To Map Is Human

Scientists employ extraordinary imaging technologies, such as functional magnetic resonance imaging, combined with the most sophisticated kinds of analytical software, run on ever-more-powerful computers, to map just how thoughts, feelings, and other aspects of human cognition are produced and rendered in the human brain. Journals dedicated to this enterprise, such as NeuroImage and the aptly named Human Brain Mapping, are full of complex and colorful maps of the brain, which it is hoped, will someday collectively lead to a thorough understanding of brain structure and function. The human brain is often referred to as one of the "final frontiers" of science. This is a deliberate attention-grabber of a label, designed to appeal to the widespread human urge "to go where no one has gone before." A map is not just the desired product of exploring new frontiers and making them available to those who follow: it is also proof that the journey was made.

So we have reached the point in history where the human brain can map its working self, in living, breathing bodies. But when did the map-making urge begin? Certainly, there is quite literally hard evidence of map-making dating back to the Upper Paleolithic of Europe. In eastern Europe, an incised stone discovered at a well-investigated archaeological site (dating to 25-30,000 years ago) in the Moravia region of the Czech Republic, may represent the passage of a group of herding animals through a bottleneck in the mountains. A possibly less ambiguous example of a map has recently been discovered by a group of Spanish researchers, led by Pilar Utrilla of the University of Zaragoza (Journal of Human Evolution 2009, 57:99-111), which suggests that maps may have been made and used in western Europe (south of the Pyrenees mountains in northern Spain) about 14,000 years ago. In this case, the map is an incised block of stone weighing about a kilogram. The block clearly contains carvings of animals; in addition, there are numerous lines and shapes on its surface, creating what Utrilla and colleagues refer to as a "landscape layer" mixed in with the "animal layer." The lines may represent hunting routes; in addition, some of the carvings appear to illustrate geographical features of the valley surrounding the cave site where the map was found.

This hard early evidence of mapping is, of course, not very hard at all in terms of certainty or conclusiveness. The lines and scratches on these rocks are just that--lines and scratches irretrievably divorced from their original symbolic and cultural contexts. The best evidence for the evolution of human mapping may come not from the relatively recent (in evolutionary terms) evidence of drawn maps, but from a greater understanding of the cognitive basis of spatial orientation and how different cultures have elaborated upon the cognitive baseline to develop sophisticated ways of navigating through the environment. Over the years, anthropologists have studied the ways in which "extreme" navigators such as Micronesian sailors, south African San Bushmen hunters, and other groups make their way over great distances in featureless (to outside observers) environments. Do the methods employed by these extraordinary navigators help us understanding human mapping in general?

In a recent review, Kirill Istomin and Mark Dwyer (Current Anthropology 2009, 50:29-49) discuss the two anthropological models based on ethnographic research that have been proposed to account for the "wayfinding" ability of humans. One way humans routinely navigate is through the creation of "mental maps...abstract cognitive representations of the spatial relations between objects." Conventional maps, printed or carved or whatever, are manifestations of these mental maps made available to other observers. As Istomin and Dwyer point out, mental maps are actually quite powerful cognitive tools, because beyond simply representing known routes, they provide a means by which totally novel routes and spatial relationships between objects can be established, without actually physically traveling the routes. In contrast, the "practical mastery" model of human wayfinding posits that the only way that humans navigate is through the memorization of routes based on the movement from one visual perspective to another. Such landmark-based navigation can be very effective but does not match the creative power that generalizing from mental maps provides.

Istomin and Dwyer argue that although some anthropologists have been quite supportive of the practical mastery model, studies from experimental psychology and other disciplines indicate that human wayfinding depends primarily on mental maps. However, these mental maps can be influenced by a wide variety of cultural and demographic factors, which makes practical mastery an integral component of mental map-making. Istomin and Dwyer's own ethnographic research on two northern Eurasian reindeer herding groups, the Komi and Nenets, demonstrates the ways in which mental maps vary according to specific cultural practices. The Komi and Nenets manage their reindeer herds in very different ways, with the Komi moving their herds among dispersed pasturelands linked by long migration routes, while the Nenets move their herds around within circumscribed regions they control. According to Istomin and Dwyer, these divergent practices lead to highly divergent mental maps of the same type of landscape the two groups more or less share.

From the perspective of an individual human actor, a mental map invokes an "allocentric" frame of reference, since it does not depend on locating the individual within the space being defined. A practical mastery model is fully "egocentric," given that all of its landmarks are based on the individual's self-perceived position in a sequence of localities. Tino Zaehle and colleagues (Brain Research 2007, 1137:92-103) have used functional magnetic resonance imaging to map the parts of the brain that are active during tasks of allocentric and egocentric navigation. The tasks were all auditory, to remove the possibly confounding effects of visual processing; for example, subjects were described a simple scene, and then asked questions about the spatial relationship among objects or with reference to themselves. Zaehle and colleagues found that the brain's processing of spatial information is generally hierarchical, involving a number of different brain areas (including visual areas despite the fact the subjects were not given visual stimuli), with egocentric processing largely constituting a subsystem of allocentric processing. Without worrying about the brain regions involved, it is reassuring to find that the two basic models of wayfinding derived from observations of real people moving around in the real world appear to have a valid cognitive basis, and vice versa.

From some scratches carved into a rock, indicating the location of game in a small valley 14,000 years ago to highly-processed images of a thinking brain on a computer screen, the human propensity for map-making has a long history. But in the same way that spoken language existed long before we had written languages, it is likely that mental maps, shared among our ancestors via language, have been around for much longer than the physical evidence of map-making would indicate. Maps are used for many things, but first and foremost among them is to plan ahead. This ability for "mental time travel," as Thomas Suddendorf and Michael Corballis (Behavioral and Brain Sciences 2007, 30:299-351) call it--to have the foresight to plan future actions--may have been an essential adaptation during the course of human brain evolution. When we map, we plan, and the ability to form mental maps and to share their contents with members of a social group may have provided our ancestors with a tremendous cognitive advantage.