Key Takeaways:
– The fastest land creature is the cheetah, reaching speeds of 104 km/h while the fastest airborne species are white-throated needletail swifts who fly at over 112 km/h.
– These creatures share a common trait- they are neither large nor small but intermediately sized.
– Scientists unearthed this mystery using a scalable, virtual model of the human body to explore the limits of speed depending on size.
– As per their findings, neither the smallest nor the biggest models were fastest but those around 47kg, similar to an average cheetah.
– Size impacts an animal’s speed due to a trade-off between ground force and stride frequency.
Do you know who the fastest animals on Earth are? On land, it’s the cheetah that blazes past at 104 km/h, while in water, the yellowfin tuna and wahoo reach speeds up to 75 and 77 km/h respectively. As for the sky, the white-throated needletail swift holds the record for the fastest level flight, flying over 112 km/h.
Not too Big, Not too Small
What do these record-breaking creatures share? Surprisingly, they are all middle-sized for the group of animals they represent. This fascinating correlation between size and speed sparked a puzzling question among scientists. Why do intermediately-sized animals move the fastest?
We previously thought longer legs, which come with larger size, would equate to more speed. But that theory has some big holes. Elephants, for instance, are far from being the fastest animals despite their long legs.
Uncovering the Mystery
To find answers, a team of researchers used a virtual model of the human body, called OpenSim, that mirrors all our bones, muscles, and tendons. This cutting-edge simulation has been used to understand human movement and even model the effects of surgery.
The team pushed OpenSim’s capabilities. They scaled the model down to a mouse’s size and up to an elephant’s, asking each model to run as fast as they could.
Size Matters: The Perfect Balance
Here’s where things got intriguing. The 2000 kg model couldn’t move, nor could the 1000 kg model. The largest model that could sprint was 900 kg, implying a size limit for speed. Interestingly, neither the largest nor the smallest models clinched the top speed. The most agile model weighed around 47 kg, similar to an average cheetah.
But why does size alter speed? Parsing the results, researchers found a connection between the maximum running speed and the maximum ground force a creature can generate. As animals grow bigger, their limb muscles proportionally weaken, reaching a speed limit.
Conversely, smaller creatures have stronger muscles but battle gravity which slows them down. Despite applying a stronger force to the ground, their light bodies leave the ground quickly, limiting their speed. Hence, an intermediate size offers an ideal balance between ground force and stride frequency, producing higher speeds.
Have Humans Maxed Out Their Speed?
These findings shed light on human evolution. The size of modern-day humans and their ancestors, the hominins, has varied significantly. From the 30 kg Australopithecus afarensis that lived roughly 3.5 million years ago to the roughly 80 kg Homo erectus from nearly 2 million years ago.
Given that body mass generally increased over time, it’s reasonable to say so did our running speed. Our ancestors, like the 37 kg Homo naledi and the 27 kg Homo floresiensis, probably ran slower due to their smaller size.
The average weight of modern adult humans is around 62 kg. Intriguingly, long-distance runners, typically weighing around 50 kg, come close to the ideal 47 kg weight determined by the simulation. Therefore, it seems like we’ve hit our maximum speed, barring any significant changes to our muscular structure.
All in all, it looks like nature has found the perfect size-speed equation, and whether you’re a cheetah, a swift, or a human, size does matter!