Shift
When humans migrated from Africa to other parts of the globe, they carried with them a certain set of genes. Over the many thousands of years that have passed since, a good deal of these genes have been subjected to minor or perhaps major changes as our ancestors adapted - by the grace of natural selection - to their new environments. One such gene is ACTN3 that produces a protein known as α-actinin-3, itself an integral part of muscle. About 20 years ago, researchers discovered, quite by chance, that many humans - an estimated 1.5 billion today! - have no α-actinin-3 at all in their muscle. Yet they are perfectly healthy individuals. The researchers also observed that humans who had no α-actinin-3 had greater endurance, while those who did sport the protein were usually good sprinters. The absence or presence of α-actinin-3 in muscle depends on a specific mutation whose effect can actually change the nature of muscle fibre. This may have been a consequence of adapting to colder climates, but the side effects are fortunate for athletes: either they have the ability to run far effortlessly or the skill to run a short distance fast.
