New study suggests that the ability to adapt behaviourally, rather than biologically, was likely key to our evolutionary success and to how we came to be the last surviving human species.
A new study published today in Nature Scientific Reports suggests that the ability to adapt behaviourally, rather than biologically, was likely key to our evolutionary success and to how we came to be the last surviving human species.
Colonisation of new habitats and global expansion is a key characteristic of humans, differentiating us from our ancestors and nearest relatives. It is important therefore, to understand how we adapt to new environments and how human adaptation differs from that of our nearest living relatives, non-human primates.
Climate is a key source of environmental stresses when any species expands its habitat and research shows that mammals vary in size and shape in predictable ways depending on the climate they live in.
Humans living in different climates fit these general patterns, however, it has previously remained unclear whether the same climatic stresses lead to similar skeletal adaptation in humans as in other primates.
Lead author Dr Laura Buck of the PAVE research group, Department of Archaeology, University of Cambridge said, “We wanted to see if humans are special in the way they adapt to environmental stresses, such as climate. This might tell us something about why we are such a unique and successful species and the only type of human still living. It has been suggested that humans are unique in primarily relying on cultural adaptation such as shelter, clothes and fire, reducing their need for biological adaptation. If human skeletons show less climatic adaptation than other primates, it would suggest that behavioural adaptation is of greater relative importance than biological adaptation among humans.”
The study compared differences in skull shape between ancient humans from different climates across Japan to differences between those monkeys living in the same habitats to see if each species varies in similar ways.
Northern Japanese macaque
Photo credit: Yblieb, Attribution 4.0 International (CC BY 4.0)
Japan offers an excellent environment for such research due to the variation in climate in a relatively small area and because the habitats of the ancient humans and living monkeys overlap. Japanese macaques, which are unusual in living in both cold and warm climates (most monkeys live in the tropics), make a useful comparison for this type of study.
What were the results?
Dr Buck continues, “We found different patterns of adaptation in the two species. Monkeys living in cold areas had clearly different shaped skulls to those from warm areas. The skulls of monkeys living in cold, dry, more variable climates show shapes similar to those of other animals which have undergone adaptation to the cold, suggesting this is also the case for the monkeys. Within the humans the differences between different groups and individuals was not patterned by climate, suggesting that they had not undergone adaptation to cold or heat.”
“One major difference between how humans and other primates adapt is that humans have a greater range of behavioural adaptations, including things like fire, shelter and clothes. We suggest that these behavioural differences protected the humans from climatic stress, which meant that they didn’t have to adapt biologically by altering their skeletons.”
“Behavioural adaptation is often more flexible and less energetically costly than biological adaptation. It is also easy to share between individuals and groups. The same person can readily adapt to many different environments using different behaviour and technology.”
Why does it matter and how are the results relevant to climate change today?
Dr Buck concludes, “Uncovering the differences between humans and other primates can tell us about what makes us human and what might lie behind our evolutionary success. We are the only primate species to inhabit such a wide range of habitats across the globe and the sole remaining human species alive today, this may be related to our ability to adapt rapidly to almost any environment using our complex cognition and behaviour.”
“In some ways these results might offer us hope, as they highlight the creativity and flexibility of humans faced with new environmental challenges. On the other hand, it is by using this same behaviour that we have changed our environments in a way fundamentally different to other animals and brought about this human-made climate change catastrophe which we may be unable to mitigate.”
"Evidence of different climatic adaptation strategies in humans and non-human primates" L. T. Buck, I. De Groote, Y. Hamada, B. R. Hassett, T. Ito & J. T . Stock. 2019. Scientific Reports https://www.nature.com/articles/s41598-019-47202-8
