When it was believed that humans had appeared suddenly, placed on Earth by a divine breath, separated from the rest of the animals, it was possible to study their nature by observing how they behaved in present-day societies. The situation became complicated when, in light of the evolutionary theory, we knew that we were one more branch of the tree of life, and that, although there are millions of years between us and other animals, we share ancestors. To search for the spark that gave rise to this species capable of accumulating knowledge, communicating it and transforming its environment like none before, scientists have had to go beyond academic speculation and get their hands dirty, scratching the floors of caves and ravines, in search for answers.
