of non-human primates and 3-5% by other mammals. Encephalization simply couldn’t have occurred until Hominins adopted a diet rich in calories and nutrients to meet the associated costs; big brains require energy dense food. According to Sobieraj the nutrient density of 3.5 ounces of meat measures at about 200 kilocalories as compared to fruit of an equal weight at 50-100 kilocalories and foliage at 10-20.  The cold of ice ages required an increase of dense calories of 15-25%.

It has been my contention that the issue of cold and calories plays important role in today’s obesity. Genes from cold climate ancestors carry the demand to eat more than can be burned in warmer climates. Perhaps if the challenge was met with the knowledge of a specific person’s genetic makeup, diets could be designed along the lines of their ancestors’ diets. Although I am not suggesting in any way that this is the only factor, I do believe genetics play an important role in solving the problem. For example, I doubt that Scandinavian people do well consuming a typical Mediterranean diet simply because enough time hasn’t passed to have effectively adapted to it nor does it address the nutritional needs of a people living in a cold climate. Sobieraj points out that the Siberian reindeer people, the Evenki, derive almost half their calories from meat, 2.5 times more than Americans. Yet the Evenki are 20% leaner with cholesterol rates 30% lower because the animals they eat are free range and leaner. While the Evenki derive 20% of their energy from fat, Americans consume a whopping 35% in fat.

This leads me to place an even greater importance on the seasonal rotation of foods similar to hunter-gatherer diets. Clearly the maximum amount of meat needs to be eaten in the dead of winter followed by a spring detox of cool weather herbs and leafy vegetables. By early summer a transition to berries makes enormous ecological sense, supplemented by fish. Late summer and fall bring nuts, roots, and grains into the picture beside late ripening fruit before transitioning back to the dense protein found in meat needed in cold weather.

The evolution of teeth and jaws lends some insight. Australopithecus was designed to consume predominately tough fibrous plant food even though fossil evidence shows he was an omnivore, possibly initiating the shift of hominid diet to an increase in protein consumption. Virtually all primates are in fact omnivores. Orangutans eat fruit and roots but also consume insects, small vertebrates, bark, and eggs. Gorillas love vines and leaves, water plants, stems and pith, wood, roots, flowers, fruits, and grubs. Chimpanzees and bonobos eat a high percentage of termites with their vegetarian fare as well as monkeys, pigs, and antelope. As a matter of fact chimpanzees were the first to demonstrate organized hunting and meat eating in hominids.

Early Homo’s facial anatomy was designed for more animal and less plant food.  Expansion into Europe by Homo erectus was probably nutrition driven. His facial anatomy and advanced hunting tools suggest an even higher consumption of meat. The increase in meat consumption necessitated an 8-10 fold increase of his hunting range over that of Australopithecus. Migrating herds probably led the way. Homo erectus was most likely a scavenger as well. It has been proposed that an increase in meat in our diet required that our guts reduce in size and complexity to accommodate our brain’s demand for more protein.

The changes that led to African savannahs meant more game animals and less edible plants and bipedalism permitted exploitation of these animals. The first evidence of hunter-gatherer economy appeared where game animals were shared with the group. Numerous sites have been found with increased animal bones and evidence that the animals were butchered with tools. “These changes in diet and foraging behavior did not turn our ancestors into strict carnivores; however, the addition of modest amounts of animal foods to the menu, combined with sharing resources that is typical of hunter-gatherer groups, would have significantly increased the quality and stability of hominid diets. Improved dietary quality alone can’t explain why hominid brains grew, but it appears to have played a critical role in enabling that change. After the initial spurt in brain growth, diet and brain expansion probably interacted synergistically; bigger brains produced more complex social behavior, which led to further shifts in foraging tactics and improved diet, which in turn fostered additional brain evolution.” The control of fire and cooking food followed, allowing for improved availability of plant nutrients from wild plants and perhaps an increase in the diversity of animals species eaten.

http://people.bu.edu/sobieraj/EvolutionNutrition.html




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