Human beings are a tropical species. We’ve lived in hot climates for most of our evolutionary history, which may explain why so many of us spend the winter huddled under a blanket, clutching a hot water bottle, and dreaming of summer.
In fact, all the apes that exist live in the tropics. The oldest known fossils of the human lineage (hominids) come from central and eastern africa. Hominids that spread northward to higher latitudes faced for the first time frigid temperatures, shorter days that shortened the time to forage, snow making hunting difficult Y an icy wind that worsened the loss of body heat.
Considering our limited adaptation to cold, how is it that our species has come to dominate not only the ancestral warm lands, but all regions of the planet? The answer lies in our ability to develop complex cultural solutions to life’s challenges.
The first indications of the presence of hominids in northern Europe come from Happisburgh, in the county of Norfolk, in the east of England, where footprints and stone tools dating back 900,000 years have been found. At that time, there was a predominance coniferous forests accompanied by cold winters similar to those in southern Scandinavia today. The data does not seem to indicate that the hominids remained in the place for a long time, which suggests that they did not have the opportunity to adapt physically.
How these hominoid primates survived harsh conditions so different from those in their remote African homelands remains a mystery. In the area there are no caves or remains of places to shelter. The Happisburgh artifacts are simple, indicating the absence of complex technology.
Evidence for the existence of Deliberate bonfires in that era are controversial. The tools to make garments adapted to the body and resistant to the weather they do not appear in western Europe until almost 850,000 years later. Many animals migrate to avoid seasonal cold, but Happisburgh hominids they would have had to move about 500 miles south for the difference to be significant.
It is hard to imagine that these beings survived the ancient Norfolk winters without fire or warm clothing. However, the fact that there would be hominids that far north it means they had to find a way to resist the cold, so who knows what archaeologists will find in the future.
The Boxgrove Hunters
Sites from more recent settlements, such as Boxgrove in West Sussex, southern England, provide further clues as to how ancient hominids survived northern climates. The Boxgrove site it dates back almost 500,000 years, when the climate deteriorated to one of the coldest periods in human history.
We have strong evidence that those hominids hunted animals, from cut marks in bones to a horse’s shoulder blade probably pierced by a wooden spear. These findings are consistent with studies of current hunter-gatherer peoples, which show that those who live in colder areas depend more on the animals they hunt than those who live in warmer climates. The meat is rich in the calories and fats necessary to resist the cold.
Fossil tibia of a hominin from Boxgrove It is robust compared to modern humanswhich indicates that it belonged to a tall and stocky individual. the largest bodies with relatively short limbs decrease heat loss by minimizing surface area.
The optimal shape to prevent heat loss is the sphere. That is why animals and human beings from cold climates get as close as possible to it. Also, by this time there is clearer evidence of the existence of bonfires.
Cold weather specialists
The Neanderthals, inhabitants of Eurasia between approximately 400,000 and 40,000 years ago, lived in glacial climates. Compared to their African predecessors and to us they had short, stout limbs and broad, muscular torsos capable of producing and retaining heat.
However, its knobby face and hooked nose are the opposite of what might be considered adaptive in an ice age. Like Japanese macaques that live in cold areas and laboratory rats raised at low temperatures, current humans in cold climates they usually have a relatively high and narrow nose, and wide and flat cheekbones.
computer simulations of ancient skeletons indicate that the Neanderthal nose was more efficient than that of earlier species, adapted to higher temperatures, in conserving heat and moisture. It appears that the internal structure is as important as the overall size of the respiratory organ.
Even with their cold-adapted physiques, Neanderthals remained hostages to their tropical lineage. For example, they lacked the thick fur of other mammals from Glacier Europe, such as woolly rhinos or musk oxen. Instead, they developed a complex culture to survive.
We have archaeological evidence that they made garments and built shelters out of animal skins. The remains that show that they cooked and used fire to make a glue based on birch tar to make tools show sophisticated control of this heat source.
More controversial is the statement from some archaeologists that the bones of the first Neanderthals from the Sima de los Huesos site in Atapuerca, 400,000 years old, show seasonal deterioration due to the slowdown of metabolism to hibernate. The authors argue that the bones show disrupted growth and healing cycles.
Only a few primate species hibernate, such as some Madagascar lemurs and the lesser African bushbaby, as well as the pygmy slow loris of northern Vietnam.
This could suggest that humans can also hibernate. But most of the species that do it have a small body, with exceptions such as bears. Human beings are probably too big for that.
good for everything
The first fossils of the lineage Homo sapiens They date back 300,000 years and come from Morocco but until about 60,000 years ago we did not leave Africa to colonize all corners of the planet. This makes us relatively newcomers to most of the habitats we currently occupy. In the thousands of years since then, the inhabitants of icy places have biologically adapted to their environment, albeit on a small scale. A famous example of this adaptation is that in areas with little insolation, the Homo sapiens developing fair skin tones, better for synthesizing vitamin D. The genomes of present-day Greenlandic Inuit demonstrate their physiological adaptation to a high-fat marine diet, beneficial in cold environments. A more direct proof is provided by the DNA of 4,000-year-old hair preserved in the Greenland permafrost. The hair contains evidence of genetic changes that led to a stocky body shape that maximized heat production and retention, much like the Boxgrove hominin of which only one tibia remains.
Our tropical heritage means that we would still be unable to live in cold places if we had not developed ways to withstand the temperatures. For example, the traditional inuit parkawhich provides better insulation than the modern Canadian Army winter uniform.
The human ability to adapt through behavior was critical to our evolutionary success. Even compared to other primates, the physical adaptation of humans to the climate is slower. Adaptation through behavior is faster and more flexible than biological. Human beings are the summum of adaptive capacity, and we thrive in almost any ecological niche possible.
Laura Buck is Assistant Professor of Evolutionary Anthropology at Liverpool John Moores University.
Kyoko Yamaguchi is Senior Lecturer in Human Genetics at Liverpool John Moores University.
This article was originally published on The Conversation.
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