Ancient Diseases of Human Ancestors

I’ve written before about ancient diseases of the ice age , but this time I’m going even further back in time, to diseases that were present in the first human-like hominids. Although many human infections only developed after human settlements and animal domistication, early human ancestors would still have been fighting off bacteria and other nasty diseases. Some of these diseases are still around today.

So how do you start exploring the age of bacteria, and trying to discover when they developed as a human-infecting species? One way to look for the age and relatedness of strains is by looking at the bacterial DNA and examining the rate of mutations that cause very small differences between bacterial strains (single nucleotide polymorphism – shown in the image below) . It is also possible to identify “pseudogenes” within the bacteria – little bits of viral DNA or bacterial genes that became redundant due to a change in the bacterial lifestyle (for example genes for extracellular lifestyle that started decaying and mutating once the bacteria became fully intracellular). These can be dated using the ‘molecular clock’ – which assumes a steady rate of background mutation and can provide approximations of the age of genes.
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