6 How do atoms absorb & emit light? â¢ Key idea: Energy â¢ A photon carries energyâ¢ Electron in orbit has energy because it is moving and it is pulled by nucleus. â¢ When atom absorbs photon, energy of photon promotes electron to higher energy.
Until now, researchers believed that homo sapiens, the direct descendants of modern man, evolved in Africa about 200,000 years ago and gradually migrated north, through the Middle East, to Europe and Asia.
Who were the first humans? Scientists agree that our early ancestors, Homo erectus, first appeared in Africa 1â2 million years ago. They spread throughout the world and evolved into ancient humans. Most believe that modern humans evolved in Africa, and gradually replaced all the other ancient humans (the 'Out-of-Africa' theory). Some scientists believe that ancient humans may have evolved into modern humans all over the world at around the same time (the 'multiregional' theory). Either way, by about 30,000 years ago, we â Homo sapiens â were the only humans left on the planet.