Progress Starts With The Imagination

After carving the kneeling angel sculpture, Michelangelo is reputed to have said, "I saw the angel in the marble and carved until I set him free." His words struck a chord. People liked the romantic idea of a sculptor imagining a figure within the stone and then chipping away until he has revealed it. Of course, the reality of how Michelangelo created his masterpieces was more complex, and it involved a lot of hard work and skill.  Nevertheless, the quotation contains a hard fact; creativity and achievement start in the imagination.

Many people believe that it is our imaginative ability that makes us human; it shapes everything we do and create. But we have not always had the imaginative skills we have today. You can see this in the development of stone tools. If you look at any good book about human evolution, it will show the fossil timeline. On the left-hand side are the oldest ape-like fossils, and as you move along the timeline, the fossils become more human. One of the most striking changes over time is brain size. Our early ancestors' brains were less than half the size of those of modern humans. The fossil record does not directly tell us how imaginative our ancestors were. However, we can infer it from the sophistication and quality of the tools they made. Fortunately, stone tools preserve well.  As a result, we can match the fossilized human remains with the tools they made. 

The picture above shows a range of stone tools, from the earliest to the last made at the end of the stone age. On the left side of the timeline is a silhouette of the first deliberately made stone tool. It does not look like much. A hand-sized river pebble with a few flakes removed. If someone had pointed one out to you, you might think that it was just a pebble that had been broken in a natural event. However, paleo-archeologists are confident that early humans deliberately made these tools. Their confidence comes from the discovery of a distinctive wear pattern on nearby rocks. These stones have the sort of pitted surface that results from being repeatedly used as a hammer.  This evidence suggests that early humans used these hammerstones to create the nearby tools.  Archeologists found so many examples in the Olduvai Gorge, Tanzania, that the site gave its name to this type of tool: Oldowan tools. The hominins of Olduvai Gorge got two tools for the price of one. The shards produced could be used for cutting. Also, removing flakes from the core stone gave it sharp edges and provided the toolmaker with a chopper.

The hominins who made the first Oldowan tools probably did so by accident. These apes were not so different from the great apes that are alive today. They certainly did not have the imagination to make good tools.  But, they had just enough vision to recognize how useful a sharp-edged stone and flakes could be.  This insight does not sound like a great accomplishment. However, if you compare it to modern-day chimpanzees or monkeys, you can appreciate its significance. Chimpanzees are clever. Researchers have shown that they can learn sign language and how to make stone tools. However, in the wild, they have never been seen making stone tools.  Like other apes and monkeys, they will use nearby stones to hammer open nuts. However, if a flake splits off the rock, they ignore it. Creating a sharp slicing tool appears to be entirely accidental and of no interest to the chimpanzee. The same is true for the wild capuchin monkeys of northern Brazil. These monkeys have been observed vigorously hitting one rock with another and making things that look like Oldowan tools. However, appearances can be deceptive. Once the capuchins have broken open a rock, they lick it. Then, like the chimpanzees, they ignore the flakes. Researchers think the monkeys are trying to get to minerals inside the rock rather than making tools.

It is difficult to know what factors led to the first hominins deliberately making stone tools. However, it is a good guess that chance played a significant role. About four million years ago, the weather became drier. As a result, the African forests retreated, leaving a patchwork of trees and open savanna.  Some of our ancestors started to move from the forest to the new savanna. Apes like the skeleton of Lucy—Australopithecus afarensis—had adaptations suitable for forest and savannah life. However, they were not well adapted for one or the other. This lack of winning adaptations raises the question, how did they survive? In either environment, they would have been competing with other species that were better adapted. One possibility is that Australopithecus scavenged the large carcasses left by predators like lions. However, a small ape, like Lucy, would have found scavenging dangerous and difficult.  Timing would have been critical. She would not have wanted to be too early or too late. Finding a fresh kill was dangerous. The preditors could still be there. They would defend their kill, and if they were still hungry, a small slow ape would make an easy addition to their meal. However, if Lucy found the carcass too late, it would have putrified in the heat of the savanna sun. The best time for Lucy to scavenge the kill was just after the predators had eaten their fill. However, Lucy would not have been alone; other scavengers would have tried to do the same. Some of these scavengers were almost as dangerous as the predators. Lucy and her kind would have been an easy meal for them.

There might have been a less dangerous way for the first savanna apes to scavenge. Jessica Thompson has suggested they fed on bone marrow. Marrow is a fatty tissue found at the center of bones, such as the hip and thigh bones. Thomspon described it as "like a stick of butter on a landscape where there is no fat."  Every 100 g of marrow contains about 84 g of fat, and fat is the most energy-dense food. Better still, the marrow of large animals is encased in enough bone that even predators like lions cannot get to it and eat it. The only animal with jaws strong enough to get to bone marrow is a hyena.

Another advantage of marrow is that it stays fresh. The bone around it seals the marrow away. Even in the African sun, it will last for days. The additional time makes scavenging much easier. Apes like Lucy had longer to find carcasses, and this would increase their chance of success. If they found a fresh kill, they did not have to risk competing for the meat. They could wait for the predators and other scavengers to finish and leave. Once it was safe, the apes could smash the remaining bones with hammerstones and get to the marrow. Jessica Thompson argues that Australopithecus could have successfully scavenged marrow. This new food source could have created a new evolutionary path. Individuals who could make better tools could get more food energy. Access to more energy would enable them to have more offspring and support the evolution of a larger brain. As brain sized increased, individuals would be able to make better tools and continue the cycle.

By the time you get to the first deliberately made stone tools, you can see that Homo habilis had a noticeably larger brain. A modern chimpanzee's brain is about 400 cc, Lucy (Australopithecus) had a brain that was about 457 cc, and Homo habilis' brain was 552 cc. With her larger brain, H. habilis became the first significant tool maker. In 1931, Louis Leakey started an intensive search in the Olduvai Gorge in Tanzania for early human fossils. He was attracted to the site because it is in the Great Rift Valley, and the gorge cuts up to 90 m into the Pleistocene lakebed sediments. It was a good choice. Initially, Louis worked in Olduvai with his team. In 1937 he married Mary Nicol. Mary was a gifted archeologist and became Louis's collaborator. Later one of their children, Richard Leakey, continued their work. Just after arriving in 1931, Louis found a group of hand axes close by their camp. This find was just the start. They soon unearth hominin fossil fragments and more tools. For year and years, the discoveries continued. In 1960, Louis and Mary's eldest son, Jonathan, excavated the lower jaw and the top of the head of a juvenile hominin. Later other bones were found with the skull. In the end, they had wrist and hand bones and an adult foot. The remains did not match other species. Three years later, they unearthed a cranium with both the upper and lower jaw and a fragmented skull with well-preserved teeth. The fossils were in the same strata as the stone tools suggesting they were the tool makers. The Leakeys had discovered Homo habilis. The archeology showed that H. habilis lived in the Olduvai Gorge 1.9 million years ago. As the work continued, the Leakeys also found smashed and cut fossil bones. It looked like H. habilis were using the pebble hand axes to break open bones for the marrow and using the sharp flakes to cut meat off the bone.

By 1964 Louis Leakey et al. believed they had the evidence to prove that H. habilis was the first true toolmaker. Since then, researchers have excavated many more hominin remains and stone tools. As a result, there are now new candidates for the title "the first true toolmaker." However, many of the finds are just a few skeleton fragments. The remains might be enough to suggest a new species. However, it is not easy to draw the line between species. What is clear is that H. habilis was not the only toolmaker or perhaps the first. Despite these difficulties, the path remains the same. Brains were getting bigger, and stone tools were becoming more refined and practical.

The next artifact in the timeline is an Acheulean hand ax. When people think of a stone-age tool, this is what they typically visualize.  It is the shape of a teardrop, with a round bottom and two sharp edges tapering to a tip. The Acheulean ax dates from about 1.6 million years ago. At this time, in the Olduvai Gorge, H. erectus and Acheulean axes had replaced H. habilis and Oldowan tools.  The transition is not surprising because the new ape's brain was about twice as large as H. habilis (1016 ccs vs. 552  ccs).

The new hand axes were a big step forward. If a teenager or university student announced to her parents that she was learning stone toolmaking and a few weeks later came home with an Oldowan chopper and a few sharp flakes. There is a good chance her parents would not have been impressed. However, if she had brought home an Acheulean ax, they would have been full of praise because most people recognize the skill required to make a hand ax.

Just looking at a hand ax, you can see that making it requires imagination, knowledge, and skill. Dietrich Stout et al. set out to study just how difficult it was. He found that the biggest problem the toolmaker faces is reducing the thickness. An ax found at Boxgrove, UK (now in the British Museum) was 137 mm long by 90 mm wide and only 30 mm thick. The stone you start with is much thicker. To reduce the thickness, you need to create long flakes: long enough to cross the center of the stone. Before you can split off a long sliver, you need to prepare the surface you will strike. The angle of the face determines the length of the flake. Once you have made a face with the correct angle, you can knap the surface to produce a thinning shard. Through each cycle of preparation and thinning, you need to work towards the ax shape. If the process goes well, you will end up with a rough version of the ax. Now you must focus on the finer work to create the finished product. Using a grindstone, you prepare the edge for more delicate controlled knapping. Dietrich Stout also wanted to know how long it would take to learn the skills needed to make an Acheulean ax. So he and his team invited 20 people to sign up for 100 hours of standardized ax-making training. After 90 hours of teaching and practice, most of the students were able to make an ax. However, the quality of their work did not match the Late Acheulean axes found in Boxgrove. Stout estimated that it would take the student anything from 121 to  441 hours of lessons and practice to get to the Boxgrove standard.

Next on the timeline is a stone knife made by a Neanderthal. Neanderthals first emerged about 400,000 years ago. They had a stockier build than modern humans and a more ape-like skull. However, the reputation we gave them for being stupid probably says more about us than them. Two facts challenge this reputation. Firstly, Neanderthals had larger brains than us (1512 cc to 1355 cc). Secondly, they were smart enough to make a wide range of sophisticated tools. The stone knife in the picture above is a  delicate tool. It shows that Neanderthals were more skilled than H. erectus. They also had the imagination to create a wide range of implements such as stone spear points, scrapers, pronged harpoons, engraving tools, and many more. Neanderthals were also inventive. They discovered how to set stone ax heads into wooden handles and stone tips into spear shafts. These innovations made both tools much more effective. A hunter could swing a wooden-handled ax with much more force than a hand ax.  Similarly, a stone-tipped spear was sharper and more deadly than a wooden-tipped spear.

By about 300,000 years ago, another toolmaking species had emerged. The archeological remains of the new species showed that it had a skeleton that was the same as modern humans. We, Homo sapiens, had arrived. Like Neanderthals, these first modern humans made a wide range of tools. Despite having a smaller brain and lighter frame, humans displaced Neanderthals and by 25,000 years ago, they were extinct in Europe. How humans drove Neanderthals to extinction is not clear. The archaeological evidence does not provide an answer. What is clear is that, by the end of the stone age, people were making beautifully crafted tools. The fourth tool in the timeline is a polished stone ax head. Looking at a polished ax, you may think it was made more for show than effect. However, scientists have tested how effective they were. It turns out that knapped stone tools are not as good as polished tools for working wood. The new axes made it easier for our ancestors to fell trees and clear land for agriculture.

Despite its utility, a polished stone ax is a thing of beauty. It is easy to believe that someone skilled enough to make such an artifact could have become a sculptor. In the same way that Michelangelo saw the angel in the stone, the Neolithic toolmaker saw the ax head and set it free. Both pictured in their minds what they wanted to make.

In 1924 Albert Einstein wrote, "Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution."

What do you think? Does progress start with imagination?