UNIVERSITY PARK, Pa., Jan 08, 2002 (Daily Collegian, U-WIRE via COMTEX) -- The importance of teeth extends past eating, as their remains have shown that the complete maturation of human beings seems to have occurred much later in human evolution, researchers said.

Alan Walker, Pennsylvania State University distinguished professor of anthropology and biology, assisted on the study, which was written by Christopher Dean of the University College, London. Walker was one of the first scientists to use scanning electron microscopes to examine fossilized teeth.

In the womb, markings or increments are found in teeth as they develop in the gums.

"Your teeth are made of cells called ameloblasts," Walker said. "These are little cells that start out when you are an embryo."

During the development, the ameloblasts move out and leave a protein called amelogenin. After the amelogenin is calcified it becomes enamel. This process provides important information for scientists. When a child is born, it is a shock to the body, and the teeth stop growing for a day, Walker said.

"There is a line of interrupted growth," he said. "That's the start of our counting."

The researchers start with the first molar and work to the third one because molars are permanent teeth. By counting the increments, the scientists were able to tell how long it took different animals to develop fully.

The researchers studied the remains of teeth from African apes, australopith hominins, which are part of the very beginning of the human lineage, and various creatures in the Homo genus.

Apes and other primate creatures reach adulthood at 11 or 12 years of age. The data gathered from the examination showed the development of the first humans was comparable to that of primates, such as the African apes.

The scientists re-examined a child's skeleton Walker discovered in 1984 in Kenya. The calculations to determine the age of the child were based on human growth patterns, and it was thought the child was a pre-adolescent because it was 5 feet, 3 inches tall.

Using the teeth as a road map, the researchers found the child was closer to eight years old. The results amazed Walker and his colleagues.

"A big surprise to us is that very early humans fall into the ape range," he said.

The skeleton was a Homo erectus, which is the first human fossil ancestor that demonstrates modern human physical characteristics. The scientists thought the growth period of Homo erectus would be closer to present-day humans.

"Our fossil ancestors developed very quickly," said Dean Snow, head of Penn State's anthropology department. "Youngsters were fully mature at eight years old and sexually active."

The closest link the scientists discovered to present-day human beings was found in a Neanderthal from Israel that was more than 120,000 years old.

"It was growing up slowly like a (modern) human," Walker said.

The growth of the brain is a very long process and separates early humans from current ones.

"If you live a short time, you don't have enough time to learn things and grow a big brain," Walker said.

More studies into this new discovery are on the horizon.

"We have to do more (research) like this," Walker said.

He wants to examine fossils more extensively between those in the early Homo genus and Neanderthals.

The findings were published in last month's journal Nature.