by David Garner
A new evolutionary theory explains how critically small populations of early humans survived, despite an increased chance of hereditary disabilities being passed to offspring.
Anthropologists at the University of York and Newcastle University have studied how our earliest ancestors coped during periods when the population dwindled, and have developed a model of early hominins as ‘Vulnerable Apes’.
Small numbers of individuals in the distant past would sometimes be driven to landscapes that allowed them to avoid predators and competitors, or exploit emergency resources. They would have become isolated, creating genetic ‘bottlenecks’ which brought disabling genes to the surface.
The researchers argue that these groups would have experienced a new type of selection pressure – not selection in favour of individuals with the ‘best’ genes but selection that favoured those who were able to cope with the challenges that their genes threw at them.
They speculate that our need to socialise and ability to experiment and learn new behaviours, as well as our compassion and communication skills, arose as coping strategies that allowed our ancestors to get through these bottlenecks. In so doing, they turned ‘disabilities’ such as weak jaws, hairless bodies, short, weak arms and straight feet that can’t climb trees, into opportunities that formed the platform for future human evolution.
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