The early humanoid ancestor Homo erectus was the first to be able to run long distances despite having a ‘wide and deep chest’ like Neanderthals, a new study reveals.
Researchers at the Natural History Museum in London examined the ribcage of the famous Homo erectus skeleton – Turkana Boy – to better understand the species’ breathing.
This is the first time that the details of the rib cage have been studied and revealed in detail by scientists, and it bears no resemblance to what they predicted based on their legs and arms.
The homo erectus had a more robust build than its reputation as a long-distance runner would suggest, but that doesn’t mean they weren’t good runners, the team said.
Fred Spoor, lead author of the Natural History Museum study, said Homo erectus would have been “more a rugby player than a slim athlete.”
Researchers from the Natural History Museum examined the rib cage of the famous Homo erectus Turkana Boy skeleton (right) to better understand the species’ breathing. The photo on the left is an artistic reconstruction of Homo erectus
Experts previously thought that ancient hominin species must have had a much slimmer body to allow them to run long distances, but this turned out to be untrue.
Fred Spoor of the Natural History Museum and the study’s lead author said this has implications for our understanding of human evolution.
“It appears that the completely modern human body shape evolved more recently than previously thought, rather than as early as two million years ago when Homo erectus appeared,” explained Professor Spoor.
The evolution of the modern form of the human body is important to understand how we and our ancestors adapt to our natural environment.
As modern humans, Homo sapiens, we have a relatively tall and slim body shape that contrasts, for example, with the shorter, more robust, and heavy-bodied Neanderthals.
The ribcages of modern humans (left), Turkana Boy (center), and Neanderthal (right), shown in front view (top row) and left side view (bottom row) Individual fossils of ribs and vertebrae of the Turkana boy ( KNM-WT 15000) that were used to rebuild your rib cage using virtual computing techniques
Scientists have long assumed that our body shape originated with the first representatives of Homo erectus, but that may not be the case.
Homo erectus first emerged in the context of climate change and receding forests in tropical Africa, more than two million years ago.
Our tall, slim bodies seem evolutionarily advantageous in the expanding hot and dry savanna, helping to avoid overheating and well suited to running bipeds over long distances on more open terrain.
The fossils attributed to Homo erectus, examined before the chest study, seemed to point to longer legs and shorter arms than our previous ancestors would have been good at running long distances.
This contrasts with Australopiths, which were bipeds when they were on the ground, but still retained some commitments to tree life.
Several modern body features are particularly clear in the 1.5 million-year-old fossil remains of a Homo erectus adolescent found west of Lake Turkana, Kenya.
Known as the Turkana Boy, it is the most complete skeleton of a fossil human ancestor ever found.
Studies of how this individual walked and ran have been largely limited to his legs and pelvis rather than his rib cage.
However, for the endurance run, his breathing abilities would also have been relevant, according to the team at the London Museum of Natural History.
The problem is that getting an idea of the chest and the movement of the breath from a ‘mixture of ribs and vertebrae fossils’ is difficult with conventional methods.
This led the team behind this new discovery to turn to technology: thanks to modern imaging and reconstruction techniques they were able to study his rib cage and how he would have breathed in more detail than was previously possible.
A Turkana child’s three-dimensional virtual rib cage could be reconstructed, and its adult form could be predicted if this adolescent had fully grown.
The shape of the rib cage was compared to that of modern humans and a Neanderthal, and virtual animation allowed us to investigate the movement of the breath.
“The results are now changing our understanding of Homo erectus,” says lead author Markus Bastir, adding that his chest was wider than that of most modern humans.
Daniel García Martínez said that the rib cage of Homo erectus seemed more similar to that of more robust human relatives, such as Neanderthals, than modern humans.
Individual Turkana rib and vertebra fossils (KNM-WT 15000) that were used to rebuild his rib cage using virtual computer techniques
In fact, he said that species like Neanderthals would have inherited that robust form from the chest of Homo erectus earlier.
“The shape of our own body with its flat, high chest and narrow pelvis and rib cage probably appeared recently in human evolution, with our species, Homo sapiens,” says Dr. Scott Williams, co-author of the study at the New York University.
So instead of inheriting tall, flat chests, a narrower pelvis, and a narrow rib cage from Homo erectus, we were the first to develop those traits.
The document speculates that these changes in the shape of our bodies may have optimized breathing capabilities for long-distance running and other endurance activities.
Make modern humans the first true long-distance runner.
“Homo erectus was perhaps not the lean, athletic long-distance runner we imagined,” Spoor said, adding that he had “higher body weight estimates than previously obtained.”
“This iconic ancestor probably looked a bit less like us than we portrayed,” he added.
The article is published in Nature Ecology and Evolution.
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