900,000 years ago humans risked extinction, according to a study published in ‘Science’, a collaboration between two Chinese scientists from the Chinese Academy of Sciences, Yi-Hsuan Pan and Haipeng Li, and two Italian palaeoanthropologists, Giorgio Manzi of Sapienza in Rome and Fabio Di Vincenzo of the Natural History Museum of the University of Florence.
The study took the genomes of 3,154 people alive today, belonging to 50 different populations, 10 African and 40 non-African. The scientists analysed their genomes and, knowing how often significant variations occur that lead to differentiation between groups, and using a statistical model, they were able to work out how many of us there were on the planet 900,000 years ago.
The discovery was astonishing: 930,000 years ago only 1,280 fertile individuals remained, fewer than the pandas alive today, which are at risk of extinction.
Before then the population numbered about 100,000 individuals, so it fell by roughly 99%. But what caused this huge decimation? It seems that, in this case too, climate change is to blame. There was an alternation of glacial and interglacial periods, while Africa was marked by extreme aridity. Conditions were therefore not favourable to the development of the human species. The scientists admit, however, that the explanation is little more than a hypothesis, and the causes remain to be clarified.
