Three Different Human-like Species Lived Concurrently in Ancient Africa
The oldest known Homo erectus and Paranthropus robustus fossils have been found in a hilltop cave and a new study details a critical period of hominin evolution showing that two million years ago “three different human-like species lived side-by-side in South Africa”.
The new research, published in the journal Science by Andy Herries and colleagues from La Trobe University in Melbourne, Australia, expands on the traditional idea that a single human species dominated the globe. The new evidence comes from bones discovered at the Drimolen Cave Complex near Johannesburg which are thought to be the earliest known remains of H. erectus, a direct ancestor of modern humans ( Homo sapiens).
The Drimolen Cave Complex has produced multiple ancient fossils over the decades and the three groups of hominins are represented: Australopithecus (including the famous “Lucy” fossil from Ethiopia), Paranthropus (the robust australopithecines), and H. erectus (modern human ancestor). The remains were analyzed with electron spin resonance, which detects and quantifies unpaired or odd electrons in atomic or molecular systems: palaeomagnetism, studying the earth's magnetic field in rocks, and uranium-lead dating, used to date rocks that formed and crystallized between 1 million and 4.5 billion years ago.
The location of the Drimolen Cave Complex. (Herries / Science)
Tracking The First Waves of Human Species Out Of Africa
H. erectus is thought to be the earliest human species to have migrated out of Africa, and a few years ago two skull caps, one from P. robustus and the other from H. erectus, were discovered in the Drimolen Cave Complex. The later represents the oldest bone fragment of the ancient species that has been found anywhere in the world.
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P. robustus skullcap: the species was a primitive relative of human species. (Herries / Science)
Co-author of the study, Stephanie Baker, from the University of Johannesburg told Science Mag that the team had collated all of the dates provided by the three dating techniques which showed the fossils found at Drimolen date from “2.04 to 1.95 million years ago”.
Baker said until this find scientists had always assumed H. erectus, one of our direct ancestors, originated from eastern Africa but the skull cap, named DNH 134, shows H. erectus possibly came from southern Africa and later moved northwards into East Africa from where “they went through North Africa to populate the rest of the world”.
The human species, DNH 134 H. erectus neurocranium. (Herries / Science)
Mapping Nonlinear Distribution Patterns of Human Species
What this all means is: early humans did not migrate out of Africa in a linear fashion, an idea that was highlighted in another study published this week in the journal Nature which provided dating on a skull found in a quarry at Kabwe, Zambia, in 1921, ‘the Broken Hill skull’. More advanced than H. erectus but more primitive than those of modern humans, this skull was first considered to be around 500,000 years old. Lead author of the new study, Professor Chris Stringer, from the Natural History Museum in London, UK, said it is considered by many researchers to belong to a species called Homo heidelbergensis - a common ancestor of modern humans and Neanderthals.
However, other scientists who have dated samples of bone and teeth from this skull have shown that it is much younger - between 324,000 and 276,000 years old, and it would be expected to show intermediate features between H. heidelbergensis and H. sapiens, but it shows “no significant features of our species”, said Dr. Stringer, who thinks it implies that “at least three different Homo species co-existed at this time in Africa”.
Realigning Theories About Human Origins
Professor Stringer said in the new paper that the Broken Hill skull had been previously viewed as part of “a gradual and widespread evolutionary sequence in Africa from archaic humans to modern humans”. But now it looks as if the primitive species Homo naledi survived in southern Africa while H. heidelbergensis was in south-central Africa, and that early forms of our species existed in Morocco and Ethiopia.
The Broken Hill skull from Zambia is younger than scientists previously suspected. (Natural History Museum in London)
Professor Stringer also points towards another Science paper analyzing proteins from 1.9 million year-old H. erectus and Homo antecessor fossils found at Dmanisi in Georgia, thought to have been present in Spain from 1.2 million years ago to 800,000 years ago. This protein analysis helped determine relationships between the two species and the study showed that H. antecessor, “whose validity as a separate species has been questioned in the past”, is a close sister lineage to modern humans and other recent Homo species, such as Neanderthals and Denisovans.
According to a report in National Geographic, coauthor Jesse Martin said “An Asian origin for H. erectus now seems exceedingly unlikely,” because the earliest evidence for H. erectus is now from South Africa, and what’s more, there is no candidate ancestor for H. erectus in Asia and if you dig any deeper at sites where H. erectus remains have been found, “there are no hominins there”.
Top image: A new study finds that three different human species lived alongside each other. Source: pict rider / Adobe Stock.
By Ashley Cowie