The Vulnerable Ape theory of human origins.

PhysOrg turns the “brutal caveman” stereotype on its head, with a new look at our earliest ancestors as sensitive folks who got a leg up on the competition because we were 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.

Dr Nick Winder, from the School of Arts and Cultures, Newcastle University, explains: “This is a new way of thinking about ‘fitness’. It wasn’t just a matter of having good genes yourself because half your offspring’s genes come from someone else. The pool of potential mates would be small and individuals would have to accept the genes on offer or fail to reproduce at all. On some occasions there would be matings between close kin, on others, there would be matings across species boundaries.

“In situations where the probability of producing disabled offspring was high, the ‘fittest’ individuals would be those that could help their offspring co-exist with this vulnerability. Those that were a little smarter, more flexible, and more compassionate would have been at an advantage.”

The researchers suggest that human and non-human primate lineages may have diverged and re-converged many times, and that the conventional ‘inverted tree’ model of evolution should be replaced with a network of diverging and re-crossing gene-streams.

…”Matings across species boundaries” is such a polite way to put it.