How do humans compare against other animals?
Many animals are capable of short-distance sprints, but few do endurance running, besides horses, wolves and ostriches. None of the other primates run long distances and humans are very unusual in that we can run for very long distances at a sustained pace – if you’re in reasonable physical condition.
When did our ancestors gain running ability?
Based primarily on the structure of bones and likely implantation of muscles, the fossil record says it probably began with Homo erectus, which eventually gave rise to our lineage. About 2 million years ago, the skeleton changed dramatically: you got a structure that’s much like modern humans – the striding, bipedal gait of a healthy young person, which can break into a run
Which genes influence endurance running?
CMAH is the first known gene that might contribute to endurance running – it’s been around for 500 million years and got lost in our ancestors. The gene produces an enzyme that adds an additional oxygen atom to molecules on the cell surface, called sialic acid. Throughout the body, sialic acid enables cells to interact with one another.
We still have the same amount of total sialic acid, but we lost one major form due to a mutation in the CMAH gene about 2-3 million years ago – which coincides with when our ancestors gained the ability to run long distances.
You made mice with human-like mutated genes. How did they run?
There were two tests. One was a stress test: we put normal and mutant mice on treadmills and they ran until they reached exhaustion. The regular mice ran for 25 minutes, whereas the mice with human-like CMAH genes ran for 35 minutes. Importantly those mice had not even been trained, they had been couch potatoes. Then we put running wheels into the cages; mice love to run – they run kilometres at night.
Initially there was not much difference, but over 10-15 days, the ‘humanised’ mice got better. And when we took those trained mice and put them back on the treadmill test, the difference was even more obvious: the mutant mice ran for 60 minutes instead of 40, so around 50 per cent longer. We collaborated with Ellen Breen, who looked at their muscle biologically and showed it had decreased fatigue, improved oxygen utilisation and some other factors.
What does your study reveal about humans?
Of course, mice don’t have many other features that humans have, such as our upright posture and ability to sweat. But if we can understand the difference between the two kinds of mice in more physiological-, molecular-level detail, that may be relevant to athletic training. Evolution gave humans this benefit of being able to do sustained exercise. It’s clearly part of our genetic heritage. The irony is that this CMAH gene mutation may have made us more prone to certain diseases, such as diabetes and cardiovascular disease.
But if you just did your exercise regularly, especially endurance exercise, you would benefit.
This is an extract from issue 328 of BBC Focus magazine.
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