Our Early Ancestors: Were There Fewer Hominid Species Than Previously Thought?

Around 1.9 million years ago, it’s thought that the first members of our Homo genus appeared on the evolutionary scene. Probably the most well-known member is Homo erectus, who likely originated in Africa and, from there, migrated out to Europe and Asia (though some experts argue that an older migration occurred). The successful, just over five-foot-tall H. erectus made beautifully carved hand axes, used fire, and cared for their sick and elderly.

Living around the same time as early H. erectus (from about 1.3 to 1.9 million years ago), researchers have thought that other Homo species were also in Africa, including Homo rudolfensis, Homo habilis, and Homo ergaster. But, according to a paper published in the magazine Science last month, a recently-discovered 1.8-million-year-old skull may change this theory – instead of there being many different Homo species, these seemingly different species may all just belong to a single, diverse Homo species.

The skull, found in Dmanisi, in the Republic of Georgia, has a combination of features that have not been found in a single individual before – a large face, jaw, and teeth, but a very small brain. As an anthropologist at the University of Zurich, Christoph Zollikofer, explains, “Had the braincase and the face of the Dmanisi sample been found as separate fossils, they very probably would have been attributed to two different species.” This skull was found together with several other hominid’s skulls and bones, allowing researchers to compare the range of physical traits that individuals of that time and location had.

The finding of this skull has significant implications for the field, and our evolutionary history – there may have been fewer hominid species than previously thought, and instead just greater variation within a single Homo species. But this shouldn’t be too surprising – the proposed variation is no greater than the variation seen within the Homo sapiens population as a whole today.

This is just one more discovery showing that our ancient ancestors were likely around others beings who were not so different from them. (For example, more evidence recently revealed that Neanderthals, who we share up to 4% of our DNA with, were more similar to our Homo sapiens ancestors than previously thought.)

For further reading:

• Teisha J. Rowland’s book Biology Bytes: Digestible Essays on Animals Both Commonplace and Bizarre
• David Lordkipanidze et al.’s article “A Complete Skull from Dmanisi, Georgia, and the Evolutionary Biology of Early Homo” in Science
• ScienceDaily’s article “Unique Skull Find Rebuts Theories on Species Diversity in Early Humans”
• Teisha Rowland’s article “Neanderthals: Not That Different After All”