“Horned” crocodile may have preyed upon prehistoric humans

A Cuban crocodile (Crocodylus rhombifer), photographed at the National Zoo in Washington, DC.

No one knew what happened to William Olson. At about three in the afternoon on April 13, 1966 he had been swimming with his friends from the Peace Corps in the part of the Baro river that ran through Gambela, Ethiopia when he suddenly disappeared. The last person to remember seeing him was hunter Karl Luthy. One moment Olson was standing in the river, pressing his body against the current, and the next he was gone.

Luthy could not be sure, but he was almost certain that Olson had been taken by a Nile crocodile. He and the people who lived in the nearby village had warned the young travelers that swimming in the river was dangerous, especially since a child and a woman had been recently devoured by a crocodile there, but the American visitors did not care. Luthy’s fears were confirmed about a half hour after attack. Just at the edge of sight the crocodile appeared with Olson’s body in its jaws, but rather than go after the animal right away Luthy decided to wait until morning. Rushing to kill the reptile would do no good. Olson was already dead, and if Luthy attempted to shoot to crocodile while it was still in the river both the animal and Olson’s body might be lost. Instead he decided to leave the predator be until morning when it came out of the water to bask in the sun.

The crocodile did just as Luthy predicted. It hauled itself out onto the riverbank at about seven the next morning, and after a few attempts Luthy and his client were able to kill it. When they opened it up there could be no doubt that the thirteen-foot long crocodile was the one that had killed Olson. What was left of the young man was placed in a cardboard box.

Such tragic events remind us that we are not separate from or above nature. Much like our hominin forebears we can still be prey, and crocodiles are among the animals that have long considered us to be on the menu. Fragmentary remains of fossil hominins from the famous locality Olduvai Gorge, especially, show tell-tale signs that crocodiles consumed the bodies of our ancient relatives, and new fossils from the 1.8 million year old rocks there have identified one of the possible culprits.

A restoration of a Nile crocodile skull (top) compared to a preliminary restoration of a C. anthropophagus skull based upon available evidence.

For years it had been assumed that the Olduvai crocodiles were prehistoric representatives of the Nile crocodiles (Crocodylus niloticus) that still occasionally snatch people from the water’s edge, but when crocodile expert Chris Brochu looked at numerous fragments collected by Jackson Njau and Robert Blumenschine he realized that the Olduvai croc was something quite different. Even though he had only a collection of fragments to work with the paleontologists could tell that this ancient reptile had a deeper snout than its living relative, and the back of its skull was flared up into “horns” of bone that would have given it a unique profile somewhat reminiscent of living Cuban crocodiles (Crocodylus rhombifer). This prehistoric croc would have dwarfed all but the largest of its living relatives, though. Estimated at a maximum length of approximately 25 feet long it would have been a truly frightening ambush predator, and given the tooth-marked hominin bones the the trio of scientists decided to name it Crocodylus anthropophagus in the journal PLoS One.

Clearly C. anthropophagus was large enough to kill and consume hominins, but did it really do so? To approach an answer we have to split this question into two. From the fossil evidence collected so far it is clear that some prehistoric crocodiles at Olduvai consumed the bodies of hominins. Tooth marks on hominin bones confirm this beyond reasonable doubt.

Lower jaw fragments of the newly-named crocodile Crocodylus anthropophagus. From the PLoS One paper.

The question is whether individual C. anthropophagus killed the hominins in the first place. On this point there is no evidence to discuss. It is certainly plausible that C. anthropophagus counted early humans as prey but given the present lack of direct evidence actual predation is difficult to confirm. Even so it is remarkable that we have any evidence that these crocodiles fed on hominins at all. Large C. anthropophagus individuals probably would have pulverized hominin bodies prior to consumption, and once the flesh and bones of the early humans entered the crocodile’s stomach they would be eaten away by powerful stomach acids. (As the authors suggest this means that smaller crocodiles fed upon the hominins represented by the tooth-marked bones.) If hominins fell prey to fully-grown crocodiles it is unlikely that any trace would have been left behind.

These caveats aside I do think it is likely that C. anthropophagus at least occasionally fed on hominins. Given the projected size of the crocodile, the habits of its living relatives, and the tooth-marked bones I do not think that a C. anthropophagus would not have much hesitation about gobbling up an unwary hominin if the opportunity presented itself. While we might consider Olduvai to be one of the cradles of our ancestors, a place where stone tools were invented and utilized, 1.8 million years ago the human inhabitants of that place were still prey.

[The account of Olson’s death was summarized from a fuller account given in the book Eyelids of Morning: The Mingled Destinies of Crocodiles and Men]

Brochu, C., Njau, J., Blumenschine, R., & Densmore, L. (2010). A New Horned Crocodile from the Plio-Pleistocene Hominid Sites at Olduvai Gorge, Tanzania PLoS ONE, 5 (2) DOI: 10.1371/journal.pone.0009333