Preface. The human brain and culture evolved at an astonishing rate, making scientists wonder what conditions and ecological pressures drove it, why we became homo sapiens so quickly. This is a post that will grow over time as I find new reasons and go back over my other research to assemble existing theories. So far I summarize bipedalism and have a book review of “The 10,000 Year Explosion. How Civilization Accelerated Human Evolution”. But there’s climate change, our opposable thumb making it possible to manipulate objects well, fire, increasing eusociality, and more.

If you read my posts on Rare Earth (here and here): why complex life is rare in the universe, you will be even more amazed we evolved at all, and may even convince you we could be the only intelligent life in our galaxy (and many others). Few planets are likely to even have complex life, since multi-cellular creatures only evolved ONCE in the 5 billion years planet Earth has existed.

So it would be a tragedy if we drive ourselves and millions of other creatures extinct or nearly so through nuclear war, pollution, and the other boundaries we must not cross:  Rockström J (2009) Planetary Boundaries: Exploring the Safe Operating Space for Humanity. Ecology & Society 14(2):32. Climate change is not the only problem folks!

Alice Friedemann  www.energyskeptic.com  Author of Life After Fossil Fuels: A Reality Check on Alternative Energy; When Trucks Stop Running: Energy and the Future of Transportation”, Barriers to Making Algal Biofuels, & “Crunch! Whole Grain Artisan Chips and Crackers”.  Women in ecology  Podcasts: WGBH, Jore, Planet: Critical, Crazy Town, Collapse Chronicles, Derrick Jensen, Practical Prepping, Kunstler 253 &278, Peak Prosperity,  Index of best energyskeptic posts

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Bipedalism

Over a lifetime, the average person will take around 150 million steps—enough to circle Earth three times. We still do not know why upright walking was advantageous for our earliest ancestors and extinct relatives, it could be more for more than one reason. Here are a few:

• To see over tall grass to spot food and predators
• Walking on two legs freed the hands to use tools and gather food
• Wade through shallow water to evade predators and gather shellfish
• A more energy efficient way to travel so more energy to raise children
• A better way to move on the ground when we came down from the trees
• Thermoregulation of body heat since walking upright reduces direct sunlight from above, and increasing air-flow across the body
• Mothers needing to carry their babies and consequently inventing the first tools: bags to carry the baby and gathered food (mushrooms, plants, grubs, tubers and more).
• As a consequence of a better diet from better foraging with nets and later tools/weapons, a larger brain could be supported, leading to more and better food, leading to more brain development…
• Though bipedalism may have happened before tools, and enabled them

Sense of order

Remembering the order of information is central for a person when participating in conversations, planning everyday life, or undergoing an education. A new study, published in the journal PLoS ONE, shows that this ability is probably human unique. Even the closest relatives of humans, such as bonobos, do not learn order in the same way.

“The study contributes another piece of the puzzle to the question of how the mental abilities of humans and other animals differ, and why only humans speak languages, plan space travel, and have learned to exploit the earth so efficiently that we now pose a serious threat to countless other life forms,” says Johan Lind, associate professor in ethology and deputy director at the Center for Cultural Evolution, Stockholm University.

Earlier research at Stockholm University has suggested that only humans have the ability to recognize and remember so-called sequential information, and that this ability is a fundamental building block underlying unique human cultural abilities. But previously, this sequence memory-hypothesis has not been tested in humans’ closest relatives, the great apes. The new experiments show that bonobos, one of the great apes, struggle to learn the order of stimuli.

Johan Lind et al, A test of memory for stimulus sequences in great apes, PLoS ONE (2023). dx.plos.org/10.1371/journal.pone.0290546

https://phys.org/news/2023-09-distinguishes-humans-animals.html

Getting in touch with your inner Neanderthal: a book review of Gregory Cochran and Henry Harpending. 2009. “The 10,000 Year Explosion. How Civilization Accelerated Human Evolution”. 

This book makes the astounding claim that our evolution has sped up 100 times faster in the past 10,000 years than the previous six million years.  Even people 4,000 years ago were genetically and culturally different from us.

How do we know this? One way is from looking at both human and chimpanzee DNA.  We know we split off from chimps about 6 million years ago, so we can compare the genetic differences and thus the long-term rate of genetic change.  The rate of change the past few thousand years is 100 times greater than the long-term rate over the past few million years.  If we’d always evolved at such a fast rate, the difference between chimp and human DNA would be much greater than it is.

If evolution this fast seems impossible, then consider how different dogs are from wolves.  It took less than 15,000 years to go from wolf to a Chihuahua. There’s no other mammal on earth with more varied forms and sizes than dogs.  Dogs also vary widely in behavior.  For example, some can learn much quicker than others.  Border collies just need 5 repetitions of a new command to learn it and follow the command correctly 95% of the time, but a basset hound will need 80 to 100 repetitions and only obey correctly 25% of the time.

And it isn’t just a dogs appearance, dogs are much better at understanding our commands and gestures than wolves are.

Russian scientist Dmitri Belyaev created a domestic fox in just 40 years by selecting the most tame foxes in each generation.

As far as humans go, it’s pretty obvious evolution has taken place the past 50,000 years – just look at all the varieties of skin, eye, and hair color. Such skin-deep appearances were all we could see until recently, but with genetic testing we can see more than superficial differences – we also vary in bones, liver and brain function, disease resistance, etc from each other quite a bit.  All of us can speak and have evolved better hearing as well to understand complex language and perhaps to better eavesdrop.

For a long time scientists have been baffled about why humans made a very sudden shift about 50,000 years ago – suddenly advanced, complex art, culture, tools, and weapons came on the scene.   For several decades now scientists have been trying to understand what happened.

This is different from the overall “prime mover” – of why we are the way we are.  Recent evidence supports the thermal hypothesis, other proposals include Man the Hunter, tool making, speech, social intelligence, taming fire, a constantly changing climate, etc and most likely of all, a synergy of these and many factors not listed as Peter Corning explains so well in “Nature’s Magic”.

Once our amazing culture evolved, we were no longer bound by natural selection – we didn’t need to evolve fur when we moved into colder climates, because we could make warm clothes, and we didn’t need to evolve strong muscles to hunt large animals – we could build better weapons.

And once we had better weapons, such as the long distance spear throwing atlatl, humans didn’t have to be muscular heavy hulks risking their lives every time they hunted.  We became smaller, needed less food, and perhaps that’s why we out-competed Neanderthals.

my comment: I don’t believe that research has borne this out, but the book says, FYI:

But how could we have evolved so rapidly 50,000 years ago? Here’s the bombshell theory – we interbred with Neanderthals! The authors explain that a common misconception is that people think that Neanderthals were closer to apes than people, but that is not at all true.   They also had large brains, speech, and cooperated highly with each other when they hunted together. We had too small a population to have enough mutations to evolve quickly, the only way it makes sense for this sudden change to have happened is for us to have acquired useful genes from Neanderthals.  All it would have take is for a few dozen half human – half-Neanderthal babies over thousands of years for us to gain their best genetic strengths.

Ultimately, the most important result of our recent evolution was our ability to innovate.  Every new innovation led to new selective pressures, which caused us to evolve in new ways.  The most important innovation, and the one that caused the most evolution the past 10,000 years, was the invention of agriculture.

Once we had agriculture, the human population grew enormously, which meant a much larger pool of potentially beneficial mutations happening – 100 times more than in the Pleistocene.

Agriculture also created diets early farmers weren’t adapted to.  They ate way more carbohydrates and less protein, didn’t get all the vitamins they needed, and lived much shorter and unhealthier lives.

But mutations arose that changed that.  Here’s just one example (that you may know): About 8,000 years ago the ability to drink milk as an adult arose in Europe, and now about 95% of people in Denmark and Sweden have no problems with digesting dairy products, and 80% of the rest of Europeans, on average.  A different mutation that did the same thing arose in East Africa, and now 90% of the Tutsi are lactose tolerant.  Densely populated areas evolved disease resistance, the ability to drink alcohol, and many other non-skin-deep abilities that we can now “see” with genetic studies.

At times in the Old World, when war wasn’t the main source of deaths, famine and malnutrition limited populations that reached carrying capacity.  The poorest were so short on food that they didn’t reproduce themselves, while the elite had more than the two children required to replace themselves and had twice the number of surviving offspring as the poor.  The least successful rich children became the new farmers, with the result that after a thousand years or so, everyone was descended from the wealthy classes.

Once the ruling elites existed, they didn’t have a hard time controlling farmers, who couldn’t leave their land in protest, or they’d die, which stuck them with paying whatever taxes, being conscripted into wars and in general endure whatever the elites dished out.

The authors suggest that in the end, people were ultimately domesticated by elite rulers, who weeded out aggressive fighting peasants, just as farmers weed out their most aggressive animals.  The elites selected for a population that submitted to authority. Attention deficit disorder doesn’t exist in China – the elites completely bred that behavior out of the population.  I found the whole idea fascinating and scary, the full discussion is on pages 110-113.  Maybe that explains why Americans have allowed the greatest disparity in wealth between rich and poor in our nation’s history to exist, haven’t marched with torches and pitchforks on Wall Street, and so on.

A chapter of the book is devoted to why Ashkenazi Jews are so much brighter than other populations.  Although they comprise less than one in 600 people, they’ve won one in four of all Nobel science and too many other achievements to list here.   Basically the hypothesis is that because they were forced to hold difficult white collar jobs for centuries in finance and related areas, and couldn’t marry outside their group, evolution selected for intelligence.  Unfortunately, this selection comes with genetic disorders of Tay Sachs and other diseases.