1. Potato Washing: How One Japanese Macaque on Kojima Island Started a New Behavior
The Japanese macaques on Kojima Island have been studied by Kyoto University since 1948, resulting in a family tree record spanning about 70 years [3]. According to the Kushima City guide, in 1953, a young monkey began washing potatoes in a stream, and gradually, other monkeys adopted the same action. This discovery was considered a case of "culture" because a single behavior continued to be passed to other individuals, contradicting the common belief at the time that "only humans have culture" [2]. While the name and age of the first monkey to wash potatoes appear in various explanations, they are not discussed here.
2. Why Only Some Macaques Wash Potatoes: Learning from Mothers Within Families
According to a Kyoto University public relations article, not all monkeys wash potatoes. The behavior is passed down within families, from mother to child, through observation and learning [3]. This is similar to how children might copy a friend's game at school without being taught it directly. However, monkeys do not use words to teach each other like humans do. The key point is that the behavior continues because individuals learn from their peers, rather than each monkey inventing it independently. This process is one example of what is called animal "culture" [3].
3. Chimpanzees: How Behaviors Differ from One Group to Another
In 1999, a research team led by Whiten compared long-term studies of chimpanzees at seven sites in Africa, totaling 151 years of observation [4]. They found that 39 types of behaviors, including tool use, grooming, and courtship, were habitual in some groups but absent in others. The researchers stated that these differences could not be explained by variations in food types or environments [4]. It is important to note that the 39 behaviors are the number found when comparing these seven specific sites, not the total number for all chimpanzees. The study focused on the "combination" of behaviors. The fact that each group had a different combination of habits resembled features of human culture, which had not been verified in other animals before [4].
4. Dolphin Sponge Tools: How Shark Bay Dolphins Pass Them from Mother to Daughter
In Shark Bay, Western Australia, some bottlenose dolphins use sponges as tools while foraging for food. The study paper considered this the first example of "material culture" in marine mammals, as it could not be explained by genetics or environment alone [5]. Researchers examined mitochondrial DNA, which is passed from mother to offspring, and found that this behavior was transmitted almost exclusively through one maternal line, from mother to daughter. However, the paper was cautious, using phrases like "appears to be a tool," and noted that not every instance was strictly mother-to-daughter [5].
5. Humpback Whale Lobtail Feeding: How It Spread Through the Population Over 27 Years
Humpback whales practice "lobtail feeding," where they slap the water surface with their tails to herd fish. This method was first confirmed in a single individual in 1980 and then spread through the group over 27 years [6]. By 2007, approximately 40% of this population was observed using this technique. These records were collected by observers on whale-watching boats in the Gulf of Maine [7]. The 40% figure represents the proportion "seen" doing it, so the actual rate might be higher. The first observation of this fishing method in 1980 occurred after the main food source, herring, had decreased. Thus, a new method appeared after the decline of herring [7].
6. Great Tit Experiment: How Two Trained Birds Taught a New Food Method to Others
In an experiment with wild great tits, researchers taught two birds a new way to get food. The new method spread through the birds' social connections, reaching an average of about 75% of the population [8]. Birds that were exposed to both the old and new methods tended to choose the majority method in their new group. Researchers interpret this "conformity to the majority" as a factor that supports the persistence and retention of behaviors [8]. Please read the 75% figure as an approximate number.
7. The "Hundredth Monkey" Story: Where It Differs from the Actual Records
The "Hundredth Monkey" story claims that the moment the 100th monkey learned to wash potatoes, the behavior instantly spread to the entire group. According to an explanation site, this story was admitted by author Lyall Watson to be partially improvised fiction based on fragments of personal anecdotes and legends in his book *Lifetide*. Dr. Masao Kawai, who studied Kojima Island, reportedly answered "no" when asked if the original anecdote existed [9]. The same source states that in actual Kojima Island records, the proportion of monkeys that learned potato washing was 56.6% in March 1958 and 73.4% in the summer of 1962. There is no record of the behavior spreading overnight [9].
8. Investigate It Yourself: Try Spreading a Behavior in Your Own Group
You might try or research the following things. Try to teach a family member one origami fold by showing them, without using words. Note how far it spreads and where it stops. Read the Kyoto University article and the Kushima City guide side by side, and summarize in your own words what about the Kojima monkeys was called "culture" [3][2]. If you see the "Hundredth Monkey" story elsewhere, look for its source to see what it was based on.