In 1965, Harvard paleontologist Bryan Patterson discovered a hominin fossil elbow (specifically, a distal humerus fragment) in the Kanapoi region of Kenya, just west of the southern end of Lake Turkana. Very little follow-up work was done until twenty-five years later, when Maeve Leakey organized digs in the area once again and uncovered fossils that would be classified (along with the elbow) as Australopithecus anamensis. Her team described the new species based on the new fossils found at Kanapoi and additional fossils found at Allia Bay, another site farther north on the eastern shore of Lake Turkana. The fossils were different from the other australopith species known from that region, the famous Lucy species A. afarensis. The fossils were conventionally dated to about 4 million years old.
Despite having enough fossils to recognize the new species A. anamensis, there were only upper and lower jaws from the head. Since most phylogenetic (and baraminological) analyses use characters from the whole head, I haven’t been able to say much about A. anamensis. What little information we could gather from the teeth and jaws allowed researchers to place A. anamensis deep in the hominin phylogeny, branching from a point earlier than A. afarensis. I’m a bit pickier with baraminology, and I haven’t made a systematic effort to understand what A. anamensis actually is.
And that’s about to change.
Today, researchers from the Cleveland Museum of Natural History and the Max Planck Institute for Evolutionary Anthropology announced the discovery of an A. anamensis cranium from Woranso Mille, a site about 700 miles north of Kanapoi in the Afar region of Ethiopia. The fossil was discovered in 2016, and it came from an aged individual that was probably male.
The cranium, known as MRD, is noticeably different from known A. afarensis skulls. MRD is smaller with a much more projecting face. Down the center of the skull runs a sagittal crest for attachment of jaw muscles. The skull is longer and narrower than A. afarensis skulls. To my eye, MRD looks more like a living ape like a gorilla than A. afarensis does.
Just a few days ago, someone asked me what I could say about the created kinds of apes. I had to tell them that I didn’t have much to say at all. We have a lot of fossils demonstrating the diversity of humans in the past, but ape fossils aren’t as well represented. Lucy is a well-known example of A. afarensis, and that species has consistently shown itself to cluster away from humans in my analyses. The South African species A. africanus also tends to be distinct from the human cluster, but it doesn’t really show much similarity to A. afarensis. The three robust australopith species, now generally placed in the genus Paranthropus, cluster together but separately from A. africanus and A. afarensis. Other than that, I don’t have much to say. As I continue to wait for new research on the A. africanus Little Foot skeleton, this new skull will provide yet another sample of this curious ape group.
What makes these creatures so surprising is the unmistakable attributes for upright, bipedal walking. The many Paranthropus fossils possess attributes of upright walkers. The knee of A. anamensis is known from Kanapoi, and it exhibits the anatomy of a creature that walks on two legs. Three skeletons of A. afarensis (Lucy, Kadanuumuu, and Selam) all show numerous traits possessed by creatures that habitually walk on two legs. Perhaps most spectacularly of all, the Little Foot skeleton from the Sterkfontein cave in South Africa preserves a nearly complete skeleton of one individual that clearly walked on two legs.
The existence of bipedal animals that look so similar to us raises many questions about God’s design and their relationships to each other. How many created kinds of upright apes are there? In past analyses, Paranthropus seems well-separated from other australopiths, and A. afarensis and A. africanus are also very distinct. Are these patterns merely the result of a sparse sample of species? Will we eventually find that all bipedal apes belong to one created kind, distinct from humans? What can this new skull tell us about even less well-known fossils like Ardipithecus or Sahelanthropus?
Congratulations are certainly in order to Yohannes Haile-Selassie and Stephanie Melillo, the lead researchers on the A. anamensis skull MRD. I certainly look forward to examining their findings in more detail. And I can’t wait to see what surprising fossils God has for us next!
References
Haile-Selassie et al. 2019. A 3.8-million-year-old hominin cranium from Woranso-Mille, Ethiopia. Nature DOI 10.1038/s41586-019-1513-8.
Leakey et al. 1995. New four-million-year-old hominid species from Kanapoi and Allia Bay, Kenya. Nature 376:565–571.
Ward et al. 1999. The New Hominid Species Australopithecus anamensis. Evolutionary Anthropology 7(6):197-205.
Photo: Dale Omori, Cleveland Museum of Natural History.
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