In its decade-end round up, the Globe and Mail reported that in 2008, for the first time in human history, more people lived in cities than in rural areas. Surely, urbanization can be studied through many perspectives, but researchers from University College London’s AHRC Centre for the Evolution of Cultural Diversity have approached the importance of population density from a unique angle—one that combines archaeology, demography, and behavioural studies.
According to researchers Adam Powell, Stephen Shennan, and Mark G. Thomas, as far back as the Pleistocene era (ending about 10,000 years ago), ideas have been most easily transmitted and shared in small geographic areas inhabited by large numbers of people. The UCL group’s report, published in the journal Science, argues that population density can be understood as one of the crucial factors that helps facilitate human progress and development over time.
How can researchers determine how ideas got around tens of thousands of years ago? It helps to start with the brain. One of the features distinguishing Homo sapiens from the earlier Homo erectus is increased cranial capacity, and to an extent, a bigger brain was the catalyst that allowed Homo sapiens to acquire modern human behaviour. Archaeologists can infer early examples of skill-building when they discover artifacts such as musical instruments, artistic works, and food-gathering technologies as part of human remains.
So, what’s the issue? Although Homo sapiens emerged about 200,000 years ago, the archaeological record suggests that humans have only used the skills associated with these technologies in the last 90,000 years. Clearly, modern human behaviour came much later than the possession of a big brain.
To examine why new capabilities emerged some 110,000 years after increased cranial size, the researchers worked with demography as a frame of reference. They made use of a computer program to simulate the rate at which advanced skills were adopted by populations of varying densities. The team also simulated subpopulation migration to examine the point at which diversifying groups developed modern human behaviour.
Thomas shared a critical result in a telephone interview with Live Science’s Jeanna Bryner. “As population density increases,” he explained, “people migrate between groups more. That increases the probability that any skill that’s difficult to learn doesn’t get lost or decay.” The archaeological evidence also syncs with this conclusion: similar behaviour-revealing artifacts have been uncovered in parts of Africa, Europe, and the Middle East at points in time when these regions had similar population densities.
Finally, Powell, Shennan, and Thomas’ findings help to explain a strange phenomenon within the archaeological record of sub-Saharan Africa. Remnants of art and complex technology have been found in the region dating to 90,000 to 65,000 years ago, but evidence then becomes scant until about 40,000 years ago. Is it possible that modern human behaviour could disappear from an area for 25,000 years, only to re-emerge at a later time?
Sure, if you’re considering the issue of population density. During these 25,000 years, sub-Saharan Africa was experiencing climate change that resulted in human groups being fewer and farther between. It just goes to show that increased intellectual capacity from having a bigger brain, as Homo sapiens did during this period, doesn’t automatically result in advanced skills—it matters just as much with whom and how close together people are living.
Beyond providing a solution for one particular archaeological quandary, this report is already being cited in research across a variety of disciplines from environmental psychology to economics to cognitive science. It also lines up nicely with contemporary urban theories that stress the benefits of city living to promote the exchange of ideas and to solve problems.
On the whole, however, research linking demography to development serves to clarify that age-old maxim of social networking: it’s not what you know, but rather who you know that matters. So if you’re looking for an extra reason to go to a party this weekend where you won’t know many people, consider this study your new incentive. Co-mingling with foreign people in tight spaces certainly proved advantageous in the long run for those Pleistocene-era Homo sapiens.
