A million years ago, our Homo erectus ancestors consisted of maybe 20,000 breeding individuals, according to wizards who speculate on the hidden secrets of DNA. This is similar to the current population of chimpanzees or gorillas. The ancestors lived in scattered pockets of Africa, at a time when Earth was a paradise of abundant life. From these ancient roots, a number of hominid species evolved, but only Homo sapiens still survives, at seven-point-something billion and growing. The chimps and gorillas continue to live in a manner similar to their ancestors of a million years ago. What happened to us?
Chris Stringer is one of the venerable grandfathers in the study of human evolution. He’s read the papers, attended the conferences, examined the skulls, and had a ringside seat at the noisy catfights. This field of knowledge is far from finished. New specimens continue to be found, and new technology provides deeper insights. Stringer’s book, Lone Survivors, discusses some primary issues, and the scholarly disputes surrounding them, as they stood in 2012. He does a pretty good job of providing an overview to a huge and complex subject, but readers with little background are advised to wear life preservers.
I learned a lot about Neanderthals. They survived 400,000 years on a climate change roller coaster. They hung out with hippos in warm forests near Rome, and they chased wooly mammoths on frigid treeless tundras. They had short, stocky bodies that were good for preserving heat, but which required more calories. Males and females were about the same size, suggesting little division of labor, everyone joined in the hunt.
The Neanderthal diet majored in the flesh of large game. Readers who have hunted hippos with wooden thrusting spears know that his is very dangerous. One site in Croatia contained the remains of 75 Neanderthals, and none were older than 35. In their clans, there were probably many orphans and few grandparents. The scarcity of elders, and the small size of their groups, sharply restricted the flow of cultural information from one generation to the next, and from clan to clan.
Some say that Neanderthals lacked shoes and close-fitting clothing. When Darwin visited chilly Tierra del Fuego, at the bottom of South America, he was shocked to see natives wearing little or no clothing and sleeping naked in the open. Stringer noted that modern Europeans seem to be poorly adapted to the cold, physiologically.
Cro-Magnons were the Homo sapiens that moved into Europe maybe 45,000 years ago. European Neanderthals disappeared around 30,000 years ago. Neanderthals went extinct in the Middle East, Siberia, Gibraltar, and Britain at different times, probably for different reasons. This was an era of frequent climate zigzags. When temperatures plummeted, habitable territories shrank, and fewer folks could be fed.
Cro-Magnons apparently had footwear and warm, fitted clothing. They had better tools for hunting, so their diet was more diverse and dependable. They were able to extract more nutrients from an ecosystem, so they could survive in places where Neanderthals could not. They lived in larger groups, and more of them survived to middle age or old age, so more cultural information could be passed to the young.
Large populations are better at preserving cultural knowledge, acquiring new information from outsiders, and generating innovations. More busy minds interact, exchange ideas, compete, and imagine cool ways for living even farther out of balance. Witness the city of Los Angeles, where 14 million animals with hunter-gatherer DNA are temporarily able to survive because of a highly complex system of innovative technology. Note that this innovation has no relationship to foresight or wisdom. Time is running out on Los Angeles.
On the other hand, less innovation occurs in smaller simpler groups, and that’s often a blessing. Innovators can be dangerous loose cannons, introducing risky new ideas that result in horrid unintended consequences — like cell phones, automobiles, or agriculture. Nothing is more precious than a stable, sustainable, time-proven way of living, where the secret to success is simply imitating your ancestors, conforming to the norm, and enjoying life, like the chimps and gorillas do.
When the planet heated up 14,000 years ago, rising sea levels submerged the land link between Australia and Tasmania, terminating the exchange of people, ideas, and gadgets. Tasmania’s traditional way of life was also squeezed as the warmer climate spurred the expansion of heavy forest. The natives experienced a cultural meltdown. “Tasmanians appear to have led an increasingly simplified life, forgoing apparently valuable skills and technologies, such as bone and hafted tools, nets and spears used to catch fish and small game, spear throwers and boomerangs, and anything but the simplest of skin clothing.”
Will climate change have a similar effect on industrial civilization in the coming decades? Will it slash food production, sharply reduce population, eliminate travel between regions, pull the plug on modern technology, and erase lots of obsolete and unsustainable cultural information? Could collapse have a silver lining?
Climate change can derail any culture, and drive species to extinction. It can also produce beneficial conditions, like the unusually favorable climate of the last 10,000 years. Natural selection rewards species that can adapt to change, and it deletes those that fail. There is another important variable that is often overlooked — genetic drift — mutations that happen all the time when slight boo-boos occur during cell division. These tiny defects can provide a barrel of surprises.
We are repeatedly taught that humans are nature’s flawless masterpiece, the glorious conclusion of three billion years of evolution. But, if Big Mama Nature had experienced slightly different moods over the eons, we might be Neanderthals or Denisovans today (or maybe slime mold). Climate change and genetic drift are purely random. The fact that Homo sapiens is the lone survivor among the hominid species is not absolute proof of superiority, but it does indicate a temporary streak of good luck.
Homo heidelbergensis was an ancestor that lived 500,000 years ago. They had brains ranging in size from 1100 to 1400 cc (modern brains average 1350 cc). The average Neanderthal brain was 1600 cc — much bigger than ours. Stringer noted that our brains today are ten percent smaller than our Homo sapiens ancestors of 20,000 years ago. Is there a message here?
Without words, chimps and gorillas can express contentment, affection, irritation, excitement. But without complex language, they are more trapped within themselves. Language took us “into new and shared worlds that were unknown to our ancestors.” We can talk about the here and now, the past, the future, abstract concepts, feelings, imaginary worlds, and so on.
Later, innovative geniuses invented the use of symbols. Now we can convert words into patterns of squiggly lines, for example: “computer.” Writing enables us to communicate with folks in faraway places. I can read words written by Julius Caesar, and so might the generations yet-to-be-born, in theory. Industrial civilization cannot exist without symbols — numbers, graphs, pictures, status symbols. Progress abounds with powerful and dangerous juju.
Stringer is a mild mannered humanist. And so, he portrays the human journey as one of admirable advancement (the chimps fall down laughing). On the last page, he confesses a profound doubt. “Sometimes the difference between failure and success in evolution is a narrow one, and we are certainly on a knife edge now as we confront an overpopulated planet and the prospect of global climate change on a scale that humans have never faced before. Let’s hope our species is up to the challenge.”
Stringer, Chris, Lone Survivors: How We Came to Be the Only Humans on Earth, Times Books, New York, 2012.