Genetic and fossil records will not reveal a single point where modern humans originated, researchers have suggested.
In a new paper, experts reviewed the current understanding of how modern human ancestry around the globe can be traced into the distant past, and which ancestors it passes through during the journey back in time.
The study, published in the journal Nature, identified three key phases in human ancestry that are surrounded by major questions.
These are the worldwide expansion of modern humans about 40,000 to 60,000 years ago and the last-known contacts with archaic groups such as the Neanderthals and Denisovans, and an African origin of modern human diversity about 60,000 to 300,000 years ago.
The third phase is the complex separation of modern human ancestors from archaic human groups about 300,000 to 1 million years ago.
Co-author Chris Stringer, a researcher at the Natural History Museum, said: “Some of our ancestors will have lived in groups or populations that can be identified in the fossil record, whereas very little will be known about others.
“Over the next decade, growing recognition of our complex origins should expand the geographic focus of paleoanthropological fieldwork to regions previously considered peripheral to our evolution, such as Central and West Africa, the Indian subcontinent and Southeast Asia.”
Experts from London’s Natural History Museum and Francis Crick Institute, and the Max Planck Institute for the Science of Human History in Jena, Germany, joined together to untangle the different meanings of ancestry in the evolution of our species Homo sapiens.
They argue that no specific point in time can currently be identified when modern human ancestry was confined to a limited birthplace.
According to the researchers, the known patterns of the first appearance of anatomical or behavioural traits which are often used to define Homo sapiens fit a range of evolutionary histories.
Co-author Pontus Skoglund, from the Francis Crick Institute, said: “Contrary to what many believe, neither the genetic nor fossil record have so far revealed a defined time and place for the origin of our species.
“Such a point in time, when the majority of our ancestry was found in a small geographic region and the traits we associate with our species appeared, may not have existed.
“For now, it would be useful to move away from the idea of a single time and place of origin.”
Dr Eleanor Scerri, from the Max Planck Institute for the Science of Human History, said: “Following from this, major emerging questions concern which mechanisms drove and sustained this human patchwork, with all its diverse ancestral threads, over time and space.
“Understanding the relationship between fractured habitats and shifting human niches will undoubtedly play a key role in unravelling these questions, clarifying which demographic patterns provide a best fit with the genetic and palaeoanthropological record.”