And now, you're wondering what I'm talking about.
The Claim: Paranthropus robustus was driven to extinction because its specialized "vegan" diet prevented it from adapting to changing climate. Or so I was recently informed by manowar40 in a YouTube comments section. His contention is that Homo was able to adapt to drying climate because of our omnivorous diets, while P. robustus was so dependent on a "vegan" diet that it died out.
It would be easy for me to dismiss this as just another misinformed omnivore on his high horse, but that's only because I'm a geek who reads paleontology journals. In other words, he doesn't follow all the latest research, and just relies on informed third parties to fill him in. And there's nothing wrong with that; it doesn't make him a dumbo at all.
It's just that his sources, whoever they are, are a bit behind the times.
True, it used to be the consensus that P. robustus died off because of a specialized diet. The reason for this assessment is that the paranthropines had big, flat, thick-enameled molar teeth and huge jaws, usually a sign of specialization to hard, brittle foods like nuts and seeds (hence, the nickname "Nutcracker Man," given to P. boisei, a close relative of robustus). Genus Homo has more generalized masticatory adaptations, reflecting a wider variety of food strategies.
Or so the reasoning used to go. That was before we started doing laser ablation stable isotope analysis, a method that allows us to analyze extremely small areas of carbonates and phosphates (on the order of 10 micrometers) in situ; that is, without having to crush and reprecipitate them. The method
allows for finer spot analysis than had been possible previously with traditional methods that required the homogenization of large amounts of material. The major advantages of this technique are that it is essentially nondestructive and requires little sample preparation.With the laser ablation method, we're able to not only tell what isotopes a fossil organism was absorbing from its food, but also get a pretty good idea what sorts of food it was eating over its life, because we can look at the actual wear patterns on its tooth enamel and correlate them with the isotope evidence over time and geography.
Doing this with the teeth of a P. robustus sample from Swartkrans, South Africa, Sponheimer et. al. reached a surprising conclusion (emphasis mine):
laser ablation stable isotope analysis reveals that the d13C values of Paranthropus robustus individuals often changed seasonally and interannually. These data suggest that Paranthropus was not a dietary specialist and that by about 1.8 million years ago, savanna-based foods such as grasses or sedges or animals eating these foods made up an important but highly variable part of its diet.They elaborated on the then-common idea that this species' extinction had been due to its presumed specialized diet (emphasis mine):
A dental microwear study of the earlier (3.0 to 3.7 Ma) hominin Australopithecus afarensis found no evidence that its diet changed over time or in different habitats (20). In contrast, stable carbon isotope (3, 4) and dental microwear texture analyses (1) of the slightly younger (~3.0 to ~2.4 Ma) hominin A. africanus demonstrated that its diet was far more variable. This suggests the possibility that a major increase in hominin dietary breadth was broadly coincident with the onset of increasing African continental aridity and seasonality after 3 Ma (21, 22) and only shortly antedated the first probable members of the genera Homo and Paranthropus (23–25) and the earliest stone tools (26). The undoubted toolmaker Homo is thought to have been a dietary generalist that consumed novel foods such as large ungulate meat and tubers that are abundant in savanna environments (27–30). Paranthropus, in contrast, with its extremely large and flat cheek teeth, thick enamel, robust mandible, and heavily buttressed facial architecture, is often portrayed as a dietary specialist (27–29). Further, it has been argued that this specialization contributed to its extinction when confronted with increasingly dry and seasonal environments later in the Pleistocene, whereas Homo’s generalist adaptation was crucial for its success (28, 29). Our results suggest that Paranthropus had an extremely flexible diet, which may indicate that its derived masticatory morphology signals an increase, rather than a decrease, in its potential foods. Thus, other biological, social, or cultural differences may be needed to explain the different fates of Homo and Paranthropus (31).In other words, their evidence suggested that both Paranthropus and Homo had inherited an omnivorous habit from their shared australopithecine ancestor. And further, that P. robustus' "specialized" teeth and jaws reflected not a restriction of its eating abilities, but an expansion of it.
This paper strengthened and confirmed a conclusion reached two years earlier by Wood & Strait:
We suggest that although the masticatory features of Paranthropus are most likely adaptations for consuming hard or gritty foods, they had the effect of broadening, not narrowing, the range of food items consumed. It is possible that these adaptations allowed Paranthropus to become a “seasonal specialist” by exploiting previously unavailable fallback food items during periods of dietary stress (Conklin-Brittain et al., 1988). One of us (e.g., Wood and Ellis, 1986), and many others, have wrongly interpreted the derived morphology of the masticatory system of Paranthropus as evidence for stenophagy. Instead, the vast majority of the evidence suggests that the masticatory system of Paranthropus is more consistent with euryphagy. Thus, the extinction of Paranthropus species should not be considered a straightforward consequence of having an overspecialized diet.Both papers have been cited fairly robustly (if you'll pardon the pun), and when I ask around among my anthro friends, it seems that this interpretation is shaping up to be the standard view of Paranthropus robustus.
What happened here is simple: whoever manowar40's been getting his paleo information from is behind the learning curve. That's not mano's fault, and it doesn't quite add up to an Idiotic Omnivore Claim because it's not exactly a claim that's detached from reality.
It just shows that scientists need to do a better job of communicating their work to the general public.