First Man?: The Orrorin Debate

In parts of Kenya, hominid fossils are found surprisingly often.  The discovery of Orrorin tugenensis in the region, thus, has not been surprising for its location, but for its content and how it will be interpreted by different archaeologists.  Brigitte Senut, a French paleoanthropologist, found the fossils and has declared some rather radical abilities for Orrorin.  Senut and her colleague, Martin Pickford, have advanced some hypotheses that, most likely, will not stand to future evidence.  Despite the importance of these fossils and the creature the bones once belonged to, Senut and Pickford are probably wrong when they claim for Orrorin the position of direct ancestor to humans.

Senut and her team were working in Kenya, in the Lukeino Formation of the Tugen Hills.  Over all, they found twelve fossils; “including fragmentary thigh and arm bones as well as several teeth” (Aiello and Collard: 526).  Along with a molar that had actually been discovered in the 1970s, they dubbed this new species Orrorin tugenensis.

The researchers claim that the fossils are around six million years old, which has been backed up by the geology that surrounded the fossils.  However, they also claim that their Orrorin is a direct ancestor of man.  They reposition Ardipithecus ramidus, which is now thought by many in the scientific community to be the first known human ancestor, to the position of ancestor of the African apes (Aiello and Collard: 527).  Senut also argues that, based on the fossil evidence of all the hominins, there is a “very old division in hominin locomotor ability” (Aiello and Collard: 527).  Through this, she places Orrorin in the human past because she believes that it probably walked very similar to how later hominins leading to humans walked.

Senut bases these interpretations on the upper thigh bone.  According to Aiello and Collard, “she [Senut] and her colleagues argue that the head of the thigh-bone is very large and human-like in relation to the size of the neck of the bone” (527).  She also bases Orrorin’s human-ancestor status because the enamel on their smaller molars is thick, like that of humans.  Most other hominins have larger and less-enameled molars.

If Senut’s position is true, it would mean that ancestor lines for the various groups of human-like creatures have been arranged incorrectly.  This would mean that we would have to look at these different traits that Senut places an emphasis on, such as walking type, in order to get the human family tree in order.  As Aiello and Collard point out, paleoarchaeologists have traditionally used similarities in the skull and teeth to draw connections between hominins (527).

The discovery also means that scientists are closer than ever to finding the common ancestor between humans and the African apes.  Orrorin is a full six million years old.  The range of time for the last common ancestor for the two groups is five to eight million years ago.  Even if this particular species is not the connector, we are more aware of what hominins looked like and what their development level is going to be.

Before Orrorin, the oldest hominins known to science were around four and a half million years old; quite old, but not quite old enough to be really one of the first species from the split between humans and apes (Aiello and Collard: 526).  Orrorin is quite a bit closer in time to that point, and the specimen may give us clues as to how and why the two groups separated in the first place.

Even if Senut is wrong about the layout of the human family tree, Orrorin still gives us perspective on human development and shows us that human fossils from the time period have survived the age, and it is possible to obtain more information on hominins that lived during that time.  As Henry Gee states, “fossil evidence of human evolutionary history is fragmentary” at best, and it is difficult to keep in mind that the information we have now could be made obsolete by further discoveries on this or other hominin species (131).  And that could occur at any point.

However, it appears that Orrorin is a very primitive hominin at best.  In fact, as Gee explains, “some of the fossils currently described as hominid may be more akin to chimpanzees, or may represent an entirely extinct offshoot of the ancestry of hominids and chimpanzees” because of their close temporal relationship with the human-African ape common ancestor (131).  So, it is even possible for this particular species to be an offshoot of the common ancestor and to not even have had a hand in human or ape evolution.  It is certainly good to keep this in mind, because it seems that Senut and her colleagues have been in a rush to establish their finds as a guaranteed direct human ancestor.  It certainly appears that, in their hurry to get their fossilized hominin in the lineage, they have ignored the fact that Ardipithecus ramidus has been considered a good candidate for the line that leads directly to humans, and that there is little, if any, evidence that links Ardipithecus with the African ape line, and that the evidence that directly links Orrorin with humans is tenuous at best.

Senut’s usage of different variables from most paleoanthropologists to classify position and relationships between hominins is shaky.  To not use the head and face to determine where species may have fit is odd.  An examination of how Orrorin would fit if it were examined in a more typical fashion should be done.  When it is, I think Orrorin will most likely not be a direct human ancestor, but instead off to the side, perhaps as a root for the Australopithecines instead.

I do not think that the interpretation that Brigitte Senut and her colleague, Martin Pickford, give to Orrorin should be the main one considered when thoughts turn to the fossils.  Pickford has long had problems with the Leakeys, a pre-eminent family in the field of hominid paleontology.  The Leakeys are very strong in Kenya; they have run the National Museums of Kenya, with which one must be affiliated in order to do fossil digs in Kenya (Butler: 508).  There has been an ongoing rivalry between Richard Leakey and Pickford over rights to fossil sites in Kenya, which are considered to be some of the best for hominin fossils.  Currently, Pickford is suing Leakey for causing his arrest when found to be digging with an expired permit (Butler: 509).

The charges against Pickford were dropped, and he was allowed to continue working with Senut.  However, now there is a claim from Andrew Hill, the chair of the anthropology department at Yale, claims that Pickford encroached on his permitted area in Tugen Hills (Butler:  508).  Senut and Pickford claim that they made inquiries with the government and visited the area to make sure that there was no one else who was working there at the time.  As was quoted by Butler: “‘It is very difficult to know who is telling the truth’” (509).

The feeling I get from this situation is that, despite the importance of the Orrorin fossils, Pickford and Senut are misrepresenting them in order to further their own interests.  Pickford, especially, has a habit of needling personal animosities.  In 1995, he co-wrote a book called Richard E. Leakey: Master of Deceit (Butler: 509).  This willingness to publicly attack a perceived enemy may take more than one form.  Pickford may have seen an opportunity to embarrass Leakey by discovering the direct ancestor of modern humans in an area where Leakey had tried to kick him out of!

Senut may believe that Orrorin is a precursor to humans, but the truth is that the public image of both Senut and Pickford are boosted because they have claimed to find the oldest known hominin.  Both have to know that the claim that the creature is directly related to humans is very controversial, and I think that they expected conflict over the designation.  But what is there to lose over such a conjecture?  There will have to be more discoveries to be able to say one way or the other with any degree of certainty whether Orrorin is even a hominin.  It could be that it is more closely related to chimpanzees.  But until that data has been found and analyzed, hypothesizing based on observation and measurements can be used instead.

It does appear to me that the people involved with the discovery have shaped the outcome of the conclusion that was reached regarding these fossils.  Good science is always done with the most objective outlook possible, and it does not appear that Martin Pickford could have kept the best view possible because of his arrest and problems attached to this dig.  The subjective view he had could have ranged from deliberate manipulation of the data to just wanting to make the best out of a bad situation.

This is not to say that the discovery of Orrorin is in some way less important if it is not a direct relation to humans.  On the contrary, it is remarkable to see what diversity there was in the development of hominins.  Orrorin is remarkable because it is a very old hominin – it is very close to the time when the human branch split off from the African ape branch.  That makes it something very important indeed – perhaps one of the very first hominins to come from the common ancestor of both chimpanzees and humans.

However, I think that the interpretations that have been given the fossils by Senut and Pickford were given due to the unconventional analyses used and the possible political gains to be had.  Would Senut and Pickford have advanced Orrorin as the direct ancestor of man if Pickford had not had the problem with the Leakeys?  Maybe, but I don’t think it would have been advanced as strongly.  This is a case of science being secondary to personal positions, I think.  Orrorin would be better treated if examined by many scientists and then a conclusion was reached.

Works Cited

Aiello, Leslie C. and Mark Collard.  “Our newest oldest ancestor?”  Nature 29 March 2001: 508-9.

Butler, Declan.  “The battle of Tugen Hills.”  Nature 29 March 2001: 526-7.

Gee, Henry.  “Return to the planet of the apes.”  Nature 12 July 2001: 131-2.


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