Using the DNA data, the researchers argue that humans and chimp lineages evolutionarily diverged from one another between five and six million years ago. Many other genera more distant to people, some squirrels for example, include groups of species that have diverged from one another far earliermany between 7 to 11 million years ago. Species groupings should be equivalent between different groups of animals, said Goodman. "An objective yardstick is the age of origin of a branch [of animals]," he said.
"Historically, the philosophy behind how we group organisms was flawed," said Goodman. Starting with Aristotle in ancient Greece, species have been grouped according to their "degree of perfection," with man as the pinnacle. This "anthropocentric," or human-centered, view led to "exaggeration of the differences between humans and their relatives," he said, noting that his study gives "an objective view of man's place in the kingdom of life."
Confusion and Opposition
"This is an attempt to pull the classification of humans in line with other species and is fundamentally a good idea if you want to accurately reflect the evolutionary differences between organisms," said Cristophe Soligo of the Human Origins research group at The Natural History Museum in London, England. Humans have been the "odd-one out" in terms of mammalian classification, he said.
"However, whenever there is a big change in [classification] practice, it also leads to a lot of confusion and opposition," said Soligo. "The closer you get to humans the more contentious the issues become."
Reclassifying chimps would also have "political implications," challenging our long-held view of the boundary between humans and other animals, he said. Many recent studies "are contributing to blurring the boundaries between our species", said Soligo.
"The argument is whether genetic relatedness is the only thing you should take into account," said anthropologist Bernard Wood at George Washington University in Washington, D.C. "A genus should also be a group of very similar species, that share attributes such as behavior and [mode of movement]," he said.
Fossil human-like species are currently divided into at least three genera. Grouping them all in the genus Homo could be very confusing, Wood said. Classification schemes "should be the signposts for differences between organisms," said Wood. "The problem is, if you call the chimp Homo troglodytes, you deny yourself that tool to help guide you through the tree of life."
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