A study of various ethnic groups suggests that the average height of an individual may provide clues to where his distant ancestors lived, and what was their lifestyle.
The study basically links the evolution of human body size to past population density and location.
Its findings show that height can vary hugely even among individual family members. Nevertheless, each society illustrates a distinctive body size, with some groups being shorter or taller on average than others.
"Of course there is considerable variation within societies that relates to many different nutritional, genetic and perhaps even selection pressures," Discovery News quoted co-author Robert Walker, a postdoctoral researcher at the Max Planck Institute for Evolutionary Anthropology, as saying.
"But despite this variation (within societies), the mean body size varies widely -- by a factor of two -- across societies. So your average Agta (an indigenous Philippine group) is much smaller than your average Inuit (an indigenous Arctic dwelling group)," he added.
During the study, Walker and his colleague Marcus Hamilton focused on existing hunter-gatherer groupslike Pygmies, Philippine Negritos and Andaman Islandersthat tend to fall into the shorter end of the height spectrum.
The researchers gathered data on the ecology, population density and female adult body size in 32 such groups.
"We focused on female adult body mass because we wanted to relate the variation back to female reproduction," Walker said, adding that earlier first periods relate to earlier first births.
The analysis of the data determined that body size directly relates to population density across all hunter-gatherer groups. The bigger the population, especially within island or island-like communities, the smaller the people will be.
Given that previous studies attributed shorter heights to lack of nutrition, the researchers theorise that greater competition for resources and a higher instance of disease spread exist in densely populated areas.
Since mortality is consequently higher, natural selection favours earlier maturation so that individuals can reproduce before their death.
"For any given growth rate, if you stop growing earlier and start reproducing earlier, you are a smaller adult. This may be going on in some human groups where mortality is high," Walker said.
Walker and Hamilton believe that studying the effects of ancestral population density and ecology on height may help resolve longstanding anthropological mysteries.