Stone Tools May Be Crocodile Stomach Stones
“Were crocodiles responsible for the stones we call tools?” is the title of a surprising letter to the editor in Nature last week.1 Patrick Dempsey (the archaeologist, not the actor) raised a possibility that paleoanthropologists and the journals have been making a big mistake for a long time. He asked, “Could Nature have been unknowingly publishing papers for the past 80 years about crocodilian gastroliths (stomach stones) instead of stones concluded to be 2.5-million-year-old hominid tools?”
Surely anthropologists have thought of this and know how to tell the difference, right? “Palaeontologists use a simple eyeball test to distinguish stone tools from gastroliths,” Dempsey said. If there are only wear marks on the outer surface, it’s a gastrolith. “But wear on both inner and outer surfaces indicates that it has been used for some sort of pounding or battering and can confidently be considered a tool.” That’s the thinking, but Dempsey stared at photographs from a recent paper in Nature by 18 scientists claiming stones from Africa were tools,2 and noticed the stones only had wear on extended surfaces. These were not tools. According to him, they had been tumbling inside some crocodile stomach for awhile. How could so many scientists be mistaken?
Identification of the Oldowan specimens as tools is based on the fact that the soft relict sands of Olduvai Gorge contain no natural stones of their own, so any stone found there must have been moved from distant river beds by some unknown animal transporter – concluded by high science to be Homo habilis. But crocodiles have the curious habit of swallowing rocks: these account for 1% of their body weight, so for a 1-tonne crocodile that’s 10 kg of stones in its stomach at all times. Surprisingly, science has never even considered the crocodile as transporter.
Homo habilis is nicknamed “Handy man” by evolutionary anthropologists because of assumed evidence he was a toolmaker. Dempsey’s scenario for the tool evidence, however, pictures crocs on ancient riverbeds vomiting up their gastroliths with no handymen in sight. “Hippo herds would naturally trample riverside gravel stones into the shape of Oldowan cutting tools, quantities of which the crocodile would then swallow and transport to other places.” The stones were deposited at the river edge where the crocodiles lived and died.
So far, all East African Oldowan specimens have come from the same waterside environments where crocodiles are known to have dwelt. Millions, perhaps trillions, of transported crocodile stomach stones must remain where the old crocodiles left them, deep in relict East African sediments, though none has ever been reported.
A quick Google search does not reveal any response to this letter yet. A future issue of Nature will undoubtedly contain rebuttals – probably from the 18 anthropologists accused of misidentifying the Oldowan stones. The point is that science needs to be open to alternative interpretations of mute historical evidence. The fact that Nature published this letter and even dressed it up with a Sidney Harris cartoon of a croc ordering stones at a fast-food counter indicates that the editors felt Dempsey’s letter deserves a response. We’ll have to wait and see if that comes after awhile, crocodile.
1. Patrick Dempsey, “Were crocodiles responsible for the stones we call tools?” Correspondence, Nature 461, 341 (17 September 2009) | doi:10.1038/461341a; Published online 16 September 2009.
2. Haslam et al, “Primate archaeology,” Nature 460, 339-344 (16 July 2009) | doi:10.1038/nature08188.
3. Recently, Dempsey also questioned interpretations of “stone tools” in the California desert by the late great Louis Leakey. His publication by the SCA Society alleges they were products of lightning spalls at the same location that had been reported in a scientific paper 25 years earlier. The fact that a famous scientist could be so mistaken is what led him to also question the stone tool interpretation at Olduvai Gorge.
We’re not taking sides till the rebuttals are in, but wouldn’t it be funny if the paleoanthropologists in “high science” have been goofing for 80 years? Actually, it’s not so funny if our children have been told falsehoods about Homo habilis for the last four generations. The evolutionary storytellers are likely to be upset with this upstart “Great Basin avocationalist” throwing stones into their glass house. They will need to preserve their reputations as much as the evolutionary Myth of Handy Man evolving into Man the Wise.
What can we learn from this story? For one, stones do not interpret themselves. It takes a fallible human to put them into an artificial explanatory framework. Other fallible humans can look at the framework to see how well the evidence fits, but fallible humans make mistakes (by definition). Second, scientists sometimes get on bandwagons. They train each other and learn how to interpret the evidence according to the reigning paradigm. The paradigm can become self-reinforcing. Science needs observers outside the box who aren’t affected by bluffing and peer pressure. Third, evolutionists have been caught again using design detection principles in spite of themselves, but this time, they may have reported a false positive. Fourth, where indeed are the trillions of gastroliths that should be there if this site was inhabited by crocs and hippos for millions of years?
Finally, some paradigms can become so intransigent that contrary evidence may not dislodge them. In the cartoon strip Peanuts, Lucy was showing Charlie Brown a butterfly on the sidewalk one day. She explained that butterflies this large usually are found in Brazil. Looking closer, Charlie Brown exclaimed, “That’s no butterfly, it’s a potato chip!” to which Lucy responded, “Well I’ll be, you’re right, Charlie Brown. I wonder how a potato chip got all the way here from Brazil?”
If the paleoanthropologists come to agree with Dempsey that the Oldowan stones are indeed gastroliths, they will not likely apologize for 80 years of mythology about Homo habilis. They will just merge the antithesis into a new synthesis. They will claim that the Handy Men were so handy, they even kept crocodiles as pets and harvested their gastroliths to use as tools. An alternative interpretation might be the classification of a new genus, Crocodylus habilis. Irrefutable complicity; wouldn’t that be a handy crock.