Human evolution

The road to humanity was a long one, and we are still exploring its byways. It began in Africa some 7 million years ago when our lineage split from that of our closest living relatives the chimpanzees. Our ancestors still resembled apes nearly 4 millions years later. This includes Lucy, a 3.2-million-year-old human ancestor discovered in Ethiopia, from a group called the australopiths. In some ways Lucy was very ape-like: she had a chimp-sized brain and long arms that suggest she spent a lot of time in trees. But she also walked on two legs, like modern humans.

Hominins living at this time probably made simple stone tools, but our ancestors didn’t really begin to look and behave like us until about 1.9 million years ago with the appearance of the genus Homo. Homo erectus fossils have been found in Europe and Asia, marking it out as the first hominin to make its way out of Africa. It produced far more sophisticated tools than its predecessors, and was probably also the first hominin to control fire. Some researchers believe it invented cooking, providing them with more energy to allow bigger brains to evolve.

However, the anatomy of Homo erectus suggests it was incapable of speech. That talent most likely came with Homo heidelbergensis, which evolved from Homo erectus in Africa about 600,000 years ago. Populations of Homo heidelbergensis living in Eurasia are thought to have given rise to the Neanderthals in the west and an enigmatic group called the Denisovans in the east. And was it was considered to be our direct ancestor too. However, new evidence is completely rewriting this part of the human story.

Until recently, the out-of-Africa paradigm had Homo sapiens evolving in East Africa around 150,000 years ago, becoming capable of modern behaviours around 60,000 years ago, and then migrating en masse to colonise the entire world. But new analyses of fossils, tools and DNA tell a different story. It looks like our species is far older – at least 300,000 years old – and was behaviourally sophisticated from the start. We did evolve in Africa but, rather than originating in one region, we emerged from populations across the continent in a process called “African multiregionalism”. Everything, from the identity of our last ancestor, when our species left Africa and what happened next, is up for revision. These are interesting times to be exploring the human story – no doubt, there will be more plot twists to come.