Stage #7 200,000—70,000 years ago The Cognitive Revolution Species: Homo neanderthalensis, Homo floresiensis, Homo sapiens The above species emerged around 200,000 years ago and over the course of the following 130,000 years, the species continue adapting to their environments; the most significant of these adaptations was the enlargement of the neural capacity and cultural capacity of Homo sapiens. This advancement culminated with the emergence of language 70,000 years ago. The most significant advancement that came out of this era was cooperation. Homo sapiens began living in larger groups, and staying part of these groups for long periods of time. Descendants of the groups continued to keep the group together in ways that Neanderthals and previous hominids did not. This group bonding laid the groundwork to allow Stage 8: the Cultural Revolution. The one significant physical difference between Homo sapiens and the other species is brain size and facial structures. Body size and shape is strikingly similar in all the hominid species after Homo erectus, other than Homo floresiensis who are known as the Hobbit humans as they stood under 3.5 feet tall. Sapiens’ larger brains allowed them to live and function well in groups nearing 150 individuals. Robin Dunbar of Oxford University has studied group size extensively, especially related to brain size. As brain size goes up, the size of bond groups goes up in parallel numbers. The largest number of individuals with whom an individual in a species can bond is known as its Dunbar number in his honor. 150 is the number for humans; 75-120 would have been near the Neanderthal number. Shortly after the emergence of Homo sapiens, groups started trekking into Europe and Asia. Despite the social differences, sometimes a Neanderthal or Denisovian Juliet would have a tryst with a Sapiens Romeo, and offspring would ensue. In fact we are descended from some of these babies. Humans of European descent have around 11% Neanderthal DNA. Humans of Asian descent have around 8-10% Denisovian DNA. The only humans with 100% Homo sapiens DNA are those of African descent, which is interesting when contemplating the eugenics movements of the mid-20th century during which time many incorrectly said that Northern Europeans were the most pure humans and that Africans were the least. The fact that we share some DNA with our Homo cousins shows that we were close enough to be considered the same species but different enough that skeletal remains can easily be identified as Sapien or Neanderthal. This is similar to a Labrador versus a Great Dane; they’re technically part of the same species, but they are very distinct and without human intervention would be considered different species. It also shows that bands of each species inhabited similar areas for extended periods of time. There is not a significant amount of archeological evidence that shows the tribes warred with each other. So what led to the decline in Neanderthals and Denisovians? Since these groups filled a similar niche, hunter gatherer, they competed for the same resources and Homo sapiens outcompeted the Neanderthals and Denisovians due having more ingenuity and larger groups. Pressures for cooperation and empathy would have expanded in this era of Homo sapiens development because as groups continued to increase, the need to understand social complexities also increased. If you couldn’t get along and pull your weight, you were kicked out, and died in the elements from not acquiring food or you were eaten. Group size increased because the smaller groups could not acquire resources with the same proficiency as the larger groups, and this continued the cycle of pressures selecting for larger brains and specific brain regions. The pressure on empathy and cooperation led to an increase in serotonin and oxytocin levels. The increase in these hormones led to different physical characteristics. These hormones had been being selected for since humans started cooperating, and their increase led to several of the physical changes we see in the fossil record. Increased levels led to permanent juvenile stages. When domesticating any animal, what is truly being selected for are these opioid hormones. They make you happy and less aggressive, which is important if you want cooperation to work or for your dog or cow to not attack you. The increased amount of hormones also influences physical development resulting in smaller physical features. The increasing levels of opioids also led to our ability to reproduce prodigiously as opposed to our chimpanzee cousins who go through 3-5 year stages after birth during which time they cannot get pregnant again. Because humans could and did get pregnant every year, bands grew in size and cooperation again had to increase because human mothers face a challenge no other species does; nursing a child while still having one or more others fully dependent for survival. Because Homo sapiens experienced the greatest pressure on group size and the resulting increase in opioid levels, they were smaller than Neanderthals and had less pronounced brows and cheekbones. However, they had not yet reached modern levels because they had not experienced the full selective pressures of domestication; these would not come about until the agricultural revolution. This means ancient humans were larger than modern humans with more pronounced brows and cheeks. Stage #8 70,000— 13,000 years ago. The Cultural Revolution Homo neanderthalensis, Homo floresiensis, Homo sapiens Following the above “cognitive revolution”, Homo sapiens spread out of Africa into southern Asia and north into Europe. They reach Australia around 45,000 years ago. By 30,000 years ago, Homo sapiens had outcompeted Homo neanderthalensis in Europe to the point that they went extinct. Prior to this, Homo sapiens had outcompeted the Denisovians in Asia. By 13,000 years ago, Homo floresiensis was also extinct leaving Homo sapiens as the lone hominid species left on Earth. So what made Homo sapiens the ultimate Homo species? Cooperation in large groups that led to the beginning of human culture. As humans relied more heavily on living in consistent groups, they were able to pass on knowledge. The first signs of fictive language emerge around 70,000 years ago. Fiction provided a basis for keeping a group together and ensuring cooperation. If a group believes in a common myth, they will share a special bond akin to the bond that family members share. This is still true today in how religions and professional sports teams can bond complete strangers in very strong ways. Furthermore, storytelling would have allowed knowledge gained by one generation to be passed on to the next. This meant that any significant discovery in one generation could be used and improved upon by the next; this trend also continues today, and has allowed the many scientific discoveries we are used to and take for granted. Humans did not change in appearance that much throughout this time period, but as different bands colonized different areas of the globe, they began evolving to their environments and the current races of humans are the result of the last 50,000 years of evolution. Europeans mutated to deal with the lack of sunlight in the northern climates by producing less skin pigment, which allowed more penetration of UV light in winter months generating greater amounts of Vitamin D and other regulatory proteins. Inuit people evolved to the extreme colds of Arctic climates by having a lower average body temperature. Kenyans evolved to the high mountainous regions by increasing VO2 max and shifting muscle locations to make running even more efficient. Stage #9 13,000—200 years ago Homo sapiens With the rise of cultures and religions, people started placing importance on certain areas and landmarks. With the rise of these landmarks, people began frequenting the area and staying closer. This was the first steps away from hunting-gathering and toward agriculture. As these people stayed in a certain area, they became more familiar with the plants that grew in the area. This led to cultivation as some groups found that they could take seeds from one area and plant them in another. Depending on the area, groups cultivated different grains that grew best. Today, around 90% of our calories come from plants domesticated between 11,500-3500 years ago. Evidence for this can be found in archeological sites such as Gobekli Tepe that date back to around 11,500 years ago. This temple was built by hunter gathers, but ancient wheat grains dating to before 11,500 years ago are found buried at the site. Archeologists infer that as hunter gathers made treks to the temple at certain times each year, they planted wheat seeds and then harvested when they returned. Over time, certain populations stayed near these sites and continued to become more reliant upon crops. By 10,000 years ago, many such villages had sprung up, and their remains can still be found at sites all around the Middle East. Early farmers would have still relied upon hunting and gathering, but eventually they became more and more reliant upon the crops they grew. At first, they would not have spent that much time with cultivation, but as they discovered little improvements like the deeper you plant seeds, the better they grow, and when you pluck weeds from the rows, they grow better still, they came to spend more and more time working the land and less time hunting and gathering. These initial tradeoffs, added up to significant costs over time. The initial compromises to grow better crops would have been negligible, a couple extra hours to use a rock or stick to tear up the ground and put the seeds in, and then just a little more time to ensure that other plants don’t interfere. After several thousand years of small concessions, though, they had to spend so much time in the fields they became fully reliant upon their crops for survival. In the good years, the crops produced excess food that could be stored. However, the crops did not provide as varied a diet as the hunter gatherer diet. This led to malnourishment and disease, and higher infant mortality. Remains reveal that about 1/3 of children died before age 20. Furthermore, farming was a lot harder work than hunting and gathering. By 10,000BC, humans had become proficient hunters with bows and arrows and spears and culture meant that they were good at finding and obtaining nutrient dense fruits and vegetables. Thus, people living in 8,000BC Jericho lived harder, sicker lives than their ancestors who lived 2,000 years earlier. The excess also led to increased fighting amongst tribes over resources. The evidence for this is also found in the remains of individuals from this time. Bones found near farming communities from this time show a marked increase in healed broken bones (this doesn’t make sense if you’re farming, it only makes sense if you were attacked by other farmers) and lethal skull fractures made by stone hammers. The other change that agriculture brought about was an increase in tribal size. Group work caused increased yields and more people to be able to live in a given area. This increased disease and malnutrition as well. Diseases found perfect incubators in the humans and began mutating and becoming more lethal. Some diseases were able to wipe out entire villages. Unfortunately for these ancestors, we had not evolved to be bent over plucking rocks and weeds for hours at a time, and this led to increased spinal disorders and resulting deaths. Our ancestors were also not evolved to subsist on only grain. Today, some people still have problems digesting certain grains like wheat (gluten intolerant), corn, rice, and barley. We need certain enzymes to be able to digest and get nutrients out of these grains. If our early ancestors didn’t have any precursors to these enzymes, they would have starved or died of an allergic reaction. The first farmers did not have an easy go of things. Our digestive systems today bear the traces of this evolution since most of us can digest grains, lactose, and other cultivated foods not available to hunter-gatherers. Furthermore, humans having to live in even larger groups put even greater pressures on social intelligence and thus we are all, for the most part, good at navigating social situations. The brain regions that allow us to do this are some of the largest regions we have with the highest number of neural connections. Stage #10 200 years ago— present Industrial Revolution Homo sapiens The final stage of human evolution is still currently under way. 200 years ago, industrialization took off and the fruits of the agricultural revolution were finally harvested…perhaps…The agricultural revolution allowed cities to form and caused the creation of writing to keep track of harvests and taxes; writing also allowed ideas to transcend generations. This allowed people hundreds of years after the writer to continue forming and perfecting ideas. The results of this were the inventions of the past 200 years that have made life infinitely easier for many humans in Western cultures. However, do not be fooled because we also have more diseases and widespread suffering than was present prior to the agricultural revolution. In the last 200 years, the world’s population of humans has increased by over 7 billion. The invention of new technology that has made agriculture more efficient and advances in health care has allowed this to take place. The result of this is that the normal pressures of evolution have been stalled in humans. Because women no longer die in childbirth with as much frequency, some genes for poor uterine wall formation have been able to stay in the gene pool. Other genes that would have been whittled out of the gene pool: myopia (bad eyes), allergies to certain foods, hypertension (high blood pressure), bad cholesterol and a slew of others remain. The fact that modern medicine has allowed these people to survive is good for the people with the ailments, but it means that the bad traits are passed on to the offspring who will have similar problems, and looking into the future, the genes will continue to become more prevalent because they are not being eliminated. Our ancestors shared the world with many people who had traits that made them unsuccessful at surviving and reproducing. Because these people died off before reproducing, we did not inherit their defects. If we look forward to 1,000 years from now, our descendants will have more illnesses because the susceptibility to the illnesses was not cut out of the gene pool. The world, and especially our diet are changing so fast that the averages of evolution cannot keep up. For example, we initially began evolving away from our ape-like ancestors because of climate change. Relatively few would have died each year from lack of food, but, over time, these slightly more common deaths in certain groups added up to the different species. Humans are good at navigating through the quickly changing climate because of our technology, but other animals are not so lucky, and are dying in unnatural droves. Again, remember that evolution happens slowly because while much variation exists within a population, those variations are slight and can only accommodate small changes. Today humans consume foods that have been part of our diet for hundreds of thousands of years, meat and certain vegetables like sweet potatoes. However, most of the food is extremely altered from its original form through the process of hybridization and cultivation. Furthermore, within the last 70 years, completely new additives created in a lab have been added to our foods. We have not evolved the hardware to break down these additives and much of the current health crisis is the result. However, the sheer availability of food has allowed humans on average to grow larger than our ancestors of the recent past as we have excess nutrients available. However, with the invention of genetic engineering and other scientific breakthroughs, we may take over the process of Evolution and make it happen much faster and in unique ways not possible in nature.