More than a century ago, a small group of chimpanzees helped revolutionize the way scientists understand intelligence. Through a series of pioneering experiments on the Spanish island of Tenerife, these apes demonstrated that they could solve problems using insight rather than relying solely on trial and error – a discovery that challenged long-held assumptions about the uniqueness of human reasoning.Yet, while their scientific achievements became famous, the fate of the chimpanzees themselves was largely ignored. According to Dr. Javier Virus-Ortega’s study, “The Fate of Sultan’s Clan,” published in the European Psychologist Journal, newly examined archival records reveal what happened to these famous chimpanzees after they were relocated to Berlin.
The chimpanzee that changed psychology
The Prussian Academy of Sciences established its anthropological research station in Tenerife in 1913, and the German psychologist Wolfgang Köhler served as its director from 1914 to 1920. During this period, he conducted pioneering experiments that would reshape the scientific understanding of animal intelligence.To answer this question, Kohler designed a series of experiments involving a group of chimpanzees that included Sultan, Rana, Chica, Grande, Tercera, and Tshego. Instead of teaching them by giving them repeated rewards, he presented them with unfamiliar problems that required planning and creativity. In one of the most famous experiments, bananas were hung out of reach while wooden boxes were scattered around the enclosure. Instead of making endless unsuccessful attempts, some chimpanzees stacked boxes to create a platform and climbed up to get to the fruit. Another historical experiment involved rods placed near food, beyond the reach of the animals. The Sultan famously realized that two short sticks could be joined together to create a longer tool capable of pulling food closer. These solutions appeared to emerge through sudden understanding, or “insight”, rather than gradual trial and error. These experiments became milestones in comparative psychology and helped establish that chimpanzees had sophisticated cognitive abilities, fundamentally changing scientific thinking about animal intelligence.
Skull of a chimpanzee named Rana-loka (Image credit: Javier Virus-Ortega via University of Auckland)
From scientific stars to forgotten lives
Although Köhler’s experiments became world famous, little attention was paid to the chimpanzees’ later lives.When the Tenerife research station closed in the 1920s, the six surviving chimpanzees were transferred to the Berlin Zoological Garden. For decades, historians knew little about what happened after their arrival.New research connects their fates using zoo records, correspondence and other historical evidence. The findings showed that life in Berlin was a far cry from the carefully managed research environment in Tenerife. Born in the tropical forests of Cameroon, the chimpanzee struggled to adapt to Berlin’s harsh winters. The zoo also faced severe financial difficulties after the First World War, resulting from inadequate heating and a poor starch-heavy diet of bread and potatoes instead of fresh fruit. These conditions, along with disease, pregnancy, and social turmoil within the group, are believed to have contributed to the untimely deaths of many chimpanzees.Researchers also rediscovered the preserved remains of several members of the Sultan’s clan in Berlin’s Museum für Naturkunde, where they had been unknown for decades. Modern DNA analysis of these remains may help researchers better understand the origins and genetic relationships of chimpanzees while preserving an important part of the history of chimpanzees.The study also documents how chimpanzees endured the economic difficulties of the interwar period, which further affected conditions at the Berlin Zoo. Their welfare steadily declined and, one by one, the chimpanzees who had once helped reshape psychology disappeared from the historical record. Only later did researchers begin to reconstruct their forgotten stories through archival evidence.
Why does his legacy still matter?
Researchers argue that it is as important to remember the lives of chimpanzees as it is to celebrate the scientific breakthroughs they made possible.Today, studies show that chimpanzees use tools, cooperate with each other, plan ahead, and exhibit complex social behavior. Many of these discoveries built on the foundation laid by Köhler’s pioneering work on Tenerife.However, new historical investigations remind us that scientific progress often depends on living animals whose welfare requires equal attention. By exploring the lives of the Sultan’s clan beyond the laboratory, the researchers highlight the need to acknowledge not only their role in advancing knowledge, but also the difficulties they experienced after the experiments ended.More than 100 years later, the story of Sultan, Rana, Chica, Grande, Tercera, and Tshego remains a milestone in the history of psychology and a powerful reminder of the ethical responsibilities that come with scientific research. His remarkable intelligence changed the way humans thought about the minds of other animals, while his final years were largely ignored, underscoring why compassion and animal welfare must remain at the center of modern science.