Evolution, survival of the individual most likely to successfully adapt to changing environments and ecosystems.
Inevitably this leads to competition, competition between individuals, and competition between species. Competition is a keystone of evolution’s relentless progression and there are different types. The one we are going to look at here is the fight over who gets that tasty leaf. We see food fighting in the animal kingdom today very easily on TV but it is not so easy to see such competition in the Miocene.
Lasting from 23 to 5 million years ago, the “Miocene Series” was first named by the notable geologist Charles Lyell. Miocene comes from greek meaning “less recent”. Miocene primate evolution is not only less recent, relative to us today, but we know less about it relatively to the Pliocene series. Localities have not been to kind to revealing the primate fossils we need to understand Miocene primate evolution, but thankfully we have Rudabánya in the county of Borsod-Abaúj-Zemplén, north eastern Hungary. We will return to it later, but first….
It is incredible how little the general public know about this underappreciated series in earth’s history. I’d nearly adapt the lyrics of Michael Jackson’s Earth Song, lamenting that fact. Seems appropriate, right? Anyway, the “less recent” series is broken up into 6 faunal stages. So, what is a faunal stage?
Take the Serravallian Stage (13 – 11 Million Years Ago), for instance. Sphenolithus heteromorphus (a type of extinct plankton) only ever appeared in this stage and no other. A species or a number of species determines the boundaries of a faunal stage. What is the difference between then and now? Well, most organisms would look modern to you and I, but as the North American Miocene mammals demonstrate, there are subtle differences. Megapiranha, the genus, not the trashy movie, is a notable example. And now, back to Rudabánya.
Rudabánya enters the history books in the 19th century, when local collectors recovered mammalian fossils. Palaeoanthropologists really let out an excited wee in their pants when the very first hominoid mandible was collected by a local mining geologist. RUD 1 becomes the holotype for a new genus and species of hominoid, Rudapithecus hungaricus. Way to promote nationalism in the field of palaeoprimatology, eh!
The following decades have seen a great deal of fossils excavated including many primates. Anapithecus hernayaki was uncovered in 1972. These primates would have lived on a peninsula jutting into the (no longer existing) Pannonian Sea, 10 million years ago. Did these primates get along well together then? The latest paper examining these primates was not so quick to say for sure. This has to be one of my favourite papers because it proposes a hypothesis and sets out to test it. That is science. I could have just said I love science! Anyway, lets discuss this some more here.
How can we tease out the various sherds of evidence from fossils to find out whether or not two ape species were having a go at each other over food. Their diet and specifically their teeth can help unravel the mystery. Here we are looking at two geni, Rudapithecus hungaricus and Anapithecus hernyaki. Are they sympatric, then? Yes, arguably they are found within centimeters of each other in the stratigraphy.
Did they eat the same resources? To answer this we need to ask how they moved through the forest canopy? Looking at the arms and legs of these creatures they seem to be both adapted for suspensory locomotion, arguably using their arms more than their legs to move from branch to branch. Previous papers also suggest that Rudapithecus and Anapithecus differed from each other in body mass and tooth size. The latest paper sets out to clear up what these two geni ate. The question of whether or not these two fought it out over resources is somewhat of an after-thought in this paper. The teeth are essential points of reference and it is the upper jaw teeth (maxillary teeth), specifically 588 incisors that are put under the microscope here.
Now, we know a great deal about the diet of Rudapithecus, it have been studied to death. It would have preferred to eat soft fruits, with incisors used to peel off the hard outer skin (pericarp). Anapithecus is frustratingly difficult to pin down. It may have loved its leaves, but shearing quotients and microwear patterns tell you it loved its fruits. Anapithecus is the weakest link here, but palaeoprimatologists are not willing to say goodbye to it just yet (I do miss the Queen of Mean). If this investigation is going to continue we are going to need more evidence to support Anapithecus the leaf-lover or the fruit-lover.
No matter the preference of Anapithecus, it is highly likely it could have attempted to avoid competition. We see gorillas do the same today in Africa, relying more heavily on leaf resources compared with chimpanzees. But even if Anapithecus was a frugivore, it can be argued that the niche separation may not have been so stark, resulting in forest canopy position, microhabitat and group size differences. Now for the analysis details……………
On the left, is a hemi-mandible with the various teeth. The incisors are the only teeth we are interested in here. The first maxillary incisor is referred to as I1 (note the superscript), while the second maxillary incisor is referred to as I2 (again note the superscript). The sample includes 588 teeth from extant hominoids from the Gorilla gorilla gorilla (No, not a typing error) to the Ateles paniscus (Red-faced spider monkey).
The sample also includes our beloved fossil hominoids, Rudapithecus and Anapithecus. Representing the former are 7 I1 and 2 I2 teeth, while 6 I1 and 5 I2 represent Anapithecus. There were not enough mandibular teeth attributed to both species to warrant an analysis of mandibular teeth. All you need to know is when doing an analysis to investigate prehistoric diet it is good to include what we know with what we don’t know, in this case the well understood dietary patterns of modern primates with the less well understood fossil primates.
Discriminative function analysis (DFA) is a very useful form of predictive statistics that is very popular in palaeoanthropological research. Here, the computer is told what types the teeth need to be classified as i.e. folivorous or frugivorous. Taking into account morphology, the DFA then sets to work classifying the teeth. Rudapithecus I1 reveal the results we expected. It is frugivorous, but the I2 results classify both teeth as folivorous.
Now, yes, the sample of Rudapithecine I2’s leaves a lot to be desired. Issues with sample size aside, the team of palaeoprimatologists think that the DFA is bringing together hominoids both extant and extinct together based upon their peg-shaped lateral incisor similarities and actually says little about the diet of Rudapithecus. Anapithecus trends well as a folivore than a frugivore at the I1, but three out of the five I2 teeth suggest the opposite. It seems that the crown morphology of I2 cannot clearly identify which hominoid is folivorous or frugivorous. So, both primates have preferences, but dietary overlap is quite possible.
Rudapithecus may have eaten less preferred hard fruits when soft fruits were scarce, while Anapithecus ate soft fruits, relying upon leaves when the former was not available. The fossils are just not clear enough to say for sure what the diet of these extinct hominoids may have been. Let’s imagine Rudapithecus was eating soft fruits in spring, then competition is quite possible with Anapithecus. To test this we need a time machine. In its absence we have statistical analyses modern primates and plenty of debate. Together they make palaeoprimatology exciting every time.
Who would win a battle of the Hungarian Miocene Catarrhines? Rudapithecus may have weighted between 20 and 45 Kg, while Anapithecus may have weighed about 15 Kg. Based on size this is like pitching a Siamang (Symphalangus syndactylus representing Anapithecus) against a Bonobo (Pan paniscus representing Rudapithecus). The Siamang would turn tail. Could something similar be said for Rudapithecus and Anapithecus…………maybe but how do you test such a hypothesis? Some questions will remain unanswered.
Written by Charles T. G. Clarke