“Multiple lines of evidence suggest that the ancestors of most humans living outside Africa left the continent in one migration 60,000 years ago. But there is some evidence that pioneer modern humans (Homo sapiens) made forays outside Africa before this time.
In January, scientists unveiled the jawbone of a modern human who died in Israel 185,000 years ago, tens of thousands of years earlier than previous evidence. Received wisdom suggests that these earlier excursions failed to provide modern humans with a permanent foothold in Eurasia.
But the jawbone fits in with the emerging picture of earlier out-of-Africa migrations that spread further into Eurasia than many had believed. These pioneers appear to have lived alongside other human species such as the Neanderthals and Denisovans. But it remains a mystery as to why their genetic signatures are not preserved in people alive today.
The field of ancient DNA - which involves extracting and analysing genetic material from long-dead people - has provided us with unprecedented insights into the past. One striking result from 2018 was the discovery that the ancient people of Britain were almost completely replaced in a mass migration from the continent about 4,500 years ago.
The Neolithic Britons had just erected the big stones at Stonehenge when they were overrun by newcomers known as the Beaker people. This resulted in 90% of the British gene pool being replaced in just a few hundred years. Why this happened is unknown. But disease, famine and conflict are all potential candidates.
In a different study released in 2018, researchers showed that 50,000-year-old bone fragments from Russia belonged to girl who was half Denisovan and half Neanderthal. The Denisovans and Neanderthals were distinct species of human who inhabited Eurasia before our species - Homo sapiens - left Africa.”