SCIENCE

A 1.8 million-year-old skull has rekindled debate over the identity of humanity’s ancient ancestors. (National Geographic News)

Use our resources to better understand hominins and the human family tree.

Discussion Ideas

• Read our terrific GeoStory “Hominin History,” which briefly outlines different hominin species, from S. tchadensis to H. sapiens sapiens. The authors of the new study profiled in the Nat Geo News article suggest that many of these species may be misidentified—that is, they may all actually be one species. (Read the study itself here.) Which of the species in “Hominin History” might be misidentified?
  • All the “early Homos” : Homo habilis, Homo erectus, and Homo heidelbergensis, to name a few.

• Review the “Hominin History” GeoStory. What characteristics do “early Homos” share? What characteristics make them distinct from each other? (Use this image, from the original Dmanisi discovery, for some hints.)
  • Shared Characteristics: All early Homo species had larger brain cases than their australopithicine cousins (an important characteristic for the Dmanisi study), although brain size varied widely within the Homo group. All early Homos also used primitive tools, earning H. habilis the nickname “handy man.”
  • Distinct Characteristics: H. erectus was distinct from other hominins in many ways: It had longer arms, shorter legs, and a larger brain case (all similar to modern humans.) H. heidelbergensis developed more complex tools than other early humans, building shelters, hunting large species, and possibly controlling fire. H. habilis fossils have not been discovered outside Africa, possibly indicating that this species did not migrate out of the continent as other early human ancestors did.

• One set of scientists (supporters of the Dmanisi study) thinks that all “early Homo” fossils may be a single, diverse species—probably the remarkable H. erectus. (Read the New York Times article for a great presentation of this theory.) Another set of scientists doubts this radical theory, saying that the new data only considered the shape of a fossil’s skull, not the rest of its anatomy. (The Nat Geo News article is the best source for this critical view.) Consider species studied in “Hominin History.” Which scientists present a more convincing argument to you? Why?