Prehistoric Otter

In terms of Mammalian evolution, the great apes (or “Hominidae”) are a recent development. They first appeared around 13-15 million years ago in the Miocene period and would go on to diversify into a variety of different species. Among these are, of course, the various species of human, including the only surviving one, our own (Homo sapiens). This one member of the great ape lineage now has a population of roughly 7 billion, lives across the entire globe, and has changed the landscape of the earth to such an extent that many geologists think that this modern age is its own distinct geological period (known as the Anthropocene). But to understand the earliest evolution of the great apes (and by extension our own species) studies must be made of the often fragmentary remains of these first apes. One such ape was discovered in 2004 in the Catalonia region of Spain. This species is Pierolapithecus catalaunicus.

The name Pierolapithecus catalaunicus comes from the village where the first fossils were discovered: “Els Hostalets de Pierola”. These first finds consisted of cranial (the top of the skull) and postcranial (the back of the skull) elements as well as some isolated teeth. Moving down, further remains were found of the thorax (chest and pelvis), lumbar region (the lower spine near the hips) and the wrist. Reconstructions from these remains estimate that it wouldve weighed around 55 kilograms, around the same as a female chimp. Studying these bones and further finds gave paleontologists clues as to how Pierolapithecus may have lived. For example, the structure of the wrist, thorax and lumbar bones suggests that Pierolapithecus would have spent most of its life in the trees, rather like the modern-day Orangutan.

Pierolapithecus is hypothesized to be a basal (or early) member of the great apes, but while it can be identified as one (e.g. it shared the same facial pattern as modern great apes, with a particularly Gorilla like face), it had yet to evolve all of their features (e.g. their fingers are not like great apes). Think of it as a kind of transitional form, or to use the overused (and misleading) term “missing link”, between the great apes and the “lesser apes” (i.e. Gibbons and Siamangs). Dating of the sediments around the bones indicate that they were roughly 12.5-11.9 million years old, putting Pierolapithecus in the middle of the Miocene period and suggesting that it was one of the oldest of the great apes. These bones also possess marks made by carnivores, indicating that they were either scavenged, or that there were active predators that Pierolapithecus had to watch out for.

Another feature that links Pierolapithecus to great apes is that it is thought to have had orthogrady. This term describes an animal that walks upright on its hind legs, with its spine curved partly upright, for long periods of time. Further, Pierolapithecus’ patella bone (a bone found on the upper knee) is like modern great apes and allows mobile movement of the knee. Combined with its moderately sized hands and a broad and shallow thorax, it suggests that Pierolapithecus was adapted more for vertical climbing and movement rather than suspending and couldn’t swing between branches. This is certainly weird considering that some modern great apes, like Chimpanzees, can swing. Therefore the ability to swing between branches must have evolved multiple separate times in great apes, and isn’t an ancestral trait. Another implication is that if a mostly tree dwelling animal possessed orthogrady then maybe upright walking didn’t originate just for walking on the ground. Instead orthogrady would have been used for walking along the branches of trees first before later being co-opted for a terrestrial lifestyle in humans their closest ancestors. One advantage of this is that it would have freed up Pierolapithecus’ arms to reach and grab ripe fruit and leaves that were previously out of reach.

But where on the great ape family tree was Pierolapithecus? well it is debated whether it is a basal hominid (e.g. ancestral to all living great apes) or a basal hominin (e.g. ancestral to humans, chimps, bonobos and gorillas only). Evidence that supports it being a basal hominid include a study in 2012 (Pérez de los Ríos, Moyà-Solà & Alba 2012) that analysed areas of the skull including the pneumatic structures, nasal area and palate. This analysis showed that these features were intermediate between basal hominoids and pongines (the ape family that contains Orangutans), and therefore that Pierolapithecus was more hominid than hominin. This study seems to have put the hominid idea in the driving seat, but if Pierolapithecus were to be a basal hominin, and on the line that produced humans and their close relatives then this raises another interesting possibility. It is often thought that all early hominid and human evolution took place within Africa. Then human relatives, and humans themselves, migrated out of Africa and spread to new lands in Europe, Asia and (in the case of humans) the rest of the world. However, Pierolapithecus was discovered in the Catalonia region of Spain! If the early human ancestor that Pierolapithecus is closely related to also lived in Europe then early human ancestors must have migrated from Southern Europe into Africa, where they would then continue to evolve and produce multiple human species, and humans themselves. In short, our very earliest ancestors may have originated in Europe, not Africa! Of course, this is just a theory and further fossil evidence from other stem hominids is required to prove or disprove it. It is equally plausible that Pierolapithecus may be an outlier, a side branch of stem hominids that migrated from Africa into Southern Europe while the early human ancestor lived in Africa. It is also possible that the range of Pierolapithecus would have extended into Africa too, we just have only found their remains in Spain at the moment. We cannot be sure right now, but it is a fascinating possibility!

Pierolapithecus, this seemingly unassuming great ape from Spain, is certainly an intriguing primate and a key piece of unlocking the puzzle box that is figuring out how this great, and eventually world changing, lineage came to be.

References/Further Reading

• Moyà-Solà et. al. 2004: the paper that first described Pierolapithecus catalaunicus

Moyà-Solà, S., et al. (2004). “Pierolapithecus catalaunicus, a New Middle Miocene Great Ape from Spain.” Science 306(5700): 1339-1344.

• Crompton, Vereecke & Thorpe 2008: a paper that described locomotion and orthogrady/pronogrady movement among early stem hominids.

Crompton RH, Vereecke EE, Thorpe SK. Locomotion and posture from the common hominoid ancestor to fully modern hominins, with special reference to the last common panin/hominin ancestor. J Anat. 2008 Apr;212(4):501-43. doi: 10.1111/j.1469-7580.2008.00870.x. Erratum in: J Anat. 2008 May;212(5):703. PMID: 18380868; PMCID: PMC2409101.

• Hammond et. al. 2013 paper, published in the Journal of Human Evolution, on the pelvic morphology of Pierolapithecus and comparisons with other stem hominids

Ashley S. Hammond, David M. Alba, Sergio Almécija, Salvador Moyà-Solà, Middle Miocene Pierolapithecus provides a first glimpse into early hominid pelvic morphology, Journal of Human Evolution, Volume 64, Issue 6, 2013, Pages 658-666, ISSN 0047-2484, https://doi.org/10.1016/j.jhevol.2013.03.002.

• Nakatsukasa 2019 paper on the spinal morphology of Miocene apes like Pierolapithecus and the evolution of Orthogrady

Nakatsukasa M. (2019) Miocene Ape Spinal Morphology: The Evolution of Orthogrady. In: Been E., Gómez-Olivencia A., Ann Kramer P. (eds) Spinal Evolution. Springer, Cham. https://doi.org/10.1007/978-3-030-19349-2_5

• Pina et. Al. 2014 paper on the structure of Pierolapithecus’ knee bones in relation to its skeleton, and what can be inferred about its climbing and swinging ability

Pina M, Almécija S, Alba DM, O’Neill MC, Moyà-Solà S (2014) The Middle Miocene Ape Pierolapithecus catalaunicus Exhibits Extant Great Ape-Like Morphometric Affinities on Its Patella: Inferences on Knee Function and Evolution. PLoS ONE 9(3): e91944. https://doi.org/10.1371/journal.pone.0091944

• Pérez de los Ríos, Moyà-Solà & Alba 2012 paper that examined the skull areas containing the nasal region, pneumatic structures and palate. Their study provides evidence that Pierolapithecus is a basal hominid.

Miriam Pérez de los Ríos, Salvador Moyà-Solà, David M. Alba, The nasal and paranasal architecture of the Middle Miocene ape Pierolapithecus catalaunicus (primates: Hominidae): Phylogenetic implications, Journal of Human Evolution, Volume 63, Issue 3, 2012, Pages 497-506, ISSN 0047-2484, https://doi.org/10.1016/j.jhevol.2012.05.012.