What If? The Evolutionary Basis for Different Pathways

All too often, we see our evolutionary past as some inevitable ladder of progression. In considering our emotional connections, it is easy to imagine that the increased external friendliness and sensitivity seen in ‘modern’ humans represents some progressive or superior development from a more aggressive past. However, a close consideration of how external friendliness changes in closely related species reveals a far more complex picture, with advantages and disadvantages to different evolutionary pathways, each displaying a different type of prosocial or collaborative behaviour.

There are always many possible evolutionary pathways, affecting brains, bodies and behaviours. Here, however, we focus on simple contrasts in the adaptive routes followed within our nearest living relatives, chimpanzees and bonobos, and those within our closest friends, wolves and dogs. This brings some insights into how an increased openness, and the capacities to develop new external bonds, may have evolved. We reveal that each evolutionary pathway brought both advantages and disadvantages, depending on context, rather than any specific pathway being a progression. Our similar physiological and behavioural adaptations under pressures to be more tolerant (discussed in Part 2) suggest that the same processes that occurred in these species also affected humans. An understanding of our evolutionary past as one of different alternative trajectories, and of possibilities and constraints along these, helps to frame our understanding of the process of human evolution, and the story of our origins.