Can we be certain about something that happened half a million years ago?
Keith S. Taber
About half a million years ago a hominid, of the Homo erectus species, living in Java took a shell and deliberately engraved a mark on it. Now, I was not there when this happened, so my testimony is second hand, but I can be confident about this as I was told by a scientist that she was sure that this definitely happened.
"…we knew for sure that it must have been made by Homo erectus"
But how can we be so sure about something alleged to have occurred so long ago?
I doubt Fifi would be convinced.1 Fifi was a Y12 student (c.16 years old) interviewed as part of the LASAR project who had reservations about palaeontology as it did not provide certain scientific knowledge,
"I like fossils though, I think they're interesting but I don't think I'd really like [working as a palaeontologist]…I don't think you could ever really know unless you were there… There'll always be an element of uncertainty because no matter how much evidence you supply there will always be, like, doubt because of the fact that you were never there…there'll always be uncertainty."
Fifi quoted in Taber, Billingsley & Riga, 2020, p.57
Learners can have alternative conceptions of the nature of science, just as much as they often do for forces or chemical bonding or plant nutrition. They often think that scientific knowledge has been 'proved', and so is certain (e.g., Taber, Billingsley, Riga & Newdick, 2015). An area like palaeontology where direct observation is not possible may therefore seem to fall short of offering genuine scientific knowledge.
The uncertain nature of scientific knowledge
One key feature of the nature of science is that it seeks to produce general or theoretical knowledge of the natural world. That is, science is not just concerned with providing factual reports about specific events but with developing general accounts that can explain and apply to broad categories of objects and events. Such general and theoretical knowledge is clearly more useful than a catalogue of specific facts – which can never tell us about the next occasion or what might happen in hypothetical situations.
However, a cost of seeking such applicable and useful knowledge is that it can never be certain. It relies on our ways of classifying objects and events, the evidence we have collected so far, our ability to spot the most important patterns -and the deductions this might support. So, scientific knowledge is always provisional in the sense that it is open to revision in response to new data, or new ways of thinking about existing data as evidence.
Read about the nature of scientific knowledge
Certainty and science in the media
Yet often reports of science in the media give the impression that science has made absolute discoveries. Some years ago I wrote about the tendency in science documentaries for the narrative to be driven by links that claimed "...this could only mean…" when we know that in science the available data always underdetermines theory (Taber, 2007). Or, to put it another way, we could always think up other ways of explaining the data. Sometimes these alternatives might seem convoluted and unlikely, but if we can suggest a possible (even when unconvincing) alternative, then the available data can never "only mean" any one particular proposed interpretation.
Read about scientific certainty in the media
Fossils from Java
Prof. Joordens who reported on how a shell had been deliberately marked by a member of the Homo erectus species hundreds of thousands of years ago.
(taken from her website at https://www.naturalis.nl/en/science/researchers/jose-joordens )
The scientist concerned was J.C.A (José) Joordens who is Professor in Hominin Paleoecology and Evolution, at Maastricht University. Prof. Joordens holds the Naturalis Dubois Chair in Hominin Paleoecology and Evolution. The reference to Dubois relates to the naturist responsible for finding a so-called 'missing link' in the chain of descent to modern humans,
"One of the most exciting episodes of palaeoanthropology was the find of the first transitional form, the Pithecanthropus erectus, by the Dutchman Eugène Dubois in Java during 1891-1892. …Besides the human remains, Dubois made a large collection of vertebrate fossils, mostly of mammals, now united in the so-called Dubois Collection."
de Vos, 2004
The Java man species, Pithecanthropus erectus (an upright ape/mokey-man), was later renamed as Homo erectus, the upright man.
On an edition of BBC Radio 4's 'In Our Time' taking 'Homo erectus' as its theme, Prof. Joordens explained how some fossil shells collected by Dubois as part of the context of the hominid fossils had remained in storage for over a century ("The shells had been, well, shelved…"!), before a graduate student set out to photograph them all for a thesis project. This led to the discovery that one of the shells appeared to have been engraved.
This could only mean one thing…
This is what Prof. Joordens told the host, Melvyn Bragg,
"One shell that had a very strange marking that we could not understand how it ended up there…
It was geometric, like a W, and this is of course something that animals don't produce. We had to conclude that it must have been made by Homo erectus. And it must have been a very deliberate marking because of, we did experimental research trying to replicate it, and then we actually found it was quite hard to do. Because, especially fresh shells, they have a kind of organic exterior, and it's hard to push some sharp objects through and make those lines, so that was when we knew for sure that it must have been made by Homo erectus."
Prof. José Joordens talking on 'In Our Time'
We may consider this claim to be composed of a number of components, such as:
- There is a shell with some 'very strange' markings
- The shell was collected in Java in the nineteenth century
- The shell had the markings when first collected
- The markings were not caused by some natural phenomenon
- The markings were deliberate not accidental
- The markings were made by a specimen of Homo erectus
A sceptic might ask such questions as
- How can we be sure this shell was part of the original collection? Could it have been substituted by mistake or deliberately?
- How do we know the marks were not made more recently? perhaps by someone in the field in Java, or during transit form Java to the Netherlands, or by someone inspecting the collection?
- Given that even unusual markings will occur by chance occasionally, how can we be certain these markings were deliberate? Does the mark really look like a 'W 'or might that be an over-interpretation. 2
And so forth.
It is worth bearing in mind that no one noticed these markings in the field, or when the collection was taken back to the Netherlands – indeed Prof. Joordens noted she had carried the shell around in her backpack (could that have been with an open penknife?) unaware of the markings
Of course, Prof. Joordens may have convincing responses to many of these questions – but a popular radio show is not the place to detail all the argument and evidence. Indeed, I found a report in the top journal Nature ('Homo erectus at Trinil on Java used shells for tool production and engraving') by Prof. Joordens and her team 3, claiming,
"One of the Pseudodon shells, specimen DUB1006-fL, displays a geometric pattern of grooves on the central part of the left valve [*]. The pattern consists, from posterior to anterior, of a zigzag line with three sharp turns producing an 'M' shape, a set of more superficial parallel lines, and a zigzag with two turns producing a mirrored 'N' shape. Our study of the morphology of the zigzags, internal morphology of the grooves, and differential roughness of the surrounding shell area demonstrates that the grooves were deliberately engraved and pre-date shell burial and weathering"
Joordens et al, 2015, p.229
[* Photgraphs are included in the paper. Some can also be seen at https://www.smithsonianmag.com/science-nature/oldest-engraving-shell-tools-zigzags-art-java-indonesia-humans-180953522/ ]
It may seem most likely that the markings were made by a Homo erectus, as no other explanation so far considered fits all the data, but theory is always under-determined – one can never be certain another scenario might be found which also fits the known facts.
Strictly, Prof. Joordens' contradicts herself. She claims the marks are "something that animals don't produce" and then claims an animal is responsible. She presumably meant that no non-hominid animal makes such marks. Even if we accept that (and, as they say, absence of evidence is not evidence of absence 4), can we be absolutely certain some other hominid might not have been present in Java at the time, marking the odd shell? As the 'In Our Time' episode discussed, Homo erectus often co-existed with other hominids.
Probably not, but … can we confidently say absolutely, definitely, not?
As Fifi might say: "I don't think you could ever really know unless you were there".
My point is not that I think Prof. Joordens is wrong (she is an expert, so I think she is likely correct), but just that her group cannot be absolutely certain. When Prof. Joordens says she knows for sure I assume (because she is a scientist, and I am a scientist) that this means something like "based on all the evidence currently available, our best, and only convincing, interpretation is…" Unfortunately lay people often do not have the background to insert such provisos themselves, and so often hear such claims literally – science has proved its case, so we know for sure. Where listeners already think scientific knowledge is certain, this misconception gets reinforced.
Meanwhile, Prof. Joordens continues her study of hominids in Java in the Studying Homo erectus Lifestyle and Location project (yes, the acronym is SHeLL).
Work cited:
- de Vos, J. (2004). The Dubois collection: a new look at an old collection. Scripta Geologica. Special Issue, 4, 267-285.
- Joordens, J., d'Errico, F., Wesselingh, F. et al. Homo erectus at Trinil on Java used shells for tool production and engraving. Nature 518, 228-231 (2015). https://doi.org/10.1038/nature13962
- Taber, K. S. (2007) Documentaries can only mean one thing, Physics Education, 42 (1), pp.6-7
- Taber, K. S., Billingsley, B., & Riga, F. (2020). Student perceptions of the knowledge generated in some scientific fields. School Science Review, 102(378), 65-70.
- Taber, K. S., Billingsley, B., Riga, F., & Newdick, H. (2015). English secondary students' thinking about the status of scientific theories: consistent, comprehensive, coherent and extensively evidenced explanations of aspects of the natural world – or just 'an idea someone has'. The Curriculum Journal, 1-34. doi: 10.1080/09585176.2015.1043926
Notes
1 As is usual practice in such research, Fifi is an assumed name. Fifi gave permission for data she contributed to the research to be used in publications on the assumption it would be associated with a pseudonym. (See: 'Using pseudonyms in reporting research'.)
2 No one is suggesting that the hominid deliberately marked the shell with a letter of the Roman alphabet, just that s/he deliberately made a mark that represented a definite and deliberate pattern. Yet human beings tend to spot patterns in random data. Could it just be some marks that seem to fit into a single pattern?
3 Josephine C. A. Joordens, Francesco d'Errico, Frank P. Wesselingh, Stephen Munro, John de Vos, Jakob Wallinga, Christina Ankjærgaard, Tony Reimann, Jan R. Wijbrans, Klaudia F. Kuiper, Herman J. Mücher, Hélène Coqueugniot, Vincent Prié, Ineke Joosten, Bertil van Os, Anne S. Schulp, Michel Panuel, Victoria van der Haas, Wim Lustenhouwer, John J. G. Reijmer & Wil Roebroeks.
4 At one time there was no evidence of 'noble' gases reacting. At one time there was no evidence of ozone depletion. At one time there was no evidence of superconductivity. At one time there was no evidence that the blood circulates around the body. At one time there was no evidence of any other planet having moons. At one time there was no evidence of protons being composed of even more fundamental particles. At one time there was no evidence of black holes. At one time there was no evidence that smoking tobacco was harmful. At one time there was no evidence of … [fill in your choice scientific discovery!]