Climate and human evolution (2022)

Rick Potts is the director of the Smithsonian Institution’s Human Origins Program. He has researched human origins since the 1980s, and oversees the National Museum of Natural History’s What Does It Mean To Be Human? exhibition, which opened in 2010.

Dr. Rick Potts examines sediment cores. Image courtesy Smithsonian Institution.

Potts developed the variability selection hypothesis of human origins, linking key human traits to a process of adaptation to climate variability and uncertainty. Climate.gov interviewed Dr. Potts by telephone on September 29, 2016. Here are his lightly edited responses.

Climate.gov: What is variability selection?

Potts: Variability selection is a form of natural selection that explains adaptation as a response to dramatically increased variability in the environment. When climate and other aspects of the environment vary dramatically, it can really affect the survival and success of an organism and its offspring over time. The effects can be evident in the gene pool and adaptations of an organism over time. Ultimately, organisms that can cope with widely varying conditions have a better chance of surviving novel and unpredictable environments.

Climate.gov: How does variability selection explain human evolution better than other hypotheses?

Potts: For many years, the tradition among paleoanthropologists was to try to find the selective environment that drove human evolution, key traits such as walking upright, tool use, larger brains, language, complex innovations.

For a long time, the favored explanation was the savanna hypothesis: the drying out of Africa meant that early humans found themselves in arid grassland, and generation after generation there was pressure to adapt to that drying trend.

(Video) Human Evolution and Climate Change

Paleoanthropologists long suspected that human evolution occurred primarily in grassland environments, in landscapes such as Tarangire National Park, Tanzania. Image courtesy Wikipedia user: ProfessorX.

Variability selection offers a different explanation. Over time and in different places where our ancestors lived, environments varied widely. Variability selection proposes that major features of human evolution were actually ways that our ancestors became more adaptable.

It’s a process of selection and adaptation to environmental variability, and it accounts for traits that cannot be explained by adaptation to any one environment or trend. For example, our large brains are useful for processing a wide range of information, our teeth and ability to make tools are useful for consuming a wide variety of foods, our sociability helps us team up with others when our survival is threatened.

Climate.gov: When and how did you conceive of variability selection?

Potts: I first thought about variability selection doing fieldwork in East Africa, in southern Kenya, in the mid-1980s.

At the time, I was a total proponent of the savanna hypothesis. I was working at the site of Olorgesailie, a sedimentary basin that preserves a million-year period. As I worked there, walking up and down the hillsides, studying the sediments, I saw in the rock record the presence of a large lake stretching across the basin. Then the lake was gone, then a volcanic eruption disrupted the environment that had been there, then the lake was back, followed by a severe drought, then the lake was back again.

This excavated pit shows different sediment layers at Sediment layers from Olorgesailie. Image courtesy Smithsonian Institution.

So it was clear the environment changed substantially and repeatedly over this million-year period. It wasn’t a stable environment, and it wasn’t a trend in one direction.

I also saw, over the first couple years of research there, that the dominant mammals preserved as fossils—zebras, elephants, pigs—were specialized grazing animals of the savanna, well adapted to a grassland environment. But they went extinct about a half a million years ago. They were survived by relatives that were smaller and capable of changing their diet.

The more adaptable animal lineages were able to survive while their specialized relatives became extinct. It was a real problem for the continual-drying-out hypothesis. And I hit myself in the head and said, “You’re an anthropologist. Maybe this is relevant to human origins.” So I delved into environmental science.

For a long time, paleoanthropologists looked at the data and saw the drying-out signal, and explained the overall variability signal as noise. I realized that the ramping up of variability wasn’t noise; it was also a signal, and an important one. The fluctuations between dry and wet conditions could pose a challenge to the survival of animals. My new background in environmental science helped inform my paleoanthropological research.

(Video) Climate Affected Pre-Human Habitats & Evolution

Climate.gov: What evidence shows increasing climate variability over the past several million years?

Potts: Oxygen isotopes in the shells of foraminifera in deep-sea cores are one line of evidence. Sapropels are another. In the eastern Mediterranean, you find dark and light bands in deep-sea cores that indicate periods of very strong rainfall followed by drought in Africa. I could see in these sorts of records that relative stability was followed by periods of instability. That has led me to the latest work that I've done on variability selection, which focuses on Earth's orbital cycles affecting the amount of solar radiation reaching tropical Africa and the intensity of rainfall.

Left: Fossil planktonic foraminifera (33-50 million years old) from Tanzania. Photo by Paul Pearson, Cardiff University, Creative Commons License. Right: Lake Zhitkovichi dries near Cervone in Belarus, creating a dark sapropel layer. Photo by Peter Philo, Gomel Today.

The sapropel record is clearest over the past 5 million years, and there’s a record of windblown dust off the East African coast that goes back even longer. These provide an excellent record of change. The Smithsonian has also undertaken a drilling project at Olorgesailie, drilling a sediment core until we reached volcanic rock at the local base of the Rift Valley.

The drill core spans a million years, and parts of the record are detailed enough to preserve records of individual seasons. This is a great breakthrough because now we can examine a detailed record of environmental change at the same site where we’ve already documented major changes in human evolutionary adaptation based on evidence of the fossils and artifacts we’ve excavated.

This graph shows milestones in human evolution correlated with climate variability. Milestones indicated along the bottom of the graph show hominin origins; habitual bipedality; first stone toolmaking, eating meat/marrow from large animals; onset of long-endurance mobility; onset of rapid brain enlargement; and expansion of symbolic expression, innovation, and cultural diversity. Adapted from Smithsonian Institution.

Climate.gov: Can you give some examples of other species beside humans that have undergone variability selection?

Potts: I thought of variability selection when I became aware that the dominant savanna-grazing mammals of East Africa became extinct, replaced by more adaptable relatives, during periods of highly variable environment.

One example involves baboons. The long-persisting baboon of East Africa was the large Theropithecus. It was a specialized grazing animal. We can see the wear marks on the chewing surfaces of the teeth where grass wore down the teeth over a baboon’s lifetime. Over time, the lineage got bigger and bigger as a way of coping as best it could with tough, coarse grass, which was abundant. When grass was scarce, Theropithecus was very much competing with other organisms. Ultimately, the giant Theropithecus baboon went extinct about 500,000 years ago in southern Kenya and most of East Africa.

A relative of Theropithecus, the common baboon Papio, is still living. It evolved in a context of wider fluctuations. It’s not a specialized grazer. Its diet consists of just about anything a baboon can put into its mouth. It’s a more flexible animal, and it’s a survivor. As I was studying how Papio came to replace the once-dominant Theropithecus, the big question that came to my mind was how adaptability itself had evolved, and that’s a question biologists hadn’t dealt with effectively.

(Video) The Climate's Influence on Human Evolution

Climate.gov: How can an organism with a lifetime of 40 years “sense” or adapt to a change that is occurring over the span of thousands of years?

Potts: Individual animals do not evolve biologically. They can show a certain capacity to adjust to a changing environment. But the evolution of that capacity—the adaptability of the organism—evolves in a population over time. Sexual reproduction allows DNA to be remixed every generation, creating slightly different genetic makeups to be “tested” against the environment. If these new genomes allowed individuals greater flexibility in nutrition or behavior, they would, according to the variability section hypothesis, provide a survival advantage in new or variable environments. Even if the advantages were small, over many generations the genetic makeups that favored them would become widespread.

So, variability selection is a process where combinations of interacting genes, and the genes that enable flexible interactions with the environment, are favored. This process promotes adaptability. The idea or variability selection is that the evolution of adaptability can’t take place in an animal’s lifetime, or in a relatively stable or directionally changing environment. Rather the genetic changes that yield flexible environmental responses are built up in eras of instability in the surroundings.

Nicknamed Mrs. Ples, this hominin fossil skull belongs to the species Australopithecus africanus, and is held in the collections of the Ditsong Museum of Natural History, Pretoria, South Africa. Photo by Michon Scott.

Climate.gov: How has variability selection been received by other anthropologists?

Potts: Earth scientists embraced variability selection quickly because Earth scientists see climate and other types of environmental records as relevant to understanding and explaining a particularly compelling case of evolution—our own.

Geneticists were reluctant at first to embrace the idea because the concept of natural selection [to a specific environment] is mathematically well tested. In other words, we understand very well how an organism can evolve to become well matched to a certain type of environment—reliant on specific foods, a particular range of temperature or rainfall, or having well defined interactions with other species.

While this foundation of natural selection is well tested, it doesn’t answer how a population or species may, in the long run, expand its adaptive options and enlarge the range of habitats in which its gene pool can thrive. Variability selection is meant to fill that gap in our understanding. It posits that variability in the environment can also be an agent of natural selection—one where adaptability is the favored response.

This graph correlates changes in climate to changes in hominin brain size. Adapted from the Smithsonian Institution.

Flexibility may indeed be difficult to evolve, since what can possibly favor adaptability in an environment that is relatively stable for some period of time? The latest tests of the idea look at the fossil record, and they show that major milestones in human evolution occurred during the most prolonged periods of instability in African climate history.

(Video) How a Changing Climate Drove Early Humans Out of Africa

My paleoanthropology colleagues were at first split, some embracing it, and others reluctant to include anything new in their teaching. But the hypothesis is 20 years old now, and by now, many of my colleagues talk about the environments (plural) of our ancestors. It’s a small shift in terminology but a significant shift in outlook.

Climate.gov: How is future climate change likely to affect human evolution?

Potts: It is our survival challenge for the future. I think it’s going to present some of the same kinds of challenges our ancestors faced: vastly changed landscapes, and ways of life that may no longer be able to thrive or even exist. It will continue to test how flexible and adaptable humans are.

For more information, see the Smithsonian Institution’s statement on climate change.

Further reading

Campisano, C.J. (2012). Milankovitch cycles, paleoclimatic change, and hominin evolution. Nature Education Knowledge, 4(3), 5.

Potts, R. (1998). Variability selection in hominid evolution. Evolutionary Anthropology, 7(3), 81–96. doi: 10.1002/(SICI)1520-6505(1998)7:3<81::AID-EVAN3>3.0.CO;2-A.

Potts, R., Faith, J.T. (2015). Alternating high and low climate variability: The context of natural selection and speciation in Plio-Pleistocene hominin evolution. Journal of Human Evolution, 87, 5–20. doi: 10.1016/j.jhevol.2015.06.014.

Potts, R., Sloan, C. (2010). What Does It Mean To Be Human? National Geographic, Washington, DC.

Smithsonian Newsdesk. (2014, October 2). Smithsonian Statement on Climate Change.

What Does It Mean to Be Human? The Age of Humans: Evolutionary Perspectives on the Anthropocene. Smithsonian National Museum of Natural History. Last updated October 13, 2016.

What Does It Mean to Be Human? Climate effects on human evolution. Smithsonian National Museum of Natural History. Last updated November 8, 2016.

FAQs

What is the relationship between climate and human evolution? ›

Two different types of environment – dense woodlands and open bushland – occurred in the same areas of East Africa during the period of human evolution. Climate fluctuation altered the proportion of these habitats, and thus led to repeated changes only in population density and variable conditions of natural selection.

How does climate influence evolution? ›

Environmental conditions such as rising temperatures can affect both the way selection acts on a trait and the expression of genes controlling it. If the environmental effect strengthens selection or increases the genetic variance, then the rates of evolution should be accelerated.

What kind of climate did humans evolve in? ›

Paleoanthropologists long suspected that human evolution occurred primarily in grassland environments, in landscapes such as Tarangire National Park, Tanzania.

How have humans adapted to changing climates? ›

Humans can adapt to climate change by reducing their vulnerability to its impacts. Actions such as moving to higher ground to avoid rising sea levels, planting new crops that will thrive under new climate conditions, or using new building technologies represent adaptation strategies.

How did climate change affect early people? ›

Climate Change Some of the biggest human migrations coincided with major changes in climate, according to a new analysis. Researchers say early humans set out in search of climates where more food was available. And some populations stayed put in certain locations because barriers like glaciers blocked their progress.

How does climate change affect natural selection? ›

Our results show that climate both induces phenotypic responses and alters natural selection, and that the change in the optimal phenotype might be either weaker, as for spring temperature, or stronger, as for precipitation, than the optimal response.

What factors influence human evolution? ›

Five different forces have influenced human evolution: natural selection, random genetic drift, mutation, population mating structure, and culture. All evolutionary biologists agree on the first three of these forces, although there have been disputes at times about the relative importance of each force.

How evolution affects our life today? ›

Evolution is present in our daily lives, like when we catch or combat the flu virus. Evolution also plays a role in some of our most pressing global health problems. The human immunodeficiency virus (HIV), for instance, evolves faster than the immune system can keep up with it.

Are humans influencing the process of evolution? ›

Most scientists would agree unequivocally that humans have greatly affected the process of evolution, from the rise of antibiotic and pesticide resistance to the largely human-caused increase in the extinction rate. Our effect on the process of evolution even extends to our own species' evolution.

How did the changing climate affect the life of humans Class 6? ›

Answer: When the climate of the world was changing, people observed places where edible plants are found, about seeds, plants, etc. They started growing their own plants. And thus, they became farmers.

What impact do humans have on the environment? ›

Humans impact the physical environment in many ways: overpopulation, pollution, burning fossil fuels, and deforestation. Changes like these have triggered climate change, soil erosion, poor air quality, and undrinkable water.

What are three ways humans adapt to their environment? ›

Humans adapt to changes in the environment by genetic change, developmental adjustments, acclimatization, and cultural or technological advances.

Why do we need to adapt to climate change? ›

Beyond doing everything we can to cut emissions and slow the pace of global warming, we must adapt to climate consequences so we can protect ourselves and our communities. The fallout varies depending on where you live. It might mean fires or floods, droughts, hotter or colder days or sea-level rise.

What impacts will climate change have in the developing world? ›

Climate change aggravates the effects of population growth, poverty, and rapid urbanisation. Without serious adaptation, climate change is likely to push millions further into poverty and limit the opportunities for sustainable development and for people to escape from poverty.

How can we reduce the impact of climate change? ›

  1. Put a price on carbon.
  2. End fossil fuel subsidies.
  3. Build low-carbon, resilient cities.
  4. Increase energy efficiency and use of renewable energy.
  5. Implement climate-smart agriculture and nurture forest landscapes.
18 Mar 2015

How did the environment affect early human life? ›

Humans began to work with and occasionally against their environment to create a stable way to acquire food as well as a more stable lifestyle. On the other hand, the environment, the climate in particular, definitely dictated the movement and survival methods of early humans.

What are the 3 major changes in human evolution? ›

The evolution of modern humans from our hominid ancestor is commonly considered as having involved four major steps: evolving terrestriality, bipedalism, a large brain (encephalization) and civilization.

What was the impact of ice on human evolution? ›

The Ice Age lowered the sea levels and gave Homo sapiens the opportunity to spread far and wide across the world. The colder periods made humans evolve into larger and more insulated bodies.

Are humans evolving due to climate change? ›

Global warming will likely alter the internal workings of our bodies — and cause a noticeable shift in our appearance. As climate change brings rising temperatures, droughts, shifting patterns of precipitation and longer growing seasons, plants and animals are evolving to keep pace.

Does climate change speed up evolution? ›

The genomes of these populations will be differently adapted to the local environment. 'So if and when the climate changes, if it gets warmer, it is beneficial if you have gene flow from the south, to maintain a population. 'In effect, evolution is being speeded up.

Can humans and animals adapt to climate change? ›

Climate Change Is Causing Some Animals To Grow Larger Limbs And Beaks Just like humans, researchers say animals also have to adapt to climate change. The shifts for some warm-blooded animals are occurring over a far shorter time period than would usually happen.

What is the importance of human evolution? ›

The study of the evolution of the human species can provide insight to understanding the violence, aggression and fear around us today. Humans have evolved as social, empathetic, collaborating and altruistic beings in small groups sharing common identities.

How will humans evolve in future? ›

We will likely live longer and become taller, as well as more lightly built. We'll probably be less aggressive and more agreeable, but have smaller brains. A bit like a golden retriever, we'll be friendly and jolly, but maybe not that interesting. At least, that's one possible future.

What can you say about the human evolution? ›

Human evolution is the lengthy process of change by which people originated from apelike ancestors. Scientific evidence shows that the physical and behavioral traits shared by all people originated from apelike ancestors and evolved over a period of approximately six million years.

Does evolution affect our way of living and our planet Earth Why? ›

"Evolution will fundamentally alter how species and ecosystems respond to environmental change," Hendry says. "Evolution therefore needs to be an integral part of our assessments of biodiversity and ecosystem services."

Are humans evolving right now? ›

Genetic studies have demonstrated that humans are still evolving. To investigate which genes are undergoing natural selection, researchers looked into the data produced by the International HapMap Project and the 1000 Genomes Project.

How can evolution cause changes in population? ›

Evolution by genetic drift causes changes in populations by chance alone. Evolution by genetic drift occurs when the alleles that make it into the next generation in a population are a random sample of the alleles in a population in the current generation.

What are 10 ways humans impact the environment? ›

At least, you need to be aware of all the factors that contribute to this state and share the knowledge.
  • Overpopulation. Source: Diy13/iStock. ...
  • Pollution. Source: zeljkosantrac/iStock. ...
  • Global Warming. ...
  • Climate Change. ...
  • Genetic Modification. ...
  • Ocean Acidification. ...
  • Water Pollution. ...
  • Overfishing.
22 Jun 2020

What happens if there is no evolution? ›

Evolution is the key to the life on earth. Without evolution there would be no variability there will be no inheritance of character from the parents to offspring. Since there would be no evolution there would be be no replication hence all the plants eventually die and also all the animals should eventually die.

What role should humans play in the ecosystem? ›

Humans are an integral part of ecosystems. Ecosystems provide a variety of benefits to people, including provisioning, regulating, cultural, and supporting services. Provisioning services are the products people ob- tain from ecosystems, such as food, fuel, fiber, fresh water, and genetic resources.

What are the 3 major changes in human evolution? ›

The evolution of modern humans from our hominid ancestor is commonly considered as having involved four major steps: evolving terrestriality, bipedalism, a large brain (encephalization) and civilization.

How did the changing climate affect the life of humans Class 6? ›

Answer: When the climate of the world was changing, people observed places where edible plants are found, about seeds, plants, etc. They started growing their own plants. And thus, they became farmers.

What was the impact of ice on human evolution? ›

The Ice Age lowered the sea levels and gave Homo sapiens the opportunity to spread far and wide across the world. The colder periods made humans evolve into larger and more insulated bodies.

What causes human evolution? ›

Five different forces have influenced human evolution: natural selection, random genetic drift, mutation, population mating structure, and culture. All evolutionary biologists agree on the first three of these forces, although there have been disputes at times about the relative importance of each force.

How human will evolve in the future? ›

We will likely live longer and become taller, as well as more lightly built. We'll probably be less aggressive and more agreeable, but have smaller brains. A bit like a golden retriever, we'll be friendly and jolly, but maybe not that interesting. At least, that's one possible future.

How has human evolution impacted the world? ›

Numerous examples of this human-induced contemporary evolution have been reported in a number of 'contexts', including hunting, harvesting, fishing, agriculture, medicine, climate change, pollution, eutrophication, urbanization, habitat fragmentation, biological invasions and emerging/disappearing diseases.

What is human evolution how it explain? ›

Human evolution is the lengthy process of change by which people originated from apelike ancestors. Scientific evidence shows that the physical and behavioral traits shared by all people originated from apelike ancestors and evolved over a period of approximately six million years.

What is the role of climate in human life? ›

Key facts. Climate change affects the social and environmental determinants of health – clean air, safe drinking water, sufficient food and secure shelter. Between 2030 and 2050, climate change is expected to cause approximately 250 000 additional deaths per year, from malnutrition, malaria, diarrhoea and heat stress.

Who is most affected by climate change? ›

The most vulnerable groups, including children, the elderly, people with preexisting health conditions, outdoor workers, people of color, and people with low income, are at an even higher risk because of the compounding factors from climate change.

How does the climate influence the lifestyle of people? ›

With a change in season, there is a change in food habits and clothing. There are also changes in the variety of crops and fruits grown. People also take a break from their regular routines in the form of vacations.

Are humans evolving due to climate change? ›

Global warming will likely alter the internal workings of our bodies — and cause a noticeable shift in our appearance. As climate change brings rising temperatures, droughts, shifting patterns of precipitation and longer growing seasons, plants and animals are evolving to keep pace.

How did the environment affect early human life? ›

Humans began to work with and occasionally against their environment to create a stable way to acquire food as well as a more stable lifestyle. On the other hand, the environment, the climate in particular, definitely dictated the movement and survival methods of early humans.

What are three ways humans adapt to their environment? ›

Humans adapt to changes in the environment by genetic change, developmental adjustments, acclimatization, and cultural or technological advances.

Are humans evolving right now? ›

Genetic studies have demonstrated that humans are still evolving. To investigate which genes are undergoing natural selection, researchers looked into the data produced by the International HapMap Project and the 1000 Genomes Project.

Why is evolution important? ›

They have led to major improvements in living standards, public welfare, health, and security. They have changed how we view the universe and how we think about ourselves in relation to the world around us. Biological evolution is one of the most important ideas of modern science.

When was the last human evolution? ›

Recent human evolution refers to evolutionary adaptation, sexual and natural selection, and genetic drift within Homo sapiens populations, since their separation and dispersal in the Middle Paleolithic about 50,000 years ago.

Videos

1. Climate Change Carbon Dioxide and Human Evolution During the Cambrian Explosion
(Philosophical Investigations)
2. CARTA: Human-Climate Interactions and Evolution: Past and Future
(University of California Television (UCTV))
3. Human Origins: Climate Change and Human Evolution
(Smithsonian's National Museum of Natural History)
4. Climate Change Carbon Dioxide and Human Evolution during the GOBE Biodiversification Event
(Philosophical Investigations)
5. CARTA: Climate and Evolution: Peter deMenocal: African Climate Change and Human Evolution
(University of California Television (UCTV))
6. Seven Million Years of Human Evolution
(American Museum of Natural History)

Top Articles

You might also like

Latest Posts

Article information

Author: Manual Maggio

Last Updated: 12/01/2022

Views: 6083

Rating: 4.9 / 5 (69 voted)

Reviews: 92% of readers found this page helpful

Author information

Name: Manual Maggio

Birthday: 1998-01-20

Address: 359 Kelvin Stream, Lake Eldonview, MT 33517-1242

Phone: +577037762465

Job: Product Hospitality Supervisor

Hobby: Gardening, Web surfing, Video gaming, Amateur radio, Flag Football, Reading, Table tennis

Introduction: My name is Manual Maggio, I am a thankful, tender, adventurous, delightful, fantastic, proud, graceful person who loves writing and wants to share my knowledge and understanding with you.