Fossil Apes: Homo Habilis and Homo Rudolfensis

From the August 07, 2012 eNews issue
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The famous fossil hunting family, the Leakeys, on August 8th announced the excavation of a face and two jaw bones tentatively belonging to the ancient hominin Homo rudolfensis, with zoologist Dr. Meave Leakey declaring, "At last we have some answers." The mother-daughter team Meave and Louise Leakey, wife and daughter of Richard Leakey, discovered three new fossils between 2007 and 2009, which they hope will shed light on ancient hominin evolution. 

Scientists have long struggled to put together an accurate human family tree, one that provides a tidy portrayal of the descent of Homo sapiens from the ancestors of humans and today's apes. Paleoanthropologists have been frustrated to find, however, that the tree of human evolution looks less like a straight and true cedar and more like a wild and untrimmed bush – or set of bushes. This most recent set of finds supposedly clears up questions about one branch, but when putting together broken bits of ancient skulls, things can easily get tangled.

In 1972, a member of the Richard and Meave Leakey team found a new skull at Koobi Fora on the east side of what was then called Lake Rudolf (now Lake Turkana) in Kenya. The cranium possessed a sufficient number of unique characteristics to be considered an oddity. It had a large, flat face and a larger braincase. It was called KNM-ER 1470 and was nudged timidly into the genus Homo as a new species, Homo rudolfensis. The skull had no teeth, no mandible – no lower jaw – and it created a whir of debate over whether it shouldn't be placed within the umbrella of the earlier established taxonomic group Homo habilis.

The newest skull and jaws produced by the Leakeys, discovered within about six miles of the 1470 site in the same region of Kenya, have also been suggested as belonging to Homo rudolfensis, offering evidence that this strange creature was not merely an aberration. KNM-ER 62000 looks a bit like 1470, though smaller in size. The face and partial jaw have been dated to 1.9-1.95 million years in age. The more complete lower jaw has been dated to 1.83 million years ago – all of which match closely in age to the supposedly 1.9 million-year-old 1470 specimen.

Adam or Ape?
The big question between the paleoanthropologists right now is whether 1470, 62000, and the associated jaws should be properly called H. habilis or H. rudolfensis or some new hominin species. The finds have generated some excitement that 1470 might have its own family after all.

In the end, though, it is clear that the discovery has very little to do with human history. Neither Homo habilis nor Homo rudolfensis are considered direct ancestors of modern humans. All concerned agree that the one demonstrated human relation in the area, Homo erectus, existed at the same time as H. habilis and H. rudolfensis. As Dr. Leakey and her colleagues wrote in the August 9, 2012 issue of Nature, "The new fossils confirm the presence of two contemporary species of early Homo, in addition to Homo erectus, in the early Pleistocene of eastern Africa."

Ian Tattersall of the American Museum of Natural History in New York City, commented on the Leakeys' new study, saying, "This new material certainly substantiates the idea, long gathering ground, that multiple lineages of early Homo are present in the record at Koobi Fora."

Theirs is a multi-branched lineage, if "lineage" is the right word at all.

More important than the kinship between H. habilis and H. rudolfensis is the question of whether these fossils are related to us. Should H. habilis even be considered a human cousin? While it has been shoehorned into the Homo genus, a number of studies have placed H. habilis in a completely separate category from H. erectus and other humans. 

In 1994, Holly Smith of the Museum of Anthropology at the University of Michigan published a study on the teeth of ancient apes and humans and concluded that H. habilis fit better with the apes. After doing extensive analyses of Australopithecus, H. habilis, H. erectus and H. neanderthalensis teeth, Smith stated, "…Restricting analysis of fossils to specimens satisfying these criteria, patterns of dental development of gracile australopithecines and Homo habilis remain classified with African apes. Those of Homo erectus and Neanderthals are classified with humans…"

Dr. Bernard Wood, a former surgeon and a notable expert in ancient hominid specimens, has long distinguished between H. erectus and the ancient apes. In 2007, Wood and paleoanthropologist Dr. Mark Collard updated their 1999 argument that H. habilis and H. rudolfensis should be placed in the same genus as Lucy, the Australopithecine, saying: "We find that, on balance, the available evidence still supports their suggestion that Homo should be reconfigured such that it includes H. ergaster, H. erectus, H. heidelbergensis, H. neanderthalensis, and H. sapiens but excludes H. habilis and H. rudolfensis…"

Why? According to Wood and Collard, the body size, body shape, locomotion, jaws and teeth, development, and brain size of H. habilis were all like the australopithecines, while the other Homo species were like humans.

Of Daschunds and Great Danes:
The early humans demonstrated variation, but were all similar enough to be considered closely related. Despite size and bone thickness differences, there has been question about whether H. ergaster and H. erectus were separate species, whether H. erectus were not simply a smaller version of H. neanderthalensis, and whether the Neanderthals themselves should even be classified as a separate species from Homo sapiens, based on DNA studies.

H. habilis and H. rudolfensis, on the other hand, are just plain outsiders.

Wood and others, like UC Berkeley evolutionary biologist Tim White and Milford Wolpoff at the University of Michigan, recognize that there can be a wide range of morphologies between members of the same species, and they are not quick to say that H. habilis and H. rudolfensis are that distinct from one another. If we were to compare the skulls of a Pekinese and a terrier and a great dane, it would be easy to assume separate species based on superficial differences.

Associated Press writer Seth Borenstein paraphrased White, saying, "[I]t's similar to someone looking at the jaw of a female gymnast in the Olympics, the jaw of a male shot putter, ignoring the faces in the crowd and deciding the shot-putter and gymnast have to be a different species."

The number of complete specimens are few in number, and it's easy to jump to premature conclusions base on too little evidence. 

"So where do we go from here?" Dr. Wood asked in his commentary. "More work needs to be done using the faces and lower jaws of modern humans and great apes to check how different the shapes and the palate can be among individuals in living species."

True Humans:
Ancient humans like the Neanderthals and their smaller cousin H. erectus may have (mostly) died out, but they were just as human as any of us.

Yet, while these scientists look at these issues through evolutionary eyes, their views correspond to the Biblical position that all human beings are ultimately related. If all of humanity but Noah and his family were wiped out, we should expect to see a variety of human groups in the fossil record, but only a relatively thin strain surviving to the present day.

The three fossil specimens announced on Wednesday may provide the world with new questions and maybe some new answers. The most notable fact, however, is that these specimens were found in the same layer as Homo erectus fossils, ancient apes and ancient humans living at the same time.

Related References:
• Early Man Was Not Alone, Study Finds - The Sydney Morning Herald
• New Fossils Indicate Early Branching of Human Family Tree - The New York Times
• Leakeys Say Fossils Confirm Theory Of More Pre-Human Species; Others Say Findings Flawed - AP
• Patterns of Dental Development in Homo, Australopithecus, Pan, and Gorilla. - The American Journal of Physical Anthropology (July,
1994)
• New Fossils From Koobi Fora In Northern Kenya Confirm Taxonomic Diversity In Early Homo - Nature (August, 2012)
• Defining The Genus Homo - Mark Collard, Bernard Wood
• Homo Habilis - Darwinism Refuted
• Human Origins, Apes Or Adam? - Koinonia House eNews May 10, 2011
• Hominid Mandibular Corpus Shape Variation And Its Utility For Recognizing Species Diversity Within Fossil Homo - Journal of Anatomy
(Dec 2008)
• How Reliable Are Human Phylogenetic Hypotheses? - PNAS (Jan 2000)