Rethinking Our Genus

Early Fossils Were More Alike than Previously Thought

by Jenzl Guerrero, age 17

About 1.8 million years ago, there was a turning point in the evolutionary history of humans.

Fossils of our ancient ancestors older than 1.8 million years resemble chimpanzees and show few similarities to modern humans. Recent studies of younger fossils, however, show that our ancestors from 1.5 to 1.8 million years ago had a different structure. These fossils are flatter in the face, have larger brains, and are better suited for walking.

Unlike earlier observed fossils, which were found only in Africa, these new fossils were found in Asia, from the Republic of Georgia to Indonesia. Paleoanthropologists believe these fossils are the earliest members of our genus, Homo.

In 1891, paleoanthropologist Eugene DuBois spotted the first early Homo fossils. They formed an upright posture when reconstructed and are known as the species Homo erectus, which is different from the human species, Homo sapiens.

Following DuBois’ discovery, scientists continued to find a variety of fossils in other locations; these fossils were often categorized as different species than those previously found. Scientists thus created various names for species of the Homo genus. But the categorizations were based on a very moderate number of fossils. Years later, after much study, experts believe many of these early fossils could belong to just one species.

In the journal Science, a team of scientists reported comparing five skulls, each 1.8 million years old, from a site called Dmanisi in the Republic of Georgia. Though similar in structure to humans and chimpanzees, these skulls also exhibited an unprecedented range of physical diversity.

Continuing this research, G. Philip Rightmire, a Harvard University professor and co-author of the study, conducted a comparison between the Dmanisi skulls and skulls found in the Old World. These skulls proved to be diverse.

“They don’t represent distinct species,” said Dr. Rightmire. “They’re just one group.”

Although much evidence has been collected, some scientists remain uncertain if our ancestors come from one species or if they evolved from a variety of species.

“What we need, practically, is labels for them,” said Todd R. Disotell, a biological anthropologist at New York University. “We will never solve the species problem for fossils if we can’t for living, breathing animals.”

[Source: The New York Times]