Evolution might stop humans from solving climate change

Central features of human evolution may stop our species from resolving global environmental problems like climate change, says a new study led by the University of Maine.

Humans have come to dominate the planet with tools and systems to exploit natural resources that were refined over thousands of years through the process of cultural adaptation to the environment. University of Maine evolutionary biologist Tim Waring wanted to know how this process of cultural adaptation to the environment might influence the goal of solving global environmental problems. What he found was counterintuitive.

The project sought to understand three core questions: how human evolution has operated in the context of environmental resources, how human evolution has contributed to the multiple global environmental crises and how global environmental limits might change the outcomes of human evolution in the future.

Waring's team outlined their findings in a new paper published in Philosophical Transactions of the Royal Society B. Other authors of the study include Zach Wood, UMaine alumni, and Eörs Szathmáry, a professor at Eötvös LorándUniversity in Budapest, Hungary.

Human expansion

The study explored how human societies' use of the environment changed over our evolutionary history. The research team investigated changes in the ecological niche of human populations, including factors such as the natural resources they used, how intensively they were used, what systems and methods emerged to use those resources and the environmental impacts that resulted from their usage.

This effort revealed a set of common patterns. Over the last 100,000 years, human groups have progressively used more types of resources, with more intensity, at greater scales and with greater environmental impacts. Those groups often then spread to new environments with new resources.

The global human expansion was facilitated by the process of cultural adaptation to the environment. This leads to the accumulation of adaptive cultural traits -- social systems and technology to help exploit and control environmental resources such as agricultural practices, fishing methods, irrigation infrastructure, energy technology and social systems for managing each of these.

"Human evolution is mostly driven by cultural change, which is faster than genetic evolution. That greater speed of adaptation has made it possible for humans to colonize all habitable land worldwide," says Waring, associate professor with the UMaine Senator George J. Mitchell Center for Sustainability Solutions and the School of Economics.

Moreover, this process accelerates because of a positive feedback process: as groups get larger, they accumulate adaptive cultural traits more rapidly, which provides more resources and enables faster growth.

"For the last 100,000 years, this has been good news for our species as a whole." Waring says, "but this expansion has depended on large amounts of available resources and space."

Today, humans have also run out of space. We have reached the physical limits of the biosphere and laid claim to most of the resources it has to offer. Our expansion also is catching up with us. Our cultural adaptations, particularly the industrial use of fossil fuels, have created dangerous global environmental problems that jeopardize our safety and access to future resources.

Global limits

To see what these findings mean for solving global challenges like climate change, the research team looked at when and how sustainable human systems emerged in the past. Waring and his colleagues found two general patterns. First, sustainable systems tend to grow and spread only after groups have struggled or failed to maintain their resources in the first place. For example, the U.S. regulated industrial sulfur and nitrogen dioxide emissions in 1990, but only after we had determined that they caused acid rain and acidified many water bodies in the Northeast. This delayed action presents a major problem today as we threaten other global limits. For climate change, humans need to solve the problem before we cause a crash.

Second, researchers also found evidence that strong systems of environmental protection tend to address problems within existing societies, not between them. For example, managing regional water systems requires regional cooperation, regional infrastructure and technology, and these arise through regional cultural evolution. The presence of societies of the right scale is, therefore, a critical limiting factor.

Tackling the climate crisis effectively will probably require new worldwide regulatory, economic and social systems -- ones that generate greater cooperation and authority than existing systems like the Paris Agreement. To establish and operate those systems, humans need a functional social system for the planet, which we don't have.

"One problem is that we don't have a coordinated global society which could implement these systems," says Waring, "We only have sub-global groups, which probably won't suffice. But you can imagine cooperative treaties to address these shared challenges. So, that's the easy problem."

The other problem is much worse, Waring says. In a world filled with sub-global groups, cultural evolution among these groups will tend to solve the wrong problems, benefitting the interests of nations and corporations and delaying action on shared priorities. Cultural evolution among groups would tend to exacerbate resource competition and could lead to direct conflict between groups and even global human dieback.

"This means global challenges like climate change are much harder to solve than previously considered," says Waring. "It's not just that they are the hardest thing our species has ever done. They absolutely are. The bigger problem is that central features in human evolution are likely working against our ability to solve them. To solve global collective challenges we have to swim upstream."

Looking forward

Waring and his colleagues think that their analysis can help navigate the future of human evolution on a limited Earth. Their paper is the first to propose that human evolution may oppose the emergence of collective global problems and further research is needed to develop and test this theory.

Waring's team proposes several applied research efforts to better understand the drivers of cultural evolution and search for ways to reduce global environmental competition, given how human evolution works. For example, research is needed to document the patterns and strength of human cultural evolution in the past and present. Studies could focus on the past processes that lead to the human domination of the biosphere, and on the ways cultural adaptation to the environment is occurring today.

But if the general outline proves to be correct, and human evolution tends to oppose collective solutions to global environmental problems, as the authors suggest, then some very pressing questions need to be answered. This includes whether we can use this knowledge to improve the global response to climate change.

"There is hope, of course, that humans may solve climate change. We have built cooperative governance before, although never like this: in a rush at a global scale." Waring says.

The growth of international environmental policy provides some hope. Successful examples include the Montreal Protocol to limit ozone-depleting gasses, and the global moratorium on commercial whaling.

New efforts should include fostering more intentional, peaceful and ethical systems of mutual self-limitation, particularly through market regulations and enforceable treaties, that bind human groups across the planet together ever more tightly into a functional unit.

But that model may not work for climate change.

"Our paper explains why and how building cooperative governance at the global scale is different, and helps researchers and policymakers be more clear-headed about how to work toward global solutions," says Waring.

This new research could lead to a novel policy mechanism to address the climate crisis: modifying the process of adaptive change among corporations and nations may be a powerful way to address global environmental risks.

As for whether humans can continue to survive on a limited planet, Waring says "we don't have any solutions for this idea of a long-term evolutionary trap, as we barely understand the problem." says Waring.

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A life less obvious: Study sheds light on the evolution of underground microbes

Deep, dark fractures reaching far down into the oldest rocks on Earth may seem about as hospitable to life as outer space, but some estimates suggest that microbes dwelling deep in the Earth's crust account for the majority of microbial life. These underground lifeforms, which make up what's known as the deep biosphere, could account for as much as 20% of all biomass on Earth.

These ecosystems host microbial lineages that are of interest for understanding the origin and evolution of life on our planet but remain the least explored and understood ecosystems on Earth, according to the authors of a new study that takes a closer look at how deep habitats changed during Earth's tumultuous past.

"Understanding the history of the deep biosphere can provide insight into the evolution of life on Earth," said Peter Reiners, a professor of geosciences and associate dean of the University of Arizona College of Science, who co-authored the paper with Henrik Drake, an associate professor at the Linnaeus University in Sweden. "This requires understanding the complex evolution of habitable conditions in these underground environments, but such assessment had not been presented until now."

While microbes have been known to eke out a living as deep as 3 miles below Earth's surface, and possibly beyond, very little is known about how the deep biosphere has evolved over geologic history, and how modern microbes are related to their ancient ancestors in the subsurface.

Reiners and Drake focused on Precambrian cratons, which are some of the oldest rocks still present today, to find out where and when subsurface microbes should have been active on Earth hundreds of millions to billions of years ago. The results of their study, published this week in the Proceedings of the National Academy of Sciences, reveal that many cratons were uninhabitable for microbes for much of their existence, with the longest period of habitability not much beyond a billion years, and many cratons have only been habitable for the past 50 million to 300 million years.

"We showed that because microbial habitability generally requires temperatures less than about 100 degrees Celsius (212 degrees Fahrenheit), in only a few places do we expect to find evidence of subsurface microbial life older than about a billion years," Reiners said. "Just because these rocks are really old, and the fluids in them may be old, too, doesn't mean that they could've supported life until relatively recently, when they got very close to the surface by erosion."

Precambrian cratons are home to microorganisms that get their energy from consumption of nutrients including sparsely available organic carbon but also from chemical reactions between fluids and rocks. Drake and Reiners estimate that subsurface bacteria and archea (single-celled prokaryotes similar to bacteria), which now compose up to 90% of all microbial life on Earth, probably composed an even larger fraction of total life hundreds of millions to billions of years ago.

"Their evolution, particularly the evolution of their metabolisms -- how they get energy and what chemical elements they 'eat' and 'poop' -- provide key insights into the evolution of all other critters," Reiners said, adding that some researchers think that life may have first evolved beneath Earth's surface.

The researchers used a combination of records of deep ancient life found within craton fractures and recent advances in intermediate- and low-temperature thermochronology, a technique that allows scientists to reconstruct the temperature histories of rocks. Rocks may have endured higher temperatures and pressure during periods when sediments accumulated on top of them, only to be brought closer to the surface and into more habitable conditions once those sedimentary layers eroded away.

"By combining thermochronologic results from several different radioisotopic dating systems, we can reconstruct their thermal histories through the ups and downs of burial and erosion over time," Reiners said. "This approach gives us context for prospecting and interpreting the little-explored geologic record of the deep biosphere of Earth's cratons."

By assessing when these rock environments became habitable, and in some cases when they may have been buried and sterilized again, the study provides new insights into the evolutionary aspect of the deep biosphere.

"Cratonic rocks formed billions of years ago, often deep in the crust, at temperatures too high for any life," Reiners said. "It was only much later, following erosion, that the currently exposed rocks reached levels in the crust where temperatures were habitable."

Drake said thermochronology could help identify areas where researchers could look for the oldest records of subsurface microorganisms on Earth.

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Earth-like biospheres on other planets may be rare

A new analysis of known exoplanets has revealed that Earth-like conditions on potentially habitable planets may be much rarer than previously thought. The work focuses on the conditions required for oxygen-based photosynthesis to develop on a planet, which would enable complex biospheres of the type found on Earth. The study is published today in Monthly Notices of the Royal Astronomical Society.

The number of confirmed planets in our own Milky Way galaxy now numbers into the thousands. However planets that are both Earth-like and in the habitable zone -- the region around a star where the temperature is just right for liquid water to exist on the surface -- are much less common.

At the moment, only a handful of such rocky and potentially habitable exoplanets are known. However the new research indicates that none of these has the theoretical conditions to sustain an Earth-like biosphere by means of 'oxygenic' photosynthesis -- the mechanism plants on Earth use to convert light and carbon dioxide into oxygen and nutrients.

Only one of those planets comes close to receiving the stellar radiation necessary to sustain a large biosphere: Kepler-442b, a rocky planet about twice the mass of the Earth, orbiting a moderately hot star around 1,200 light years away.

The study looked in detail at how much energy is received by a planet from its host star, and whether living organisms would be able to efficiently produce nutrients and molecular oxygen, both essential elements for complex life as we know it, via normal oxygenic photosynthesis.

By calculating the amount of photosynthetically active radiation (PAR) that a planet receives from its star, the team discovered that stars around half the temperature of our Sun cannot sustain Earth-like biospheres because they do not provide enough energy in the correct wavelength range. Oxygenic photosynthesis would still be possible, but such planets could not sustain a rich biosphere.

Planets around even cooler stars known as red dwarfs, which smoulder at roughly a third of our Sun's temperature, could not receive enough energy to even activate photosynthesis. Stars that are hotter than our Sun are much brighter, and emit up to ten times more radiation in the necessary range for effective photosynthesis than red dwarfs, however generally do not live long enough for complex life to evolve.

"Since red dwarfs are by far the most common type of star in our galaxy, this result indicates that Earth-like conditions on other planets may be much less common than we might hope," comments Prof. Giovanni Covone of the University of Naples, lead author of the study.

He adds: "This study puts strong constraints on the parameter space for complex life, so unfortunately it appears that the "sweet spot" for hosting a rich Earth-like biosphere is not so wide."

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