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160,000-Year-Old Child Suggests Modern Humans Got Early Start

Kelly Hearn
for National Geographic News
March 14, 2007
 
Bucking conventional wisdom, a new study says early members of our species, Homo sapiens, may have known what it was like to be a kid.

A long childhood is considered one of things that separate so-called modern humans from the first Homo sapiens and older human species, such as Homo erectus.

Now a study of a 160,000-year-old early Homo sapiens child found in North Africa may change how early—and where—we think modern humans arose.

A Study With Teeth

European researchers used x-ray imaging to study the growth patterns of teeth in the juvenile fossil found in Morocco. Similar to tree rings, the patterns are a record of aging.

What they revealed is that this fossil is the earliest known human with a long childhood, according to Tanya Smith, an anthropologist at the Max Planck Institute for Evolutionary Anthropology in Germany.

In the teeth the scientists found signs of modern-human development patterns—that is, relatively long periods of slow development and growth. A prolonged childhood is seen as necessary for the type of learning that leads to culture and complex society.

The juvenile fossil "showed an equivalent degree of tooth development to living [modern] human children at the same age," the report authors write.

According to the researchers, the study challenges theories about when and where humans acquired modern bodies and behaviors.

The findings also may help prove that "modern biological, behavioral, and cultural characteristics" were relative latecomers in the past six million years of human evolution.

(Related: "Adolescence Came Late in Human Evolution, Study Shows" [December 5, 2001].)

"These findings are in contrast to studies that suggest that earlier fossil hominins [humans and our ancestral species] possessed short growth periods, which were more similar to chimpanzees than to living humans," the study authors write in this week's issue of the journal Proceedings of the National Academy of Sciences.

Study co-author Smith said her research team knew that human ancestors living several million years ago grew up differently from modern children.

"What we didn't know was when the modern human condition of a long childhood and slow period of growth and development evolved," she said.

The study suggests that developmentally modern humans existed at least 160,000 years ago, which Smith says is just slightly younger than the earliest fossil Homo sapiens from East Africa.

Promising New Method

"It is a great result that today we can really measure growth rates of teeth due to CT [and] x-ray technology," said Professor Ottmar Kullmer, a paleoanthropologist at the Research Institute Senckenberg in Germany.

"These new possibilities of modern analysis methods augment the understanding of early Homo sapiens development and human evolution in general."

Kullmer, who was not a participant in the study, said that the discovery of a relatively long human childhood about 160,000 years ago points to "a complex social system in early Homo sapiens groups."

"Probably, social behavior was one of the important survival strategies of early humans."

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