The Broken Hill skull, discovered in 1921 by miners in Zambia, is one of the best-preserved fossils of the early human species Homo heidelbergensis, who roamed Southern Africa. The fossil is estimated to be about 300,000 years old, according to Australia’s Griffith University scientists, who led an international team to date the skull of an early human found in Africa, potentially upending human evolution knowledge with their discovery.
The research also suggests that human evolution in Africa around 300,000 years ago was a much more complex process, with the co-existence of different human lineages. “Previously, the Broken Hill skull was viewed as part of a gradual and widespread evolutionary sequence in Africa from archaic humans to modern humans,” said Chris Stringer, curator at the Natural History Museum in London. ” But now it looks like the primitive species Homo naledi survived in southern Africa, H. heidelbergensis was in Central Africa, and early forms of our species existed in regions like Morocco and Ethiopia.”
“We can now identify at least three distinct and contemporary [Homo] lineages in Africa about 300,000 years ago, but we don’t yet know whether our ancestry was largely or entirely contained within the H. sapiens part of that variation,” says paleoanthropologist and study coauthor Stringer.
Underscoring the complexity of human evolution, in 2017, geologists demonstrated that another hominid species, Homo naledi, existed in southern Africa between 236,000 and 335,000 years ago. This was potentially the same time that modern humans first emerged in Africa, which created is a puzzle to scientists, who long held that there was only one species in Africa at this late time period – Homo sapiens. How did this species exist alongside others with brains three times its size?
The discovery of Homo naledi by Professor Lee Berger of Wits University and his team at the Rising Star caves in the Cradle of Human Kind in 2013 was one of the largest hominin discoveries ever made and hailed as one of the most significant hominid discoveries of the 21st Century.
“Naledi’s brain seems like one you might predict for Homo habilis, two million years ago. But habilis didn’t have such a tiny brain–naledi did,” said anthropologist John Hawks. Big brains were costly to human ancestors, and some species may have paid the costs with richer diets, hunting and gathering, and longer childhoods. But that scenario doesn’t seem to work well for Homo naledi, which had hands well-suited for toolmaking, long legs, humanlike feet, and teeth suggesting a high-quality diet.
Professor Rainer Grün from the Environmental Futures Research Institute led the team which analysed the Broken Hill (Kabwe 1) skull and other fossil human remains found in the vicinity including a tibia and femur midshaft fragment. The material is curated at the Natural History Museum in London. The remains have been difficult to date due to their haphazard recovery and the site being completely destroyed by quarrying.
Using radiometric dating methods, Grün’s analyses now puts the skull at a relatively young date, estimating it is between 274,000 and 324,000 years old. Publishing their findings and methodology in Nature, Grün said “the new best age estimate of the fossil impacts our understanding of the tempo and mode of modern human origins.”
Grün said his team’s research adds to new and emerging studies which question the mode of modern human evolution in Africa and whether Homo heidelbergensis is a direct ancestor of our species.
The Daily Galaxy, Andy Johnson, via Griffith University
Image credit: Natural History Museum in London