The Evolution of Intelligence

Renato M.E. Sabbatini, PhD
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Alongside with language, the ability of inventing and making new tools is considered one of the most distinctive features of Homo. No other living animals have these abilities, and probably the extinct hominids had them in a primitive, initial stage, setting the difference with other non-human primates. Therefore, the emergence of a technology to manufacture stone tools during the evolution of hominids represents a radical social and behavioral departure from apes, and is the first documented evidence for a cultural tradition with value for survival, i.e., based upon learning.

Humans first made tools 3 to 4 million years ago. They were probably made of wood or bone, since chimpanzees are able to "fashion" twigs of wood for several purposes, but there is no way of knowing this for sure, because no fossil remains of these were found. Stone tools, however, were perfectly preserved and are very easy to distinguish from natural forms. There is no firm evidence that the Australopithecines were able to manufacture tools, but almost certainly they used natural objects for this purpose. The appearance of Homo habilis, however, made the difference. Humans first made tools of stone 2.5 million years ago in Africa, starting what is known as the Stone Age, and which progressed over time through three distinctive eras:

• the Paleolithic, thus named from the Greek words "paleo" (old) and "lithos" (stone);
• the Mesolithic ("middle" and "stone");
• the Neolithic ("new" and "stone").

Flint tools of the Acheulean (Paleolithic) period

Stone tools of the Olduwan (Paleolithic) period

Humans used them to kill animals, break bones, slice meat, scrape hides, cut branches and sharpen wood sticks. Access to rich sources of fat and protein hidden in bone marrow, brain and muscles of dead or fresh-killed animals was very important for men's further evolution, because it provided them with enough energy to sustain a larger brain, as well to run for a long time after edible prey. Hominids and early humans lived probably on a mixed diet obtained by foraging, scavenging and hunting. These three activities are progressively more effective in terms of caloric return of investment of time and effort, and the "discovery" of tools for scavenging for the brain and bone marrow and for killing prey was the major amplifying factor that "exploded" human evolution within a few hundred thousand years.

Later on (1.5 million years ago), a technique known as Acheulean was developed in Africa and reigned for one million years without modification. It was carried by Homo habilis and Homo erectus to Asia and Europe. Acheulean tools were more refined, larger and simmetrical, formed in the shape of teardrops, with edges around the entire stone, while Olduwan tools were rougher, smaller and irregularly shaped. Acheulean toolmakers had the capacity to superimpose a pre-conceived form upon an unfinished stone, which requires a more sophisticated form of intelligence.

The earlier Homo sapiens, such as Neanderthals, evolved flaked stone tool technology, too (Middle and Upper Paleolithic), but they were far less sophisticated and less varied than those of early modern humans.  The most advanced and innovative form of stone toolmaking appeared in the Neolithic, about 40,000 years ago, and is totally characteristic of the superior abilities and intelligence of Homo sapiens sapiens. .It demanded great skill and knowledge and resulted in longer and thinner blades which had 10 times more cutting edge than those of  Middle Paleolithic. In fact, it is still in use today by many cultures throughout the world, such as South American Indians. It used a precision technique of indirect hammering, developed by Cro-Magnon humans, which lead to 60 to 70 different tools for all sorts of tasks, ranging from sewing and cutting to boring, scraping, sawing, hammering, excavating, etc. Astonishingly large "flint tool plants" were found in France and other parts of Europe, with hundreds of thousands of tools in several stages of completion, production lines, tons of debris and residues of toolmaking, and raw materials brought from distant places. There was also the first evidence of commerce of stone tools among tribes, probably by bartering.

The art of hunting and warmaking was also considerably advanced by all sorts of weapons, such as slingshots, bows, piercing and blunting arrows, axes, spears, knives, etc. In this way, man's intelligence, planning and cunning capabilities co-evolved with his capacity to kill enemies and competing tribes, conquest territory and access to water and food, hunt down cooperatively large prey, defend against predators, build houses and boats, protect against cold and wheather, migrate to other lands, and many other things.
 

Hunting is the foremost human activity and it was made possible only by the invention of hunting weapons. Hunting exists and is instinctive among chimpanzees, which hunt for small prey, such as baby monkeys and antelopes, in bands as large as 10 individuals. They kill by flailing, thrashing and beating. However, using tools for rapidly and effectively killing large preys and in a large number, is uniquely human. There is evidence that Neolithic humans were able to kill mastodons, the largest land mammal that ever lived. This was a huge and very dangerous feat in itself, as it is shown in this exhibit in the Anthropological Museum of Mexico, and required incredible skills of planning, execution, group coordination, technology, etc.

Homo erectus was probably the first human species to hunt cooperatively using weapons. In some archeological sites, a large number of bones of animals, stone weapons and tools were found alongside remains of Homo erectus. In some sites there were the remains of more than 50 elephants, a very large prey. Another key fact is that they were the first to discover the use of fire, which made it possible for them to inhabit regions with very cold weather, such as northern China, and to preserve meat to take along long trips across deserts and mountains.

Why was hunting so important? Why is it also a distinctive characteristic of the human primates? According to Craig B. Stanford, in his bool "The Hunting Apes", "the origins of human intelligence are linked to the acquisition of meat, especially through the cognitive capacities necessary for the strategic sharing of meat with fellow group members." Chimpanzee males exchange meat for sexual favors from females, for instance, and there is a selective advantage in sexual selection because of this. Probably humans made extensive use of meat not only as food, but also to influence social structure, reproductive success, etc.

Weapons for hunting were quickly adopted by humans to kill his own species. The impressive "The Dawn of Man" opening sequence of 1968 Stanley Kubrick's movie picture "2001: A Space Odissey" shows how hominids could have come to discovery of the usefulness of tools to assure dominance and self-defense. Warring as a way of dominating and anhilating other human groups is also very ancient. According to several theories, "sub-speciation", i.e., the dominance of a group of animals over other groups of the same species by competition, was very important for the rapid evolution of modern humans. The Harvard zoologist Dr. Edward O. Wilson, of  "Sociobiology" fame, has argued that systematic genocide, as it is practiced even today, was a form found by the human species to accelerate the work of Nature and to promote the gene pool of a particular group. The incidence of war in human history is more than enough to document this permanent feature of human intelligence and culture. Killing other humans for food was also important. Cannibalism among Neanderthals, for example, was demonstrated by recently discovered remains of human bones bearing cutting and scraping marks of bone tools, very similar to those found in animal preys.

In conclusion, we can say that without stone tools, humans would not have evolved a superior intelligence, and vice-versa. These abilities evolved from bipedalism, which freed the hands for these tasks of handling, carrying and manufacturing, as well as the development of a special kind of thumb, found only in human primates. Since toolmaking is not an innate or instinctive ability and cannot propagate via genes, the only way to pass it from generation to generation is by means of cultural tradition, imitation learning, training, etc., which also presuposes some effective form of communication between master and apprentice: this can be seen as the origins of practical education and of language! Monkeys can learn by this way, too (as it was proved by the now famous study of Japanese macaque monkeys, which spread a "culture" of washing potatoes given to them by researchers), but the absence of language severy limits the scope and depth of cultural learning.

"The Evolution of Intelligence" Renato M.E. Sabbatini, PhD Brain & Mind Magazine, February/April 2001

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