An elephant never forgetting

Within a clan of elephants all members are known to one another and, since a clan will usually have at least 100 adult members, and may have twice that, this means an adult can recognise and have meaningful social relations with that many other individuals. A figure of between 100 and 200 acquaintances is similar to the number of people with whom a human being can maintain a meaningful social relationship—a value known as Dunbar’s number. To deal with so many peers, and remembering details of such large ranges may require big hippocampuses. These structures, one in each cerebral hemisphere, are involved in the formation of long-term memories. Compared with the size of its brain, an elephant’s hippocampuses are about 40% larger than those of a human being, suggesting that the old proverb about an elephant never forgetting may have a grain of truth in it. The Economists June 2017