Lucy, the fossil hominin who lived around 3.2 million years ago, would have been no match for modern humans in a running race.
Even an average member of our species would have left her for dead in a 100-metre sprint, and the current world record holder for this distance, Usain Bolt, would have beaten Lucy by somewhere between 50 and 80 metres.
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at the University of Liverpool in the UK and his colleagues have, for the first time, attempted to determine how fast Lucy鈥檚 species, Australopithecus afarensis, could run.
The skeletal and muscular anatomy of Homo sapiens make us superb and economical runners over almost any distance, says Bates, but it is unclear when these adaptations emerged in our evolutionary history.
Lucy鈥檚 fossil remains were found in 1974 in Ethiopia and around 40 per cent of her skeleton was recovered. She was just 1 metre tall, with her weight estimated at 22 kilograms.
Her skeleton indicates that she walked on two legs, but also spent聽a significant portion of her time climbing trees. None of her soft tissues like her muscles and tendons were preserved, hindering our understanding of her athletic abilities.
Bates and his colleagues made a 3D digital model of the skeleton of A. afarensis based on Lucy鈥檚 skeleton and used a range of data from living mammals, particularly great apes, to reconstruct important missing aspects of her anatomy, such as the size and properties of her leg muscles.
鈥淲e essentially reconstructed a simplified digital 鈥榬obot鈥� of A. afarensis, made up all major skeletal and muscular features that determine running speed,鈥� says Bates. 鈥淲hat we then needed to do was find a way to objectively make the digital model move in a given way, in this case to run as fast and economically as it can.鈥�
To do this, the researchers experimented with millions of different combinations of ways to activate the leg muscles until the computer program found the combination that resulted in the fastest and most efficient running gait. To ensure their model was as accurate as possible, they also analysed the running performance of a non-elite human athlete, whose top speed was around 8 metres per second.
After modelling a range of different kinds of muscle anatomy on the 3D hominin, from ape-like calf muscles through to human-like ones, the top speed of A. afarensis ranged between 1.74 m/s through to 4.97 m/s.
鈥�Australopithecus was still much slower than the human in relative terms, even after correction for differences in body size,鈥� says Bates.
Even if Lucy had had muscles adapted for running like ours, such as ankle muscles with short fibres and a long Achilles tendon, then she still couldn鈥檛 have run as fast in absolute or size-corrected mechanical terms as a modern human.
鈥淭his tells us that the body shape of A. afarensis is significantly limiting its running speed compared to that of modern humans,鈥� says Bates.
鈥淩unning speed itself is ecologically important because it鈥檚 one important determinant of ecological success, for example in an animal鈥檚 ability to outrun predators and capture its own prey.鈥�
at the Australian Museum in Sydney says the human capacity to run has been fundamental to our success. While lots of animals are faster than us over short distances, 鈥渙ver a long distance, we can outrun anything on the planet,鈥� she says. This ability to run allowed us to extend our range around the globe and hunt in groups.
The research shows that just because an ancient hominin could walk, it doesn鈥檛 mean it could run well, says Way. 鈥淚t means there鈥檚 a separate evolutionary path to walking to be able to run as well as a modern human,鈥� she says. 鈥淗ominins had to evolve separate traits.鈥�
at the City University of New York says the finding that A. afarensis wasn鈥檛 a specialised runner has all sorts of implications. 鈥淪ome researchers have argued that Lucy was just like humans in terms of her bipedal capabilities, but this research suggests that is not so and that her species was not as well adapted to running as we are,鈥� he says. 鈥淭he study strongly supports the theory that, within the genus Homo, there was strong selection for running behaviours.鈥�
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