The ecosystems of eastern Africa, roughly 18 million years ago, included a wide diversity of life, much of which gave rise to major animal groups still living in the area today. This included some of the earliest human ancestors, who evolved within a complex and thriving food web. One key component in that backdrop were the crocodilians, predators who would have held real significance for the other animals in their environment. Today, these animals are known to exhibit aggression toward each other, but the antiquity of that behavior has been difficult to study. We had a rare opportunity to study this behavior through the incredible and dense crocodilian fossil deposit called Nyang Rise, on Rusinga Island in western Kenya. The site was initially excavated in 2011 and it became clear that crocodilians were the most abundant animal represented. Many of these bones also exhibited pathological features largely stemming from injuries likely incurred by other members of their species. One of the primary ways crocodilians manage to occupy the same environment without overcompeting comes from a form of social aggression where non-fatal bites are inflicted, often from larger to smaller individuals. These frequently leave clear marks on the bones with signs of healing. The high concentration of crocodilian remains and known commonness of the pathologies made this site in particular an exciting chance to study this form of behavior, 18 million years ago. However, due to changing land use conditions, the site became under threat for housing development in 2023.

Thanks to funds from the National Science Foundation (NSF), a team was assembled to carry out a three week excavation and recover as much fossil material as possible, while retaining critical location data. The team included two US citizens, professional paleontologists, and a total of 21 residents of Kenya. Two of the Kenyan members of the team are staff at the National Museums of Kenya (NMK) in Nairobi, which serves as the national repository for fossils. Kenya maintains strict regulations that no fossils are allowed to leave the country and that all fossil material found in the country should ultimately be held at NMK. As such, we were very glad to have staff with us on the excavation. We excavated in quarry squares, documenting precisely where each fossil was found and in what orientation. At the end, we transported all material to NMK along with all records and shared copies of all field photos. Over the next 11 months, the team at NMK processed this material, conducting all necessary stabilizing preparation and storage of specimens. All material is now safely held in the collections and is accessible for study.

The project was highly successful, recovering over 10,000 fossil specimens. By far the most common animals were the crocodilians. Many indeed exhibited pathologies stemming from aggression. The high crocodilian concentration (and therefore aggression) may be explained in part by the signs of desiccation in adjacent sediment layers, which may have concentrated aquatic animals (i.e. crocodilians) and led to heightened competition for resources. In addition to crocodilians, we recovered remains from relatives of hippos, giraffes, hyaenas, chameleons, turtles, fish, and more. We also recovered teeth of two individuals of Ekembo, an early human ancestor. This collection now serves as an incredibly rich resource for scientific information across the ecosystem, from which many additional lessons can be learned.

In total, 19 individuals from the island received payment for their assistance with the project and gained new skill sets. This helped forge new relationships between scientists and local residents as well as instill the value of these fossils that are from their community. We also held an outreach event at a local school, where we spoke with a large class of about 60 students. We showed them some of the fossils we found, what we were learning about them and what they should do if they find any. We then gave a second presentation to adults of the community (about 50 individuals), and left a lengthy amount of time for questions each time. Both presentations were made in the local language, Luo, thanks to one of the team members being particularly fluent in both Luo and English. Local members of the excavation also presented at a festival on Rusinga Island in December of 2023 with a table of fossil casts, and spoke about the work that was done at Nyang Rise. Videos and photos about the project were shared out on social media, with consent, in a 12 part series (Instagram and TikTok, @dr_crocogator), one of which was viewed more than 260,000 times.

It became abundantly clear that this is a deeply rich site. The thousands of fossils are worthy of extensive study, and as such we anticipate research publications stemming from this collection to unfold for many years to come.

Last Modified: 12/24/2024
Modified by: Alexander Hastings