The evolution of the 'brrr factor': hominin development in cold weather
As Homo sapiens we represent the only hominin species able to survive until now. All other hominin species, including Homo erectus, the upright walking man, Homo habilis, the tool-using man and Homo neanderthalensis, the first artists of cave-painting fame, though possessing some combination of features that characterise humans today, are all extinct.
Human evolution coincided with long periods of severe environmental changes, including massive shifts in temperature. When tracing our origins in a place like Maropeng, the official visitor centre for the Cradle of Humankind Heritage site, especially on a winter morning with ice in the air, one has to wonder how humans with their rather pitiful pelts did in fact manage to survive through so many centuries of cold.
It is now widely accepted that the species Homo sapiens originated in Africa, a warm place compared to other parts of the world where other hominins lived and evolved. Some of these species may even have aided the survival of the human species by helping our ancestors to deal with the cold.
“Homo neaderthalensis was a species of hominin able to deal with the cold weather of Europe and further northern regions because of their unique anatomy,” says palaeobiologist Dr Christine Steininger, Cooper’s Cave tour leader.
Neanderthal populations in Europe endured many environmental changes, including large shifts in climate between glacial and interglacial conditions, she says.
“They managed to live in habitats that were far colder than areas where most other hominin species lived, and they were able to adjust their behaviour to fit the circumstances.”
During the cold glacial periods, they would have focused on hunting reindeer – animals that are also adapted to the cold – and during the warmer interglacial periods they would have turned to hunting red deer. When the extreme cold periods arrived, they probably shifted their range southwards toward warmer environments.
Around 46 000 years ago, Homo sapiens (humans) moved from Africa to Europe. They must have been quite unprepared for the cold and yet they survived and settled across the globe, whereas the neanderthals, who were adapted to the cold, died out and became extinct.
This is where it starts to get interesting. Direct studies of ancient DNA from neanderthal bones suggest that humans and Neanderthals interbred. Besides offering some warm bodied shelter in the storm, this may also have contributed to a more robust genetic makeup for future human generations. But still the question remains: why would one species who was, so to speak, built for the cold become extinct when another species, not really built for the cold, survive?
“Evidence suggests that adaptability to varying environments was one of the key differences between these two evolutionary paths,” says Steininger. “Many species and organisms have habitat preferences, such as particular types of vegetation (grassland versus forests). When there’s a change in the preferred habitat they can either move and try to find it elsewhere, or they can adapt to the new habitat. Otherwise, they become extinct.
“Another possibility is for the adaptability of a population – in other words, the potential to adjust to new and changing environments increases. A characteristic of humans is their ability to adjust to a variety of different habitats and environments,” says Steininger.
“Neanderthals and modern humans had different ways of dealing with environmental fluctuations and the survival challenges this posed. Homo sapiens had specialised tools to extract a variety of dietary resources. They also had broad social networks – we see this from evidence pointing to the exchange of goods over long distances. They used symbols as a means of communicating and for storing information.
"This meant that despite many climatic fluctuations, modern humans were able to expand their range over Europe and Asia, and into new areas such as Australia and the Americas. The Neanderthals, like many other species, were not as adaptable, and therefore became extinct.”
As species, humans have successfully managed to weather many a storm and blizzard through the ages. The question we need to ask now is, how well will our resilience, as the lone species of hominins, continue to succeed in the future?