Introduction

Climate change is a big topic today, but did you know that it also played a huge role in shaping human evolution millions of years ago? That’s right! The history of our ancestors is closely linked to the changing environment of the Earth. In this blog post, we’ll explore how past climate changes influenced the development and dispersal of human species, how our ancestors adapted to these changes, and what these ancient climates can teach us about our future. By the end of this post, you’ll have a better understanding of how climate has been a driving force in human history and why it’s so important for us to pay attention to it today.

1. The Basics of Climate Change and Human Evolution

Let’s start with the basics. Climate change refers to significant changes in the Earth’s climate over long periods. This includes changes in temperature, precipitation (rain, snow, etc.), and wind patterns. These changes can happen naturally over thousands or even millions of years. For instance, volcanic eruptions, changes in the sun’s energy, and shifts in the Earth’s orbit have all affected the climate in the past.

Human evolution, on the other hand, is the process by which we humans have developed from our earliest ancestors over millions of years. Scientists study human evolution by examining fossils (the preserved remains of ancient humans) and ancient tools and by analyzing the genetic material found in bones.

But how are climate change and human evolution connected? Well, changes in climate have forced our ancestors to adapt to new environments, find new food sources, and even develop new skills. These adaptations were crucial for survival and played a key role in shaping who we are today.

2. Climate Changes and the Evolution of Early Humans

The story of human evolution is, in many ways, a story of climate change. Let’s take a journey back in time to explore some of the key moments in this story.

The Great Rift Valley and Early Hominins

One of the most important regions for studying human evolution is the Great Rift Valley in East Africa. This area is often referred to as the “Cradle of Humankind” because it has produced so many important fossils. Millions of years ago, this region experienced significant geological changes, including volcanic activity and shifts in the Earth’s tectonic plates. These changes created a variety of environments, from forests to savannas (grasslands).

About 2 to 3 million years ago, during a period known as the Pliocene, the climate in East Africa began to shift from a wetter environment to a drier one. This change had a massive impact on the landscape, turning dense forests into open grasslands. Early human ancestors, known as hominins, had to adapt to these new conditions.

One of the most famous hominins, Australopithecus afarensis, lived around this time. “Lucy,” a well-known fossil of this species, was discovered in Ethiopia in 1974. Lucy and her relatives had to adapt to life in a more open environment, which may have encouraged them to walk upright on two legs, or become bipedal. Walking on two legs would have helped them see over tall grasses, spot predators, and carry food or tools.

The Ice Ages and Human Migration

Fast forward to about 2 million years ago, and we find ourselves in a period known as the Pleistocene. This time is often called the “Ice Ages” because it was marked by repeated glaciations (periods when large parts of the Earth were covered in ice). The Ice Ages had a significant impact on human evolution and migration.

As the climate cooled, some areas became too cold for early humans to survive, while others became more habitable. These shifts forced our ancestors to move, searching for food, water, and shelter. This period saw the migration of Homo erectus, an early human species, out of Africa and into Asia and Europe. These migrations were driven by the need to find new environments where they could survive as the climate changed.

The ability to adapt to different climates and environments was crucial for these early humans. They developed new tools and technologies, such as clothing made from animal skins, to protect themselves from the cold. They also learned to control fire, which provided warmth, protection from predators, and a new way to cook food.

3. How Climate Change Shaped Human Behavior and Culture

Climate change didn’t just influence where early humans lived; it also shaped how they lived. As environments changed, early humans developed new skills and behaviors to survive.

Adapting to New Environments

As mentioned earlier, the shift from forest to grassland environments in East Africa may have led to bipedalism in early hominins. But climate change also affected other aspects of human evolution, such as diet and social behavior.

For example, as the climate became drier and food sources changed, early humans had to become more versatile in their diets. Instead of relying solely on fruits and leaves from the forest, they started eating a wider range of foods, including meat from animals. This change in diet may have been crucial for brain development, as meat provides essential nutrients that support brain growth.

Climate change also influenced social behaviors. In harsh environments, cooperation and sharing became vital for survival. Early humans learned to hunt in groups, share food, and protect each other from predators. These social bonds may have been the foundation for the development of more complex societies.

The Role of Innovation and Technology

One of the most significant ways humans adapted to climate change was through innovation and technology. As new challenges arose, early humans developed new tools and techniques to overcome them.

For instance, during the Ice Ages, early humans in Europe and Asia created sophisticated tools for hunting and butchering animals. They also developed clothing and shelter to protect themselves from the cold. These innovations were crucial for survival in colder climates.

Another example is the use of fire. Learning to control fire was a game-changer for early humans. It provided warmth, a way to cook food, and protection from predators. Fire also allowed humans to extend their activities into the night, fostering social interactions and possibly even the development of language.

4. The Impact of Climate Change on Human Migration

One of the most significant ways climate change has influenced human evolution is through its impact on migration. Throughout history, humans have migrated in response to changing climates, moving to new areas where they could find food, water, and shelter.

The Out-of-Africa Migrations

The most famous example of climate-driven migration is the “Out-of-Africa” theory. This theory suggests that all modern humans (Homo sapiens) originated in Africa and then migrated out to other parts of the world. These migrations were likely driven by changes in climate that made some areas more hospitable than others.

As the climate shifted, some regions became arid and uninhabitable, pushing human populations to move. Other areas, like the Middle East, became greener and more welcoming, serving as stepping stones for humans migrating out of Africa.

This migration was not a single event but rather a series of waves over thousands of years. Each wave was likely driven by different climatic events, such as periods of intense drought or cooling.

Crossing the Bering Land Bridge

Another example of climate-driven migration is the crossing of the Bering Land Bridge, a land connection between Asia and North America that existed during the Ice Ages. Lower sea levels during glacial periods exposed this land bridge, allowing humans to migrate from Siberia into North America.

These migrations were driven by a combination of factors, including the search for new hunting grounds as large Ice Age animals like mammoths and bison moved across the landscape. Once in the Americas, human populations spread rapidly, adapting to a wide range of environments, from the Arctic tundra to tropical rainforests.

5. Lessons from the Past: What Ancient Climates Can Teach Us About Our Future

Studying how ancient humans adapted to climate change can provide valuable insights into our current situation. While we face different challenges today, the lessons of adaptability, innovation, and resilience remain just as relevant.

Adaptability and Resilience

One of the key lessons from human evolution is the importance of adaptability and resilience. Our ancestors survived by adapting to changing environments, developing new tools and technologies, and working together to overcome challenges. As we face the impacts of modern climate change, these lessons remind us of the importance of flexibility and innovation.

Learning from Past Mistakes

Another lesson from history is the importance of learning from past mistakes. Some human populations, like the Norse settlers in Greenland, failed to adapt to changing climates and ultimately perished. In contrast, Indigenous populations who adapted their lifestyles to the changing environment survived and thrived.

These examples highlight the importance of being willing to change and adapt. As we face the challenges of climate change today, we must be open to new ideas and solutions and learn from the experiences of others.

The Role of Technology and Innovation

Just as early humans used technology to adapt to new environments, we too can use technology to mitigate the impacts of climate change. From renewable energy sources like wind and solar power to advanced farming techniques that reduce greenhouse gas emissions, technology can play a crucial role in addressing the challenges of climate change.

6. Conclusion: The Ongoing Story of Human Adaptation (Continued)

As we face our own climate challenges today, we can draw inspiration from the resilience and adaptability of our ancestors. Just as they learned to thrive in new environments, developed new tools, and worked together to survive, we too have the capacity to innovate, adapt, and collaborate to create a sustainable future.

But we also have to remember the lessons of the past. Climate change today is happening at a much faster rate than ever before, largely due to human activities like burning fossil fuels and deforestation. This rapid change poses unprecedented challenges, and the stakes are higher than ever. Unlike in the past, where migration was a viable option, today we are bound by geopolitical borders, and there are fewer “new” places to migrate to.

This means that we must be even more creative, cooperative, and proactive in addressing climate change. It’s not just about surviving; it’s about thriving in a way that ensures the health of our planet and future generations.

By studying how ancient climates shaped human evolution, we gain not only a deeper understanding of our past but also valuable insights into how we can navigate the future. Our history is a testament to the power of human ingenuity and the will to survive. Now, it’s up to us to continue that legacy and rise to the challenges of our time with the same spirit of resilience and innovation.

In the end, the story of human evolution and climate change is a story of survival, adaptation, and hope. Let’s learn from our ancestors and make choices that will allow us to not only survive but to thrive in harmony with our ever-changing world.

Call to Action: What Can You Do?

As we learn from the past, it’s also important to think about what we can do today to help address climate change. Here are a few ways you can make a difference:

• Educate Yourself and Others: Learn more about climate change and its impacts. Share this knowledge with your friends and family. Understanding the issue is the first step toward making positive changes.

• Reduce Your Carbon Footprint: Simple actions like using less energy, recycling, and reducing waste can help reduce your carbon footprint. Consider walking, biking, or using public transportation instead of driving whenever possible.

• Support Sustainable Practices: Support businesses and products that are environmentally friendly and sustainable. Encourage your local community to adopt green practices.

• Advocate for Change: Get involved in your community and advocate for policies that address climate change. Your voice can make a difference!

By taking action today, we can help shape a future that is not only sustainable but also more equitable and just for all.

Remember: Just like our ancestors adapted to their changing world, we too have the power to adapt and create a better future. Let’s learn from the past, act in the present, and protect our planet for the generations to come.

Hair exclusively on the top of the head has become one of the defining characteristics of being human. As such a visible trait, it raises questions as to how and why it evolved this way. It is a long story, with questions of convergence and unique population stressors, but there is not a lot of research into the specifics, especially compared to other traits such as skin pigmentation. What we do know, so far, is that modern hair can tell a story of adaptation, gene flow and sexual selection. 

Homo erectus, 2 million years ago, had roughly the same body size and shape as modern humans, except for the brain. At some point during the following one million years, something happened that meant cranial capacity could expand hugely, paving the way for the larger brained specimens we are today. 

Many arguments have been put forward as to why; nutrition, fire, all may have played a part in the expansion of brain size, but one which is not covered as frequently is hair on the scalp. 

Running a large brain requires a lot of energy and produces extra heat in the head. Add to this the heat of the sun in Africa, and early humans were beginning to overheat. Sweat glands offered a way to cool down the body, but it came at the high price of water and precious electrolytes. Natural selection’s options were to restrict the size of the brain, which is what it had been doing so far, or find a new solution. 

The solution it found was curly hair. Scientists have examined the functionality of hair, especially curly hair, and found that it helps a great deal with thermoregulation. Having tight curls protects from the sun’s radiation and will keep the head cooler than if the head were bald. Straight and moderately curly hair protects as well, but not as efficiently as tight curls. They found that it was the layer of air between the coiled hair and scalp which created an extra layer of protection.  

And these coils not only protect from radiation, but minimise the amount of sweating an individual must do to cool to the same degree. In fact, bald men are found to sweat twice as much on their head to make up for the lack of hairy protection. In an environment where the sun is strong and water a precious resource, tight curls offer the perfect solution to overheating. 

With the evolution of tight curls of hair on the top of the head, the brain was protected from overheating and could continue to create the extra heat as the brain became larger. It also allowed humans to forage in the midday heat, unlike the predators of the time. 

We don’t know for sure the order of evolution here. Did curly hair occur after the loss of body hair, or did it evolve at the same time? Did it appear once, or convergently in multiple populations? Hopefully one day, more research into the evolution of hair can give us these answers. 

A few irregularities do crop up in the history of humans though. If having hair on our scalps is so important to thermoregulation, why is male baldness so prevalent? It is genetic and hair loss occurs in half of the male population by the time they are 50 years old. The answer may be more hair. The presence of beards may account for the loss of scalp hair. With both in place, thermoregulation becomes harder and overheating is a risk. By removing one section of hair, the head is back to its steady cooling. According to a study which compared balding rates in different ethnicities, white (British and Irish) men had the highest rates of complete balding, which makes sense in a land where radiation from the sun is not as strong and overheating due to the sun is less of an everyday issue. 

Across the globe, hair now exists in more than just tight curls, it ranges in shape, length and colour, and can be loosely tracked through populations. Gene flow contributes heavily to this distribution, but mutations have led to a few very interesting instances. 

In the Solomon Islands, a single random mutation created blonde hair in the island’s community. This single mutation was easily carried through the small population and now 10% of the population now has blonde hair, and 26% carry the recessive gene. This blonde hair occurred separately to the blonde hair found in Northern Europe and provides evidence that blonde colouration occurred at least twice in the evolution in human hair.  

But Europe is where we see a big range of colour and where most of the research into the evolution of hair has taken place. 

The theory of why there is so much variation here, and why it has been retained in the North and East, goes back to when humans first entered ige-age Europe. 35,000 years ago, hunter-gatherers were expanding into new territories in Eurasia. 20,000-15,000 years ago, the glacial maximum split the population in two, creating two very different environments. In the East, life continued as normal, and the risks involved in hunting remained unchanged. 

In the West, hunting was now risky and many males in a society with sexual division of labour did not make it back from long, dangerous hunting trips. This created an unequal balance of sex and while this often leads to a polygynous society, gathering in the tundra was scarce and males were unable to provide for more than one female, so monogamy became the only sustainable lifestyle for these groups. This meant that there was intense selection for the best mates from females. The theory goes that because of the restricted options, sexual selection was strong, and in this case, leant toward the “rarer” traits as they stood out more. In these populations, that meant lighter hair began to be specifically chosen and consequently spread throughout the continent. 

Based on research into the DNA which codes for hair, only red hair has been linked to lighter skin pigmentation, other colours seem to have no genetic benefit, suggesting it really was only sexual selection which made it so prolific in certain areas. 

Hair itself has become a powerful tool for many, for expressing identity, for concealing or displaying their power and an identifier to those around them. In fact 72% of women surveyed in North America say that they feel empowered when they feel good about their hair. However, there has been limited research into the evolution of hair, both the spread of certain colours and textures, and any genetic benefits to having diverse hair across the globe. It might be that the answer is a lifting of selection pressures and a move into sexual selection, but without investigation, we won’t know for sure. It seems like this defining trait which holds so much power to individuals deserves a little more explanation. 

Cabanac, M., & Brinnel, H. (1988). Beards, baldness, and sweat secretion. European Journal of Applied Physiology and Occupational Physiology, 58(1–2), 39–46. https://doi.org/10.1007/bf00636601

Frost, P. (2006). European hair and eye color: a case of frequency-dependent sexual selection?. Evolution and Human Behavior, 27(2), 85-103.

Lasisi, T., Smallcombe, J. W., Kenney, W. L., Shriver, M. D., Zydney, B., Jablonski, N. G., & Havenith, G. (2023). Human scalp hair as a thermoregulatory adaptation. Proceedings of the National Academy of Sciences, 120(24). https://doi.org/10.1073/pnas.2301760120

Loury, E. (2012, May 3). The Origin of Blond Afros in Melanesia. Science. https://www.science.org/content/article/origin-blond-afros-melanesia

Norkin, L. (2018, August 3). We Asked Women Across the Country All About Their Hair. In Style. https://www.instyle.com/beauty/splitting-hairs-survey-american-women-and-hair

Yildirim, A. M., Yousaf, A., Fang, W., & Kolodney, M. S. (2022, November). A cross-sectional study of male balding patterns in people of color. Journal of the American Academy of Dermatology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9511210/