Discovering Our Ancestors
Fossil find suggests Homo erectus emerged 200,000 years earlier than thought.
The human evolutionary path is complicated. It’s almost impossible to say exactly when we modern humans became “us”. This quandary is best articulated by the famous naturalist Charles Darwin in his book The Descent of Man:
“In a series of forms graduating insensibly from some apelike creature to man as he now exists, it would be impossible to fix on any definite point where the term ‘man’ ought to be used.”
understanding of modern humans’ own genus, Homo, has
taken many turns over the last century. Homo erectus, one of
our purported ancestors, was first discovered in Indonesia in 1891 by geologist
and anatomist Eugene Dubois. Since then, representatives of both this
species, and other Homo, have been found
across the world; for instance, in 2015, a new species of Homo, Homo naledi, was
discovered in South Africa. Another new Homo species, Homo luzonensis, was found more recently in the
Philippines in 2019.
discoveries, combined, have led scientists to set Homo erectus‘ emergence at about 1.8 million years ago,
with the oldest known record coming from Dmanisi, Georgia and an
important slightly later record from the East African Rift valley. But
our new discovery in South Africa’s Cradle of Humankind, which has just
been published in Science, suggests that Homo erectus actually
emerged 200 000 years earlier than we thought. We were part of a team from
South Africa, Australia, Italy and the US that discovered a Homo erectus cranium which has since been dated to
almost 2 million years ago.
is a hugely important find. It reasserts that Homo erectus’ origins
are in Africa, not Asia. Our discovery suggests, though, that Homo erectus likely did not evolve in eastern Africa
as so often thought but perhaps somewhere else in Africa, or potentially in
South Africa itself. More evidence is needed before firm conclusions can be
reached, of course. But the South African find means that the Drimolen
fossil site, where we made the discovery, could represent an important shift in
the simple narrative that all early species of human ancestry are East African.
Drimolen Fossil Hominin site in the Cradle of Humankind, northwest of
Johannesburg, has been excavated since its discovery in 1992. The site is best
known for its Paranthropus robustus, another ancient hominin species with
massive teeth, as well as some early Homo fossils. The most famous specimen
from Drimolen is the most complete skull of Paranthropus robustus ever
discovered, DNH 7. It was here that members of our team found the fossil
cranium that has been named DNH 134. Its nickname is Simon, named for the site
technician whose contribution to the team was immeasurable. Simon Mokobane
sadly passed away in 2018, but his expertise, unwavering support and fossil
knowledge will forever be remembered.
2015, during the Drimolen Field School, a student named Richard Curtis began
excavating an intriguing, but highly fragmented specimen. At first, no one was
sure what it was from but in-field reconstructions quickly revealed that it was
a hominin cranium. We used a battery of dating methods, including Uranium-lead
dating on the flowstones, Uranium-Series Electron Spin Resonance on fossil teeth
and Palaeomagnetism on sediments. Each of these complimentary techniques helped
to establish a very narrow age of 2.04-1.95 million years for the whole
Drimolen Main Quarry and the fossils found in it, including DNH 134.
134 is extremely significant. Its discovery and dating mean that the story
of Homo erectus and its journey out of Africa is more
complicated than previously thought. Also, we know too that South Africa played
a seminal role in this key species that ultimately led to us.
will continue at the Drimolen site. We aim to continue excavating using a new
method where our efforts are focused along the breccia (fossilised rock with
fossils in it). This has proved fruitful with not only the discovery of DNH
134, but also a male Paranthropus robustus skull
as well as a number of other hominin remains we are still studying. The site
also has a wide variety of animal fossils from both extinct and living species,
all of whom add to the overall story that we aim to build about how our ancient
will also continue to encourage young palaeoanthropologists from across the
African continent to get involved in excavations. The site hosts an annual
field school with international partner institutes and offers full
scholarships exclusively to students from African countries, with South
Africans having first preference. The idea behind this is to ensure that
researchers from the continent and country are at the forefront of future
discoveries that add to the human story.
Source: The Conversation. Authors:
Stephanie Baker, Angeline Leece, Jesse Martin, Matthew
Caruana, Prof. Andy Herries, Renaud Joannes-Boyau