Epreuve orale de DNL Sciences Session de juin Baccalauréat 2016 Durée de préparation : 20 minutes Durée de l'épreuve : 20 minutes (10 minutes de présentation orale ; 10 minutes d'entretien)

Theme : EVOLUTION

The adult skull of Homo floresiensis (centre) at the 2004 press conference announcing the species' discovery. Homo floresiensis remains of the most recently discovered early human species, Homo floresiensis (nicknamed ‘Hobbit’), have been found between 95,000 and 17,000 years ago on the Island of Flores, Indonesia. Despite their small body and brain size, H. floresiensis made and used stone tools, hunted small elephants and large rodents, coped with predators such as giant Komodo dragons, and may have used fire. Sources: http://humanorigins.si.edu/evidence/human-fossils/species/homo-floresiensis Question: Using the documents, explain evolutionary mechanisms that could have played in Flores to get “Hobbits”. Doc1: The diminutive stature and small brain of H. floresiensis may have resulted from island dwarfism—an evolutionary process that results from long-term isolation on a small island with limited food resources and a lack of predators. Pygmy elephants on Flores, now extinct, showed the same adaptation. The smallest known species of Homo and Stegodon elephant are both found on the island of Flores, Indonesia. However, some scientists are now considering the possibility that the ancestors of H. floresiensis may have been small when they first reached Flores. Doc2 :

Sources: http://www.nature.com/news/human-evolution-small-remains-still-pose-big-problems-1.16170