Douglas Ubelaker of the Smithsonian National Museum of Natural History is an expert at identifying human skeletal remains. To make identification easier, the physical and forensic anthropologist determines the standards for skull size and shape in specific populations.

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With anthropologists from North Carolina State University and the University of South Florida, Ubelaker recently studied more than 200 skulls from 16th to 20th century Spain and about 50 skulls from 20th century Portugal. What the researchers have found, according to their study in the journal of Forensic Science International, is that the facial structure of men and women, at least in Spain, are more similar now than they were in the 16th century, when the craniofacial features of women were significantly smaller.

"The causes are of course difficult to discern. We know that cranial morphology is a product of both genetics and environmental factors, including diet," says Ubelaker. As his paper notes: "Past studies have shown that improvements in nutrition, living conditions and socioeconomic environment have led to positive secular changes, which could account for the changes observed between the Spanish samples."

The finding will be useful to anthropologists trying to identify the sex of skeletal remains based on skulls. In addition, the comparisons of skulls over several centuries helps piece together population histories and individual ancestries. "Migration adds complexity especially in areas of Europe that likely witnessed major movements of people in the past," says Ubelaker.

An earlier project had recorded patterns of cranial variation in skulls predating 1492 from Latin America. But Ubelaker and his colleagues wanted to add a European perspective, and so studied these documented skull collections in Spain and Portugal.